The development of high-performance solid-state polymer electrolytes remains critical for enabling safe and durable lithium-ion batteries. In this work, PVA encapsulated Li7La3Zr2O12 (modified-LLZOPVA) was synthesized and confirmed through XRD, Raman analysis, and TEM. The modified-LLZOPVA powders were used as fillers in the PEO-LiCF3SO3 (O: Li ∼ 15) polymer matrix (PS15) to prepare an advanced composite electrolyte (CE) via a simple solution-casting approach. With a dc conductivity of 2.06 × 10−4 S cm−1, the optimised CE film (PS15 + 20 wt% modified-LLZOPVA), which is two orders of magnitude higher than the pristine polymer electrolyte (PS15) and one order higher than that containing unmodified LLZO. Finally, the electrochemical performance of the CE films, used as a separator-cum-electrolytes was evaluated in an all-solid-state Li-ion cell with LFP as the cathode. At 0.1C (60 °C), the LFP || PS15 + 20 wt% modified-LLZOPVA || Li cell provides a discharge capacity of 129.20 mA h g−1, a coulombic efficiency of 98.6%, and a capacity retention of 91.26%.On the other hand, under the same conditions, the LFP || PS15 || Li cell exhibits a lower discharge capacity of 80.01 mA h g−1, with 85.39% capacity retention and 95.2% coulombic efficiency. Moreover, the cell with the optimised PS15 + 20 wt% modified-LLZOPVA electrolyte demonstrates superior cycling stability, sustaining performance for up to 625 cycles, whereas the LFP || PS15 || Li cell maintains stability for only 280 cycles at 1C (60 °C). This study offers a valuable reference for the fabrication of composite electrolytes using simple processing routes while achieving high-voltage compatibility and superior performance.

NASICON-type Li+-ion-conducting solid electrolytes have emerged as promising materials for enabling safer and more stable solid-state lithium metal batteries (SSLMBs), thereby effectively addressing key challenges associated with conventional batteries that use flammable and thermally unstable liquid electrolytes. Among them, LAGP offers a favorable balance of structural stability, high ionic conductivity, and a wide electrochemical stability window, validating its viability as a promising solid electrolyte for SSLMBs. In this study, LAGP solid electrolyte was synthesized through a solid-state reaction at significantly lower temperatures (∼800 °C) than those employed in melt-quenching approaches (>1300 °C). The effects of calcination and sintering temperatures on the phase formation, hardness, density, and ionic conductivity of LAGP were investigated. LAGP sintered at 775 °C exhibited the highest ionic conductivity of 2.6 × 10−4 S cm−1, attributed to improved phase purity and densification. LSV measurements revealed a wide electrochemical stability window of 5.8 V vs. Li/Li+. A liquid-assisted solid-state lithium metal cell with an LFP/LAGP/Li configuration was assembled, delivering a discharge-specific capacity of 155 mA h g−1 at 0.1 C. Finally, XRD, XPS, and impedance measurements were performed after the rate studies to evaluate the stability of LAGP at the electrode interfaces.

Li-based solid electrolytes with the NASICON structure offer promising solutions for developing safer solid-state Li-ion batteries (SSLIBs) as potential alternatives to conventional LIBs that use liquid electrolytes, which are prone to safety risks, leakage, and thermal instability. LATP (Li1+xAlxTi2-x(PO4)3) solid electrolytes belong to the LMP [LiM2(PO4)3: M: Zr, Ti, and Ge] family of materials and are considered promising for large-scale SSLIB applications due to their low cost compared to LGP-based solid electrolytes and superior ionic conductivity relative to LZP-based solid electrolytes. In the present study, highly dense bare LTP and Al3+-doped LTP (LATP) were prepared using the solid-state reaction method, and their structural and transport behaviour were investigated by varying the Al3+ content (x = 0.2 to 0.4) and the sintering temperature (900–1100 °C). Conductivity measurements using impedance spectroscopy showed that Li1+xAlxTi2-x(PO4)3 with an x = 0.3 composition sintered at 1000 °C (0.3-LATP@1000), exhibits the highest ionic conductivity (7.2 × 10−5 S cm−1) at room temperature. The transport results of LATP solid electrolytes, with respect to different sintering temperatures and Al3+ dopant concentrations, were explained in terms of their crystal structure, relative density, and morphology. DC polarization measurements revealed that ions are the major charge carriers, while linear sweep voltammetry tests demonstrated excellent ESW with Li-metal, highlighting the potential of 0.3-LATP@1000 solid electrolyte for SSLIBs. Li stripping and plating measurements using a symmetric cell (Li/0.3-LATP@1000/Li) demonstrated good stability of the solid electrolyte for 500 h at a current density of 0.05 mA cm−2. Finally, SSLIB with the LFP/0.3-LATP@1000/Li configuration was demonstrated, exhibiting a discharge specific capacity of 158 mA h g−1 at 0.1C.

Na3V2(PO4)2F3 (NVPF) has recently been identified as a highly promising cathode material for sodium-ion batteries (SIBs) due to its outstanding structural stability, elevated operating voltage, and notable theoretical capacity. Despite its advantages, the electrochemical performance of this material is restricted by low electronic conductivity, and by fluorine loss during synthesis, which results in a low-voltage plateau around 3.4 V, thereby limiting its practical applications. In the present work, the stabilization of volatile fluorine was achieved by simply tuning the carbon coating on the NVPF surface. In situ carbon-coated NVPF (NVPF/C) materials were prepared through the sol–gel technique, with inexpensive citric acid as the carbon source. The carbon content was tuned by varying the molar ratios of vanadium in NVPF to citric acid; 2:1 (1 M NVPF/C), 2:1.5, 2:2, and 2:2.5. XRD patterns of the synthesized materials matched well with the reference pattern of NVPF (tetragonal, P42/mnm). The relative carbon content and elemental composition were determined using SEM-EDS; the carbon layer thickness was measured using HRTEM; and the degree of graphitization was assessed via Raman spectroscopy. Electrochemical analyses, including GCD, and differential capacity curves showed a low-voltage plateau around 3.4 V for 1 M NVPF/C. This plateau diminished with increasing carbon content, indicating fluorine stabilization at higher coating concentrations. The optimized carbon coating effectively suppressed fluorine loss, resulting in a significant reduction in charge-transfer resistance. 2 M NVPF/C exhibited discharge capacity of 113.9 mA h g–1 at 0.1 C and demonstrated excellent cycling performance, highlighting its strong potential for high-energy-density SIBs.

The development of safe, high-performance solid electrolytes is critical for advancing next-generation solid-state lithium-ion batteries (SSLIBs). Perovskite-type Li0.33La0.56TiO3 (LLTO) has emerged as a promising solid electrolyte for SSLIBs owing to its high thermal and mechanical stability; however, its moderate ionic conductivity and interfacial instability with lithium metal hinder its practical application. In this work, the ionic conductivity of LLTO was enhanced through A-site doping via partial substitution with Sr using two different Sr precursors (SrCO3 and SrF2). Sr-doped LLTO solid electrolytes were synthesised using a solid-state reaction method. Structural and microstructural analyses confirmed the successful incorporation of Sr into LLTO without the formation of secondary phases. Ionic conductivity measurements revealed that Sr-doped LLTO synthesised using the SrF2 precursor (LLTO-SrF2) exhibited higher ionic conductivity than that synthesised using the SrCO3 precursor (LLTO-SrCO3). The enhanced conductivity of LLTO-SrF2 relative to LLTO-SrCO3 and pristine LLTO was attributed to differences in their lattice parameters, densities, and microstructures. LLTO-SrF2 exhibited a high room-temperature bulk ionic conductivity of 2.86 × 10−3 S cm−1. To further address the interfacial instability with lithium metal, a PEO-based protective layer (PL) was placed around the LLTO-SrF2 pellet ((LLTO-SrF2)PL) to suppress parasitic reactions between Ti4+ and lithium metal while improving interfacial contact. The symmetric cell (Li/(LLTO-SrF2)PL/Li) exhibited stable galvanostatic cycling for over 540 h with highly reversible and symmetric lithium plating/stripping behaviour. These results highlight the synergistic effect of Sr substitution in enhancing ionic conductivity and polymer layer engineering in improving electrochemical stability against lithium metal.

Research on safe, high-energy density all-solid-state lithium batteries (ASSLBs) has been rapidly advancing to address the major safety and functional limitations of conventional batteries utilizing liquid electrolytes. The development of solid electrolytes with high ionic conductivity and a wide electrochemical stability window is therefore crucial for enabling high-performance ASSLBs. In this investigation, flexible polymer composite solid electrolyte (PCSE) membranes were fabricated via a solution casting method using a PEO polymer matrix with optimized LiTFSI salt content, and Li1.3Al0.3Ti1.7(PO4)3 (LATP) ceramic filler. The PCSE membrane containing 10 wt% LATP ceramic filler (10% LATP) exhibited an ionic conductivity of 0.19 × 10−3 S cm−1 at 60 °C. The electrochemical stability of the polymer membranes was assessed via lithium stripping-plating experiments at 0.1 mA cm−2. The 10% LATP PCSE membrane demonstrated notable stability for over 900 h without significant voltage fluctuations, confirming its superior interfacial robustness with lithium. The LFP/10% LATP/Li cell at 60 °C delivered a first cycle discharge capacity of 151.6 mAh g−1, compared to 143.4 mAh g−1 for the LFP/20% LiTFSI/Li cell at 0.1C. The cell also showed remarkable rate capability and cycling performance, retaining a high capacity of 103.9 mAh g−1 at 1C with 86.8% capacity retention after 150 cycles. Additionally, the optimized 10% LATP PCSE membrane was also tested with a high-voltage NMC622 cathode, demonstrating its potential applicability in high-voltage ASSLBs.

25Li2O-(10-x)GeO2-60SiO2-5Al2O3-xTiO2 (x = 1–5 mol%) samples namely T1-T5 were produced through the melt quenching method. X-ray Diffraction (XRD) studies recognized the amorphous and crystalline phases of samples. Among T1 to T5 samples, the T3 sample exhibited high glass-forming ability and thermal stability (ΔT = 173 °C), with high crystallization energy (273.89 kJ/mol) and low Avrami index. Mixed electronic-ionic conduction of samples was studied by employing the Small Polaron Hopping (SPH) model. DC ionic conduction of samples was studied by utilizing the Anderson and Stuart model. A novel approach was used to find strain energy in samples using shear moduli from the Makishima-Mackenzie model. The T3 sample had the lowest ionic conductivity (3.86 ×10−9 S/cm at 303 K), highest activation energy (0.808 eV), and exhibited a low (0.50 ×10−15 cm2 V−1 s−1 at 303 K) charge carrier mobility. These findings indicate that the optimized T3 sample is suitable for dielectric applications.

We synthesized biodegradable and economically viable solid-state electrolyte films based on konjac glucomannan (KG) and sodium iodide (NaI). Among the KGNaI-x (x = 31–69 wt%) films, KGNaI-69 exhibits superior flexibility, biodegradability, and sodium superionic conductivity of 77.9 mS cm−1. The KGNaI-69-based supercapacitor delivers outstanding electrochemical efficiency and cycling stability, retaining 84.4% capacitance after 5000 cycles establishing its potentiality toward flexible energy storage devices.

The present study demonstrates the structural, elastic, thermal, and electronic properties of copper nitride (Cu3N) doped with transition metal M (M: Fe, Co, and Ni) using pseudopotential-based density functional calculations as implemented in the Quantum ESPRESSO simulation code. The exchange-correlation is approximated by Perdew-Burke-Ernzerhof functional within the framework of generalized gradient approximation. The doped matrices, represented as Cu3NM, are verified to be stable structures, both thermodynamically and mechanically. Tailoring of elastic properties and their anisotropy due to M doping is successfully demonstrated through a comprehensive analysis of the computed elastic stiffness coefficients, elastic moduli, elastic anisotropy factors, and spatial variation of the elastic moduli, which have not been explored yet. An increase in bulk modulus due to M doping ensures enhanced mechanical stability under isotropic stress. Conversely, while doping of Co and Ni enhances the shear resistance of the host material, Fe doping slightly reduces it. The superior ductile nature of all the studied systems predicts their suitability for applications in flexible electronics. It is evident that doping of M substantially reduces the elastic anisotropy of Cu3N. Using the calculated elastic moduli, the velocity of acoustic waves and its anisotropy for Cu3N and Cu3NM are also predicted. The anisotropy in the acoustic velocity of the studied materials recommends their potential application in acoustic devices with directional selectivity. It is also noticed that, while the average acoustic velocity is reduced due to Fe doping, it increases for Co and Ni doping. Furthermore, analysis of the computed Debye temperature and minimum thermal conductivity forecasts their employability as thermal barrier coatings. Finally, the calculations reveal the ferromagnetic nature of Cu3NFe and Cu3NCo with respective induced magnetic moments of 2.71 and 1.47 μB/cell, recommending their potential applications in spintronics. It is also proved that the M-d-Cu-d coupling stabilizes the ferromagnetic ordering in such magnetic systems. On the other hand, Cu3NNi is observed to be non-magnetic.

The synthesis of 25 Li2O – 10 GeO2 – 60 SiO2 – 5 R (R = TeO2, SrO, SeO2, Tl2O, Al2O3) glasses was done by melt quenching technique. X-ray diffraction (XRD) studies confirmed the crystalline phases of synthesized samples after the heat treatment, which is also portrayed in Scanning Electron Microscope (SEM) images. Energy Dispersive Spectroscopy (EDS) depicted the presence of the elements used in the synthesis. Differential Scanning Calorimetry (DSC) curves evidenced ceramic nature of all samples, also their glass-forming ability and thermal stability, which are high for Al-doped sample. X-ray Photoelectron Spectroscopy (XPS) studies revealed the relative increment of BOs in the network of the Al-doped sample. Makishima–Mackenzie model was employed to calculate Young's modulus, bulk modulus, shear modulus, longitudinal modulus, Poisson's ratio, microhardness, fractal bond connectivity, average crosslink density, and bond number per unit volume of the samples. These findings indicated the notable mechanical properties of the Al2O3 mixed sample, owing to its large dissociation energy and high field strength. The optical band gap, index of refraction, molar polarizability, molar refractivity, metallization criterion, optical transmission, reflection loss, optical basicity, and electronic polarizability were calculated using the optical absorption studies. Fourier-Transform Infrared Spectroscopy (FTIR) studies of the synthesized samples revealed the presence of SiO4, LiO4, TeO3, TeO4, GeO4, AlO4, and AlO6 structural units in the glass ceramic matrix. From the impedance analysis, it was observed that the ionic conductivity of the glass ceramics containing 5 mol% of Al2O3, Tl2O is minimal (2.06 × 10−6 and 0.44 × 10−6 S/cm at 200 °C respectively) at all temperatures, indicating their suitability for dielectric applications. The maximum ionic conductivity (8.21 × 10−6 S/cm at 200 °C) of the TeO2 doped sample appraises its suitability for solid electrolytic applications.

Sodium-ion batteries (SIBs) are game-changing in large-scale energy storage technology compared to lithium-ion batteries (LIBs) due to abundant reserves, safety, and cost-effectiveness. However, serious issues in Mn-based P2-type cathodes, such as phase transitions, the Jahn-Teller effect, and Mn dissolution, hinder the success of SIBs. Herein, we report that altering the manganese oxide precursors in the solid-state synthesis of P2-type Na0.65Ni0.25Mn0.75O2 (NNMO) leads to structural variations and improvements in electrochemical properties. X-ray diffraction with refined data confirms that all samples are in the P2-type phase, with changes in lattice parameters and cell volume. Raman spectroscopy and electron spin resonance verify the presence of oxygen defects in the P2-type NNMO materials. Furthermore, X-ray photoelectron spectroscopy analysis of the Mn2O3 precursor-used Na0.65Ni0.25Mn0.75O2 (NNMO-2) sample reveals slightly higher Mn4+ and lower Mn3+ mixed valence states compared to other samples. The potential profile and dQ/dV plot of NNMO-2 exhibit solid-solution behavior, delivering an initial discharge capacity of 151 mAh/g and 152 mAh/g at 0.1 C. The sample demonstrates excellent capacity retention of 85.34% and 77.28% after 100 cycles at a 1 C rate, with a Coulombic efficiency exceeding 98% in both tested voltage ranges (1.5-4.0 V and 2.0-4.3 V), attributed to Mn charge compensation. Moreover, the Na-ion diffusion coefficient, estimated to be around 10-10 cm2/s using the galvanostatic intermittent titration technique and the reduced charge transfer resistance, confirmed by impedance measurements, further highlight the electrochemical benefits of the NNMO-2 sample. Overall, the results suggest that the Mn2O3 precursor can be a suitable raw material for solid-state reactions synthesizing P2-type Na0.65Ni0.25Mn0.75O2 cathode materials for sodium-ion battery applications.

Recent studies on batteries have drawn significant attention to all-solid-state fluoride-ion batteries (FIBs) as potential alternatives to the conventional Li-ion batteries because of their higher theoretical energy densities. On the solid electrolyte side, efforts are being made to develop a suitable material with improved ionic conductivity (∼ 10−3 S/cm) and enhanced electrochemical stability. SnF2-based solid electrolyte, BaSnF4 crystallizes in the PbSnF4 structure and is frequently considered as a potential solid electrolyte for FIBs operating at room temperature (RT). In this study, the conductivity results of BaSnF4 are influenced by doping with rare-earth ions (Ce3+) at different concentrations and by the synthesis methodology. The structural and transport behaviours of Ce3+-doped BaSnF4 solid electrolytes, prepared by mechanical milling and hydrothermal methods, are compared. The formation of the doped materials, which exhibit a tetragonal phase, is confirmed by X-ray diffraction. The presence of Ce3+ in the doped materials prepared by both methods is confirmed by their photoluminescence characteristics. Among the materials investigated in this study, 2 mol% Ce3+-doped BaSnF4, prepared by mechanical milling (Ba0.98Ce0.02SnF4.02-MM) exhibits the highest ionic conductivity and electrochemical stability. The conductivity (RT) exhibited by Ba0.98Ce0.02SnF4.02-MM is higher compared to earlier reports on different rare-earth ion-doped BaSnF4, which were primarily prepared by solution-based methods. Ion transport number measurement using dc polarization technique revealed that the conductivity exhibited by Ba0.98Ce0.02SnF4.02-MM is mainly due to ionic conduction. The observation of a higher ionic conductivity value in Ba0.98Ce0.02SnF4.02-MM highlights its great potential for use as a solid electrolyte in the fabrication of FIBs.

Conventional liquid electrolytes utilized in supercapacitors suffer from leakage, flammability, and poor adaptability making them unsuitable to design flexible, wearable, and portable devices. Despite the significant advancements in designing flexible electrode materials towards the fabrication of safer and integrated energy storage systems, the development of optically transparent and mechanically flexible polysaccharide-based solid-state electrolytes remains comparatively limited. Herein, we report a series of flexible solid-state electrolyte (FSSENaI-x; where x = 27, 43, 53, 60, 65, and 69 wt%) films, composed of konjac glucomannan (KGM), hydroxypropyl methylcellulose (HPMC), and sodium iodide (NaI). Among them, the FSSENaI-65 film exhibits optimal properties in terms of mechanical, optical, and ionic conductivity suitable for designing supercapacitor devices. It achieves a Young's modulus of ∼2.5 MPa with an exceptional elongation at break at 118%, along with an optical transparency of 88% at 800 nm. It delivers a high ionic conductivity of 2.77 mS cm−1 at room temperature and a wide electrochemical stability window of 2.4 V. A solid-state supercapacitor assembled with the FSSENaI-65 film shows a specific capacitance of 159 F g−1 at 1 A g−1, with an excellent cycling stability retaining 87.5% of its specific capacitance over 4000 cycles at 5 A g−1. It maintains a stable performance under bending conditions with a capacitance retention of 72.2% over 2000 cycles at 5 A g−1. The device furnishes a high energy density of 22.1 Wh kg−1 and power density of 500.6 W kg−1 at 1 A g−1 confirming its potential for next-generation flexible energy storage systems.

Abstract: This study explores the capabilities of solvothermally synthesized bismuth telluride (Bi2Te3) hexagonal platelets as a promising anode material for both Li-ion and Na-ion batteries. Bi2Te3 anode material exhibits a high initial discharge capacity of 837 mA h g−1 at a current density of 100 mA g−1 against Li metal whereas, an initial discharge capacity of 678 mA h g−1 is observed at a current density of 20 mA g−1 for the same against the Na metal. The Li- and Na-storage mechanism in Bi2Te3 platelets has been investigated by using both galvanostatic charge–discharge and cyclic voltammetry measurements. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy techniques have been used to examine the structural characteristics, surface morphology, and lattice vibrational modes of Bi2Te3 hexagonal platelets. Further, FTIR spectroscopy was employed to determine the presence of functional groups while X-ray photoelectron spectroscopy was employed for the elemental analysis of Bi2Te3 sample. Graphical abstract: (Figure presented.)

The escalating need for lithium-ion batteries (LIBs), driven by their expanding range of applications in our daily lives, has led to a surge in interest in metal selenides as potential anode materials. Among them, Bi2Se3 stands out as a promising anode material for LIBs due to its unique layered structure. Herein, we explored hexagonally structured layered Bi2Se3 platelets synthesized using the solvothermal method. The electrochemical performance of these platelets in LIBs was thoroughly examined, revealing an impressive initial discharge specific capacity of 556 mA h g−1 at a current density of 100 mA g−1 and a coulombic efficiency of 66.5%. Improved cycling stability, rate performance, and discharge voltage profile at various current densities were observed. The plateaus observed during the charge/discharge profile were clearly illustrated by the CV results. The reaction kinetics indicated that both ion diffusion and pseudo-capacitance behavior are crucial for the observed high electrochemical performance. Moreover, the hexagonal Bi2Se3 platelets exhibited a high ion-diffusion coefficient of 1.8 × 10−13 cm2 s−1 and a charge transfer impedance of 23 Ω post-cycling. Furthermore, the crystal structure, lattice vibrational bonding, and surface morphology of Bi2Se3 were explored using X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. FTIR spectroscopy was utilized for identifying the functional groups, while X-ray photoelectron spectroscopy (XPS) was used to identify the elemental composition and oxidation states of Bi2Se3.

Research studies on biomass-derived hard carbon are gaining notable scientific interest due to its potential application as a sustainable anode for Li-ion batteries (LIBs). The current study presents the development of hard carbon from soap-nut seed biomass, with the optimization of its pyrolysis temperature, followed by chemical activation using KOH- and ZnCl2-activated reagents. The physicochemical behaviour of the developed materials is studied by utilizing XRD, HRTEM, BET, and XPS techniques. CV and galvanostatic charge-discharge curves are examined to assess the potential of the material for the application as a sustainable anode in LIBs. The electrochemical performance of the developed materials obtained at various pyrolysis temperatures (600, 700, 800 and 900 °C) and chemically activated with KOH and ZnCl2 is explained with respect to their interplanar spacing, ID/IG ratio, and specific pore area. Among the different pyrolysis temperatures, the hard carbon pyrolyzed at 700 °C exhibits the maximum reversible specific discharge capacity of 391 mA h g−1 at a current density of 100 mA g−1. The present study also demonstrates that the electrochemical performance of the hard carbon deteriorates after chemical activation with ZnCl2, whereas chemical activation with KOH enhances its performance. The chemically-activated hard carbon using KOH exhibits a reversible specific discharge capacity of 454 mA h g−1 at 100 mA g−1 and delivers a better cycling stability (500 cycles) of 83 mA h g−1 at 300 mA g−1,.

Fluoride-ion batteries (FIBs) offer better theoretical energy densities and temperature stability, making them suitable alternatives to expensive Li-ion batteries. Major studies on FIBs operating at room temperature focus mainly on MSnF4 (M: Ba and Pb) solid electrolytes due to their favourable ionic conductivity values. PbSnF4 is the best fluoride ionic conductor known to date. However, it exhibits poor electrochemical stability. The present work demonstrates the development of TlSn2F5 through a single-step mechanical milling method. TlSn2F5 exhibits a better ionic conductivity value compared to the earlier reported various solid electrolytes, such as BaSnF4, KSn2F5, and La0.9Ba0.1F2.9, commonly considered for FIBs. Ionic transport number measurement using the dc polarization method indicates that TlSn2F5 is an ionic conductor. Furthermore, 19F NMR spectra measured at various temperatures demonstrate that the rise in conductivity with temperature is attributed to the rapid transport of fluoride ions. The present study indicates that TlSn2F5 can be utilized as a potential solid electrolyte for fabricating FIBs.

The development of all-solid-state Li-ion batteries (ASSLIBs) has gained significant attention due to their potential for improved safety, energy density, and performance compared to traditional Li-ion batteries. NASICON-type Li-ion conducting solid electrolytes (LICSEs) have emerged as a promising candidate for use in ASSLIBs because of their high Li-ion conductivity and excellent chemical stability. Replacement of the liquid electrolytes from conventional batteries with suitable solid electrolytes not only resolves some of their serious safety challenges, such as leakages and thermal instabilities, but also enhances their cycle life and power densities. One of the critical challenges in realizing all-solid-state batteries is not only the development of thermally and electrochemically stable solid electrolytes exhibiting good ionic conductivities but also reducing the impedance associated with the electrolyte-electrode interfaces in the device. NASICON-type solid electrolytes exhibit better stabilities compared to garnet-based systems, and they also exhibit better conductivity values in comparison to perovskite-based materials. This chapter shows the recent advances and challenges of NASICON-type LICSEs, LiM2(PO4)3 (M: Zr, Ti, and Ge), and their applications in all-solid-state batteries. Various strategies known to achieve solid electrolytes with improved ionic conductivity values by doping with dopants of different oxidation states-and further, the correlation of their transport results with respect to their crystal structure-are reviewed. The use of LiM2(PO4)3-based solid electrolytes in various polymer matrices for the advancement of composite-polymer electrolytes is underlined. Various synthesis methods known for the development of LiM2(PO4)3-based polycrystalline materials and composite-polymer electrolytes are summarized. We also provide an outlook for future research and development of NASICON-type LICSEs for use in ASSLIBs. Overall, this chapter highlights the potential of NASICON-type LICSEs as a key component for the development of high-performance ASSLIBs.

Biomass-derived hard carbon materials have received promising research interest because of their low cost, high abundance, and renewability. In the present study, high-performance hard carbon material is prepared from soap-nut seeds (SNS-0) using a simple pyrolysis process. Further, N (nitrogen) heteroatoms are introduced into the hard carbon matrix to modify its structure using melamine as the N source. High-resolution transmission electron microscopy images reveal the development of the localized graphite-like structure after the introduction of N atoms in the hard carbon, which are found to be beneficial for the storage and transport of the larger Na ions in the battery. The optimal doping of N (1:1 wt. ratio, SNS-1) in the hard carbon has improved the storage performance of the SNS-0 electrode, providing a reversible capacity of 353 mA h g−1 at a current density of 25 mA g−1. The improved electrochemical characteristics of the SNS-1 electrode over the other compositions are associated with its lesser specific surface area (282.87 m2 g−1) and higher interlayer spacing (0.38 nm). The present study not only reveals the useful conversion of a biomass waste, soap-nut seeds, into a low-cost and sustainable eco-friendly hard carbon material but also its potential use as an efficient anode for Na-ion battery applications.

Li-ion conducting solid electrolytes exhibiting NASICON structure have received promising research interest for their potential applications in safer all-solid-state Li-ion batteries. LiZr2(PO4)3 (LZP) belongs to the NASICON-type of materials exhibiting Li-ion conduction and furthermore offers lower interfacial resistance and good electrochemical stability against the Li-metal. LZP is known to crystallize in four polymorphs, namely monoclinic, orthorhombic, triclinic, and rhombohedral, and further, LZP crystallizing in rhombohedral structure is known to exhibit the highest ionic conductivity. The present work demonstrates the synthesis of LZP exhibiting rhombohedral structure at room temperature using the modified sol-gel method at a lower sintering temperature (900 °C). The effect of sintering temperature on the structural and transport behavior of LZP is studied by XRD, SEM, and impedance spectroscopy techniques. The complex impedance plots show the presence of two depressed semicircles associated with different capacitance values, indicating both bulk and grain boundary conductions. The bulk, grain boundary and total conductivity of LZP sintered at different temperatures are calculated. The bulk conductivity of LZP is found to increase with increase in the sintering temperature from 800 °C to 1100 °C, whereas LZP sintered at 900 °C exhibits the highest total conductivity value at room temperature, indicating the significant role of the grain boundary conductions in the total conductivity of LZP material. The transport results of LZP sintered at different temperatures are discussed with their unit cell volume (XRD), relative density (Archimedes method), and microstructure (SEM). Furthermore, the ionic transport number measurement by dc polarization shows that the major charge carriers are the ions and the electrochemical stability measurements by both cyclic voltammetry and linear sweep voltammetry show its stability with Li-metal is up to 5.1 V.

The present work shows the comparative studies on the magnetic properties of Ni0.4Zn0.6-xCoxFe2O4, (Ni–Zn–Co) and Ni0.4Zn0.6-xMnxFe2O4 (Ni–Zn–Mn) with x = 0.00 to 0.25 in steps of 0.05, ferrites synthesized by sol-gel autocombustion and conventional ceramic methods. Rietveld refinement data confirms the formation of single phase - spinel crystal structure in all the samples. The role of ferromagnetic dopants like Co and Mn on the structural, microstructural, magnetic characteristics such as Curie temperature (Tc), saturation magnetization and coercivity of NiZnFe2O4 ferrite are investigated. The influences of crystallite size obtained by using two different synthesis methods on different magnetic properties are highlighted. Continuous Tc increases have been noticed in both instances along with increasing dopant concentrations. However, compared to Ni–Zn–Mn ferrites, Ni–Zn–Co ferrites display greater Tc values. The experimental observed magnetic moments measured from vibrating sample magnetometer (VSM) are fitted with the theoretical data. The saturation magnetization values exhibit a marginal increase in the bulk form of the material as compared to its nanocrystalline counterparts. On the basis of distribution of cation and exchange interactions between magnetic cations at its tetrahedral and octahedral sublattices, the typical mechanisms accountable for the observed trends were elucidated. In addition, the dc-resistivity and dielectric loss are measured to show the application aspects of the materials in various potential device applications.

The search for obtaining a Co free low-cost and high-capacity anode thin film material for high energy density all-solid thin film batteries has been driving the increasing innovation and research in Li-ion battery (LIB) technology. In the present case, LiFe5O8 (LFO) thin films are prepared by pulsed laser deposition (PLD) technique and their electrochemical properties, Li ion dynamics, conducting processes at various frequencies and current rates are explored. LFO thin films are seen to crystallize in ordered α -phase with an inverse spinel structure. Chemical state of all the elements is analysed using X-ray photoelectron spectroscopy method. Cyclic voltammeter (CV) study carried out between 0–3 V shows the reduction peak at 0.76 V initially and in the later cycles at 0.86 V with a small shift depicting the exact conversion type behaviour of the LFO thin film. LFO thin film exhibits specific discharge capacity of 25 μAh/cm2 at 10 μA/cm2 current density during the first cycle. Rate capability measurements are carried out at various current densities of 10, 20, 30, 40, 50 and 10 μA/cm2. Li-ion diffusion coefficient during the de-lithiation and lithiation process is seen to be 3.78 × 10−14 cm2/s and 1.41 × 10−13 cm2/s, respectively. CV studies at various scan rates indicates that the mechanism of Li+ storage is dominated by a diffusion-controlled process at low scan rates and with increasing scan rate it becomes a surface-controlled process. Electrochemical impedance studies at various frequencies shows the decrease in charge transfer resistance with increasing cycles. Combined structural, chemical, electrochemical and impedance studies of LFO thin films indicates that these films can be employed for fabricating Co and Ni free all-solid thin film Li-ion batteries for energy storage applications.

Investigations on SnF2-based solid electrolytes are gaining significant scientific attention because of their promising applications as solid electrolytes for all-solid-state fluoride ion batteries (FIBs) operating at room temperature. FIBs are potential alternatives for expensive Li-ion batteries with toxic and flammable liquid electrolytes. SrSnF4 belongs to the MSnF4 (M: Pb, Ba, and Sr)-type materials exhibiting a layered structure. Here, we present the structural and transport characteristics of two polymorphs of SrSnF4 using X-ray diffraction and impedance spectroscopy techniques. SrSnF4 crystallizing in a cubic fluorite structure is obtained just by mechanical milling the powder samples of SrF2 and SnF2 taken in a 1:1 ratio for 10 h, whereas annealing the milled powder at 623 K in the N2 atmosphere transforms SrSnF4 from its cubic phase to the stable tetragonal structure. The structural details of both the cubic and tetragonal SrSnF4 have been obtained by performing the Rietveld refinement. The resultant phase change after soft annealing enhances the room-temperature conductivity value from 2.05 × 10-6 S/cm for the cubic phase to 1.16 × 10-5 S/cm for the tetragonal phase. The transport number measurement by the dc polarization technique with the cell of configuration Ag/SrSnF4/Ag reveals that the conductivity is due to the ions. The frequency response of conductivity data is analyzed using the Almond-West formalism to find their hopping frequency and mobile carrier concentration factor at different temperatures. The scaling of the frequency-dependent conductivity spectra shows that the relaxation behavior of the mobile ions is temperature independent.

Na3Zr2Si2PO12 (NZSP)-based materials are promising solid electrolytes for all-solid-state-Na-ion batteries (ASSNIBs) because of their wide electrochemical stabilities and good ionic conductivities at room temperature. The major challenges in developing NZSP-based materials include the occurrence of unexpected secondary phases that often limits their ionic conductivity values. In addition, the development of these materials often needs higher sintering temperatures (> 1100 °C) that may lead to the minor loss of Na during the preparation. The Na content in NZSP is often increased to minimize the loss of Na during preparation and furthermore to enhance its concentrations in NZSP. The transport behaviour of NZSP material is often controlled by the stoichiometries of different elements present. In the current work, Na-excess NZSP materials are prepared by solid-state reaction using different types of Na-precursors such as Na2CO3, Na3PO4·12H2O, Na2SiO3, and NaF as an excess Na-source keeping its Na-stoichiometry same. However, the selection of the precursors changes stoichiometries of the other elements like Si, P, and O present in NZSP. The formations of the Na-excess NZSP materials exhibiting monoclinic NZSP structure are confirmed by X-ray diffraction. The conductivity results measured by impedance spectroscopy are explained with respect to their unit cell volume, density, and bottleneck area available for the Na-ion diffusion. Na-excess NZSP material using Na2CO3 (Na3.45Zr2Si2PO12.22, NC) as an excess Na-source, sintered at 1200 °C, exhibited highest ionic conductivity. The ionic transport number measurement by the dc polarization technique confirms the ionic nature of the principal charge carriers. Furthermore, the linear sweep voltammetry measurement shows its electrochemical stability window is up to 5.2 V implying the suitability of the Na3.45Zr2Si2PO12.22 material as a potential solid electrolyte for ASSNIBs.

Recent reports on fluoride ion batteries (FIBs) show its promising credentials as suitable alternatives for Li-ion batteries suffering with issues like high cost, limited source, and safety. Unlike to the other alternative battery technologies such as Na, FIBs are in the early stage of progress. Development of solid electrolytes with fast fluoride ion transport is one of the major challenges in FIBs. NH4Sn2F5 belongs to the SnF2 based MSn2F5 (M: K, Rb, and NH4) solid electrolytes exhibiting two-dimensional F ion conduction. The present work reports the structural and transport details of mechanochemically synthesized NH4Sn2F5, where the material is prepared just by milling the initial SnF2 and NH4F powders (2:1) for 10 h without any heat treatment. The formation of the material exhibiting monoclinic structure at room temperature (RT) is confirmed by X-ray diffraction followed by the Rietveld refinement. The temperature dependent conductivity results at different temperature regions are explained with respect to its structural transformations, which is furthermore correlated with the differential scanning calorimetry observation. Later the conductivity values at different temperatures of mechanochemically prepared NH4Sn2F5 are compared with the earlier reported MSn2F5 (M: Na and K) materials synthesized by the same method and the results are explained with respective to their crystal structure. The current study shows that the presence of the larger NH4 cation in MSn2F5 (M: Na, K, NH4) systems causes fast transport of F ions resulting in the highest fluoride ionic (anionic) conductivity value. Like BaSnF4, the solid electrolyte which is often used by many research groups for different FIBs operating at RT, mechanochemically synthesized NH4Sn2F5 has a great potential to be tested as a solid electrolyte in both conversion type and intercalation type FIBs because of its higher RT conductivity value arising from the motion of F ions.

Research studies on Na-ion batteries (NIBs) are receiving significant scientific and commercial attention recently owing to the availability of low-cost, safe, and abundant materials in comparison to the conventional Li-ion batteries. The cathode material in a battery plays a crucial role in determining its cell capacity and cycle life. NASICON-based Na3V2(PO4)3, NVP, is known to be a favorable cathode material for NIBs due to its structural stability with high Na-ion mobility. The present work shows the structural and electrochemical properties of bare NVP/C and NVP/C partially doped with low-cost and much abundant transition element Fe/Mn at the toxic and expensive V site. The bare NVP/C as well as the transition-metal ion-doped NVP/C materials are prepared by the sol-gel method. XRD and FTIR studies confirm the formation of materials exhibiting the rhombohedral NVP structure (R3¯ c) without any trace of impurities. The presence of a carbon layer in the investigated cathode materials is confirmed by the HRTEM micrographs; furthermore, the oxidation states of different transition-metal elements present are evaluated by X-ray photoelectron spectroscopy. Electrochemical studies reveal that the moderate doping of Fe/Mn in NVP/C results in an enhancement in discharge capacities in the doped materials at different C rates compared to the bare NVP/C sample. The differences in their electrochemical results are explained with respect to their Na-ion diffusion coefficient values obtained using the Randles-Sevcik equation. A Mn-doped NVP/C material exhibits an enhanced discharge capacity of 107 mA h g-1at 0.1C with 90% capacity retention even after 100 cycles at 1C current rate. At the end, a Na-ion full cell (NVMP/C||HC) comprising a Mn-doped NVP/C cathode with the commercial hard carbon anode delivering a discharge capacity of 90 mA h g-1is demonstrated.

Na3Zr2Si2PO12 is a well-known solid electrolyte because of its potential applications in Na-ion batteries and gas sensors. In this work, the structural and transport properties of Na3Zr2Si2PO12 synthesized by solid-state reaction and sol–gel techniques are compared. In both methods, a monoclinic phase for Na3Zr2Si2PO12 is confirmed by X-ray Diffraction and FTIR spectroscopy techniques. The impedance measurements show higher conductivity in Na3Zr2Si2PO12 prepared by solid-state reaction. The role of sintering temperatures on the transport results of Na3Zr2Si2PO12 has been investigated. The temperature dependent conductivity plots of Na3Zr2Si2PO12 show a change in the slope at 163 °C corresponding to its structural phase transition from monoclinic to rhombohedral form, which is further supported by its DSC result. Furthermore, the role of excess Na on the ionic conductivity of Na3Zr2Si2PO12 using two different Na precursors Na2CO3 and Na3PO4 keeping same Na-stoichiometry has been investigated.

LaF3 based fast ion conducting materials are well-known potential solid electrolytes for applications in different solid-state ionic devices like fluoride ion batteries. LaF3 of crystallite size in the nanometer range is obtained by mechanical milling the as procured LaF3 for a few hours. The mechanically milled LaF3 shows higher conductivity in comparison to its un-milled forms. The enhanced conductivity value exhibited by the mechanically milled LaF3 is explained with respect to its smaller crystallite size and induced micro-strain during the milling process. The influence of bivalent dopant, BaF2 (fluorite structure) on LaF3 (tysonite structure) has been studied using XRD and impedance spectroscopy techniques. La0.9Ba0.1F2.9 shows higher conductivity in comparison to LaF3 conductivity and the observed result is explained with respect to the differences in the ionic radii and valence state of the dopant Ba2+ and the host La3+ ions. Furthermore, the role of the co-dopant CaF2 on the structural and transport properties of BaF2 doped LaF3 keeping same La and F stoichiometry as in La0.9Ba0.1F2.9 is investigated. The transport results indicate a lower conductivity value in La0.9Ba0.05Ca0.05F2.9 in comparison to La0.9Ba0.1F2.9 conductivity.

Na3Zr2Si2PO12 based solid electrolytes are well known materials because of their potential applications in different solid-state ionic devices. This review article presents the structural and transport results of Na3Zr2Si2PO12 based solid electrolytes prepared by different dry and wet methods known in the literature. The advantages and limitations of different synthesis methodologies to achieve the phase pure, high dense Na3Zr2Si2PO12 based materials are presented. The influence of the valence state, ionic radii of aliovalent dopants on the ionic conductivity of Na3Zr2Si2PO12 have been discussed with respect to their crystal structure. The role of sintering temperature, sintering durations, and sintering agents on the phase purity, density, and conductivity of Na3Zr2Si2PO12 based solid electrolytes are reviewed. Besides Na3Zr2Si2PO12 based polycrystalline solid electrolytes, the transport results of Na3Zr2Si2PO12 based grain boundary free glasses and flexible polymer electrolytes are also discussed. The applications of Na3Zr2Si2PO12 based solid electrolytes in different electrochemical devices are outlined.

In this work, a novel memory capacitor structure has been presented with AlOx/Al2O3 bilayer dielectrics on high mobility Epitaxial-GaAs substrate. We have demonstrated the chemical and electrical properties of metal–electrode/AlOx/Al2O3/epi-GaAs-based memory device in detail. Sputter-grown non-stoichiometric AlOx has been used for both the charge trapping layer and blocking layer due to its intrinsic charge trapping capability and high bandgap. Ultra-thin tunneling layer of thicknesses 5 nm and 15 nm were prepared by atomic layer deposition technique and memory properties were compared on promising high mobility Epitaxial-GaAs/Ge heterostructure. The proposed device shows excellent charge trapping properties with a maximum memory window of 3.2 V at sweep voltage of ± 5 V, with good endurance and data retention properties. Oxygen-deficient AlOx layer acted as a charge trapping layer without any additional blocking layer which is impressive for non-volatile memory application on high mobility epi-GaAs substrate. In addition, density Functional Theory (DFT) has been employed to understand the physical origin of the intrinsic charge trapping defects in AlOx dielectric layer.

This review article presents the use of mechanical milling technique for the synthesis of a variety of fast fluoride ion conducting materials for different electrochemical device applications. The influence of various milling parameters such as milling time, type of the milling pot, and rotation speed on the structural and transport parameters of different fluoride-based materials is reviewed. The advantages and disadvantages of the milling technique in comparison to the other methods are outlined. The ionic conductivity values of different fast fluoride ion conducting materials prepared by various synthesis routes are compared. At the end, it is observed that mechanical milling is an easy and promising method for the synthesis of different fast fluoride ion conducting materials in comparison to the same by other methods and furthermore, their ionic transport results indicate an enhancement in conductivity values by two to four orders in the mechanochemically synthesized materials. [Figure not available: see fulltext.]

We report on band edge parameters calculated from the electrochemical data, work function, Li ion dynamics and excellent electrochemical properties of Li4Ti5O12 thin films prepared by RF sputtering technique. Raman spectra recorded at room temperature confirms the formation of Li4Ti5O12 thin films in spinel structure. Surface morphology and roughness values are analyzed using scanning electron microscope (FESEM) and atomic force microscope (AFM) images. The average work function value at room temperature is seen to be 5.2 eV. Cyclic voltammetry studies confirm the oxidation and reduction peaks appear at 1.58 V and 1.55 V respectively. Band edge parameters are calculated from the electrochemical data and band diagram for the Li4Ti5O12 thin film is established. Li ion dynamics is evaluated using electrochemical impedance spectroscopy data analyzed with equivalent circuit model. Conductivity values of Li4Ti5O12 thin films before and after the redox process is seen to be 1.25 × 10−6 and 1.36 × 10−6 S/cm respectively. Correlation between the surface properties, band edge parameters and the electrochemical process is established and the band diagram of Li4Ti5O12 thin film is proposed.

This paper describes nonlinear ion transport properties of liquid and solid electrolytes. Typically, the relation between ionic current density and electric field becomes nonlinear at electric fields above 50–100 kV/cm. We review the 1st and 2nd Wien effect found in classical strong and weak electrolyte solutions as well as the strong nonlinear ion transport effects observed for inorganic glasses and for polymer electrolytes. Furthermore, we give an overview over models describing nonlinear ion transport in electrolyte solutions, in glasses and in polymers. Recent results are presented for the nonlinear ionic conductivity of supercooled ionic liquids. We show that supercooled ionic liquids exhibit anomalous Wien effects, which are clearly distinct from the classical Wien effects. We also discuss the frequency dependence of higher-order conductivity and permittivity spectra of these liquids.

We have measured the third-order permittivity spectra ε3 3 of a monocationic and of a dicationic liquid close to the glass transition temperature by applying ac electric fields with large amplitudes up to 180 kV/cm. A peak (“hump”) in the modulus of ε3 3 is observed for a mono-cationic liquid after subtraction of the dc contribution from the imaginary part of ε3 3. We show that the origin of this experimental “hump” is a peak in the imaginary part of ε3 3, with the peak height strongly increasing with decreasing temperature. Overall, the spectral shape of the third-order permittivity of both ionic liquids is similar to the predictions of a symmetric double well potential model, although this model does not predict a “hump” in the modulus. In contrast, an asymmetric double well potential model predicts a “hump,” but the spectral shape of both the real and imaginary part of ε3 3 deviates significantly from the experimental spectra. These results show that not only the modulus of ε3 3 but also its phase is an important quantity when comparing experimental results with theoretical predictions.

The temperature dependence of magnetization, anisotropy, ac and dc conductivity of CoFe2-xSnxO4 (x = 0.025, 0.05, 0.075) were investigated and the results are reported. All the compounds were prepared by a solid-state reaction, and the formation of the compounds in the cubic inverse spinel phase was confirmed from their Rietveld refined x-ray diffraction (XRD) patterns and Raman spectra. Increments in the lattice constant were observed upon the partial substitution of Fe3+ by Sn4+. The presence of all elements and their ionic states were confirmed from x-ray photoelectron spectroscopic studies. Magnetic hysteresis loops were measured for each compound at temperature 20 K and 50-300 K (in steps of 50 K) using a superconducting quantum interference device vibrating sample magnetometer. Both magnetization and magnetic anisotropy showed a decrease in values with increasing Sn substitution. Room temperature (RT) magnetization is seen to decrease from 80-65.91 emu g-1 with increasing Sn concentration from x = 0 (CoFe2O4) to 0.075 (CoFe1.925Sn0.075O4). The high field regimes of the hysteresis loops were modeled using the law of approach to the saturation magnetization equation. The temperature variation of magnetization and magnetic anisotropy are explained on the basis of a one-ion model. Complex impedance spectroscopy studies at RT show that the conductivity in these materials is predominantly due to the intrinsic bulk grains. With increasing the temperature, evolution of the grain boundary conduction is clearly seen through the appearance of a second semi-circle in the complex impedance plots. The RT total dc conductivity value of CoFe2-xSnxO4 (x = 0, 0.025, 0.05, 0.075) is found to be 5.78 × 10-8, 8.56 × 10-8, 1.44 × 10-7 and 1.11 × 10-7 S cm-1 respectively. The observation of well-distinguishable grain and grain boundary conductions and the low conductivity values in the CoFe2-xSnxO4 (x = 0, 0.025) materials indicates that these materials are promising candidates for high-frequency applications.

We have measured conductivity spectra of several supercooled monocationic and dicationic ionic liquids in the nonlinear regime by applying ac electric fields with large amplitudes up to about 180 kV/cm. Thereby, higher harmonic ac currents up to the 7th order were detected. Our results point to the existence of anomalous Wien effects in supercooled ionic liquids. Most ionic liquids studied here exhibit a conductivity-viscosity relation, which is close to the predictions of the Nernst-Einstein and Stokes-Einstein equations, as observed for classical strong electrolytes like KCl. These "strong" ionic liquids show a much stronger nonlinearity of the conductivity than classical strong electrolytes. On the other hand, the conductivity-viscosity relation of the ionic liquid [P6,6,6,14][Cl] points to ion association effects. This "weak" ionic liquid shows a strength of the nonlinear effect, which is comparable to classical weak electrolytes. However, the nonlinearity increases quadratically with the field. We suggest that a theory for explaining these anomalies will have to go beyond the level of Coulomb lattice gas models.

Enhanced ferromagnetic properties and high temperature dielectric anomalies in the temperature range of 300-873 K in Bi0.9Ca0.05Sm0.05FeO3 (BCSFO) prepared by hydrothermal method are reported. BiFeO3 is seen to crystallize in rhombohedrally distorted perovskite structure without any impurity phase. Substitution of small amount of Ca and Sm (Bi0.9Ca0.05Sm0.05FeO3) leads to increase in the lattice constant values and formation of small amount of secondary phase. Magnetization curve of pure BFO indicates very weak ferromagnetism combined with antiferromagnetic nature of the samples. Whereas, BCSFO sample shows very clear and enhanced ferromagnetic nature. Saturation magnetization and Neel's temperature values are found to be 4.36 emu/g and 664 K, respectively. X-ray photoelectron spectroscopy indicates the creation of oxygen vacancies upon Ca substitution in Bi site. Dielectric anomalies at 420 and 540 K were observed for Bi0.9Ca0.05Sm0.05FeO3 from the temperature variation of dielectric constant and specific heat capacity measurements. Observation of dielectric anomalies in pure BiFeO3 sample reveals that the origin of dielectric peaks is purely from the primary phase. Raman spectroscopy study indicates a clear shift and broadening of A modes (between 100 and 200 cm-1) at the dielectric anomaly temperatures supporting the observed dielectric anomalies.

We have carried out nonlinear ion conductivity measurements on the supercooled ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide[C6mim][NTf2] by applying ac electric fields with amplitudes up to about 200 kV/cm. At these field amplitudes, 3ω and 5ω harmonic components in the current response were detected, and the higher-order conductivity coefficients σ 3 1, σ 3 3, σ 5 3, and σ 5 5 were determined. The frequency and temperature dependence of these conductivity coefficients was analyzed in detail. The most important findings were the following: (i) The third-order spectra σ 3 1 and σ 3 3 exhibit very similar values in the dc plateau regime but differ considerably in the dispersive regime. The same was observed for the fifth order spectra σ 5 3 and σ 5 5. (ii) In the dispersive regime, the third-order spectra display a minimum, while the fifth-order spectra display a maximum. (iii) The frequencies of these minima and maxima are thermally activated with the same activation energy as the low-field dc conductivity σ1,dc, whereas the dc values of the higher-order conductivity coefficients, σ3,dc and σ5,dc, are characterized by lower activation energies.

We report on the structural, temperature, and frequency dependent impedance studies of Ti doped cobalt ferrite material (CoFe<inf>1.95</inf>Ti<inf>0.05</inf>O<inf>4</inf>) in comparison with the pure CoFe<inf>2</inf>O<inf>4</inf>. XRD and Raman spectroscopy studies confirm the inverse spinel crystallization of the materials with space group of Fd-3 m. Scanning electron microscope images shows the microcrystalline nature of the particles. Homogeneity, stoichiometry, and ionic states of the ions in the composition were confirmed by energy dispersive X-ray analysis and X-ray photoelectron spectroscopic studies. Temperature and frequency dependent real (Z′) and imaginary (Z″) part of the impedance shows the existence of relaxation processes and their distribution in CoFe<inf>2</inf>O<inf>4</inf> and CoFe<inf>1.95</inf>Ti<inf>0.05</inf>O<inf>4</inf> materials. Complex impedance spectroscopy studies at low temperatures shows that the conductivity in these materials is predominantly due to the intrinsic bulk grains. With increasing the temperature, evolution of grain boundary conduction is clearly seen through the appearance of a second semi-circle in the complex impedance plots. Room temperature total dc conductivity of both CoFe<inf>2</inf>O<inf>4</inf> and CoFe<inf>1.95</inf>Ti<inf>0.05</inf>O<inf>4</inf> materials is found to be 5.78 × 10^-8 and 1.61 × 10^-7 S/cm, respectively. Temperature variation of dc electrical conductivity follows the Arrhenius relationship and the activation energies for CoFe<inf>2</inf>O<inf>4</inf> corresponding to grain (0.55 eV for CoFe<inf>2</inf>O<inf>4</inf>), grain boundary (0.52 eV), and total conduction (0.54 eV) are discussed. Observation of well distinguishable grain and grain boundary conductions and the low conductivity values in CoFe<inf>2</inf>O<inf>4</inf> and CoFe<inf>1.95</inf>Ti<inf>0.05</inf>O<inf>4</inf> materials indicates that these materials are promising candidates for the high frequency applications.

This article presents the structural and transport characteristics of hydrothermally synthesized LaF3 nanoparticles with an average crystallite size of 35nm. The phase formation of the material is confirmed by both X-ray diffraction and transmission electron microscopy techniques. In addition, phase purity of the LaF3 nanoparticles is corroborated by micro-Raman spectroscopy studies. The complex impedance plots at different temperatures reveal that the conductivity is predominantly due to the intrinsic bulk grains and the conductivity relaxation is non-Debye in nature. The frequency variation of conductivity exhibits dispersion at higher frequencies that can be explained with the frame work of Almond-West formalism. The conduction process is controlled by the mobility of the charge carriers and the charge of transport of mobile fluoride ions occur through hopping mechanism. The scaling behavior of both frequency dependence of conductivity and complex impedance plots at different temperatures confirm that the relaxation mechanism of the mobile fluoride ions is independent of temperature.

SrRuO3, a p-type metallic conductor with a small thermopower, and SrTiO3, a p-type insulator with a large thermopower in its hyperstoichiometric state, have been reported to make a complete solid solution. It is, thus, suggested that the thermoelectric power factor, conductivity times thermopower squared (σθ2), may be best optimized by mixing these two extreme oxides. In order to explore this possibility, we examined σ and θ of the solution Sr(Ru1-xTix)O3 against composition (0 ≤ x ≤ 1), temperature (300 ≤ T/K < 1000) and oxygen activity (-4≤logaO2<0), and subsequently its crystallographic structure against x at room temperature. It has been found that, contrary to literature, there falls a miscibility gap over the composition range 0.1 < x < 0.6. While there occurs a metal-to-insulator transition crossing the miscibility gap, θ remains little dependent on T and aO2 for the compositions up to x = 0.9. Unexpectedly, however, θ changes its sign twice with increasing x, indicating the majority carrier type changes from p to n at a composition in 0.6 < x < 0.9 and back to p at a composition in 0.9 < x < 1.0, whereas σ decreases monotonically. The highest power factor is observed, contrary to the expectation, at x = 0 (pure SrRuO3) on the order of 10-4 W/mK2. The origin of the repeated carrier-type changes is discussed in terms of electronic-structure change. © 2014 American Physical Society.

Investigation on the X-ray diffraction results of rare earth ions such as Eu3+ and Nd3+ doped BaSnF4 materials indicates that the doped materials show a similar pattern of BaSnF4 with the same tetragonal structure (P4/nmm). The transport properties of the materials have been investigated by impedance spectroscopy, and the results show that the conductivity values are closely related to both concentration and type of the dopant ion. All of these doped materials show an increase in conductivity over un-doped BaSnF4. The highest conductivity is observed in 3 mol% Nd3+ ion-doped BaSnF4 system (9.01 × 10-4 Scm-1), which is about one order higher in comparison to BaSnF4 conductivity (1.1 × 10-4 Scm-1). The room temperature emission spectrum of BaSnF4:Eu3+ and BaSnF4:Nd3+ shows the characteristic bands arising from 5D0 → 7Fj (j = 1, 2, 3, and 4) and 4F3/2 to 4Ij (j = 9/2 and 11/2) transitions of Eu3+ and Nd3+ ions, respectively. © 2013 Springer-Verlag Berlin Heidelberg.

This article presents the results on the growth and characterization of BaSnF4 thin films on glass substrates prepared by pulsed laser deposition technique. The structural results of BaSnF4 thin film carried out by glancing angle X-ray diffraction technique indicates the formation of the film with similar structure (tetragonal, P4/nmm) to the bulk target material. The absorption coefficient and band gap of the film is determined by suitable analysis of the transmittance spectra. The transport properties of the thin films are studied using impedance spectroscopy in the temperature range of 323-573 K. The frequency-dependent imaginary part of impedance plot shows that the conductivity relaxation is non-Debye in nature. The scaling behavior of the imaginary part of impedance at various frequencies indicates temperature-independent relaxation behavior. © 2013 Springer-Verlag Berlin Heidelberg.

We report on the structure, DC electrical conductivity, dielectric, and impedance spectroscopic characterization of microcrystalline LiFePO4 cathode material. Frequency variation of the dielectric constant (ε′) exhibits the dispersion that can be modeled with a modified Debye's function, which considers the possibility of more than one ion contributing to the relaxation. At a constant frequency, the dielectric constant value increases with increasing temperature. At 100 kHz, the measured values of ε′ at 433 and 473 K are 4.6 and 5.7, respectively. The real (Z′) and imaginary part (Z″) of impedance as a function of frequency at different temperatures indicate the existence of relaxation processes and their distribution in LiFePO4. Cole-Cole plots at different temperatures indicate that the conductivity is predominantly due to the intrinsic bulk grains. Temperature variation of DC electrical conductivity (σ dc) (273-573 K) follows the Arrhenius relationship. Activation energy (E a) calculated from the ln σ dc versus 1000/T plot is 0.44 eV, which indicates the predominant electronic conduction mechanism in LiFePO4. The AC conductivity increases with increasing frequency and temperature. © 2013 Springer Science+Business Media New York.

This review article presents a brief overview of synthesis and application aspects of fast fluoride ion conducting materials in the field of Solid State Ionics. Possible synthesis methodologies known in the literature for the preparation of various fluoride materials have been outlined. Further, their transport characteristics with respect to their crystal structure have been discussed. Various approaches influencing their ionic conductivity value in the light of synthesis methodology, composition, dopant concentration, crystallite size, microstructure etc. have been reviewed. At the end, possible technological applications of fast fluoride ion conducting materials in different solid state ionic devices have been presented. © 2013 Elsevier B.V.

The composite solid electrolytes, NaSn2F5, dispersed with submicron size Al2O3 fillers of various concentrations and particle sizes have been synthesized through mechanochemical milling technique. X-ray diffraction and microstructure results indicate the biphasic nature of the composite materials. The transport properties of the present composite materials have been investigated by means of impedance spectroscopy, and the results show that the improvement in conductivity increases with decrease in the particle size of the filler. An enhancement in conductivity of two orders in magnitude is obtained for NaSn2F5 with Al2O3 dopant concentration of 10 mol%. The activation energy responsible for conductivity relaxation, calculated from the modulus spectra, is found to be almost the same as the value obtained from temperature variation of dc conductivity. The scaling result of the imaginary part of the modulus shows the temperature-independent relaxation behavior. © 2012 Springer-Verlag.

The ionic conductivity of Sn (1-x)K xF (2-x) systems has been investigated as a function of composition and temperature using complex impedance spectroscopy. These materials have been prepared by normal solid state reaction method and characterized through XRD and DSC. The highest conducting sample has been prepared through mechanochemical synthesis technique in addition to solid state reaction method. The universal scaling behavior of the real and imaginary part of the impedance including complex impedance plots indicating temperature independent relaxation behavior has been demonstrated. This result is further supported by the scaling behavior of the real part of the conductivity. © 2012 Elsevier Ltd.

SnF 2 of various crystallite sizes have been obtained by mechanical milling. Further, the crystallite size dependent conduction characteristics of SnF 2 have been investigated by X-Ray Diffraction, High Resolution Scanning Electron Microscopy and Impedance Spectroscopy techniques. The crystallite size and microstrain developed during the milling process have been calculated by using Scherrer's semi-empirical formula. Further, an attempt is made to correlate the conductivity results of mechanically milled samples with the crystallite size and microstrain. In all cases, the temperature dependent conductivity plot obeys the Arrhenius behavior. The enhancement in conductivity of SnF 2 is found to be of two orders of magnitude after simply milling for 10 h. © 2012 Elsevier B.V. All rights reserved.

The high performance fluoride ion conductor BaSnF4 has been prepared by a simple precipitation in addition to both solid state reaction and mechanochemical synthesis techniques. XRD results indicate that the material BaSnF4 obtained by all the methods crystallizes with the same tetragonal structure (P4/nmm). The crystallite size and morphology of the BaSnF4 particles determined by XRD and FE-SEM show a variation with respect to different methods of preparation. The transport properties of BaSnF4 have been investigated by impedance spectroscopy and the results show that the conductivity values are closely related to the crystallite size and micro-strain. The transport number measurement and NMR studies further confirm that the increase in conductivity is due to fluoride ions. The scaling result of complex impedance plots shows that the dynamical process occurring at various frequencies are independent of temperature. © 2011 Elsevier Ltd. All rights reserved.

The conduction characteristics of SnF2 from room temperature (300 K) to 463 K have been investigated by using impedance spectroscopy. The temperature dependent conductivity plot shows a break in conductivity around 443 K corresponding to the α → γ phase transition temperature. The electrical properties of SnF2 are also investigated by extracting dielectric and modulus data from impedance values. The frequency dependent plots of M″ and Z″ show that the conductivity relaxation is non-Debye in nature. The activation energy responsible for relaxation has been calculated from the modulus spectra and is found to be almost the same as that from the temperature dependent dc conductivity data. The real part of conductivity and permittivity in addition to the modulus spectra of the present system show scaling behavior, which means σ′(ω), ε′(ω) and M′(ω) isotherms successfully collapse to a single master curve indicating that the relaxation mechanism is temperature independent. Different scaling approaches have been applied to arrive at a correlation between the scaling parameters. © 2009 Elsevier B.V. All rights reserved.

Sodium pentafluorodistannite has been synthesized through high-energy ball milling as well as by solid-state reaction method and characterized through XRD and DSC techniques. The electrical conductivity and modulus characteristics of the system are investigated in the temperature range from 373 K to 473 K by means of impedance spectroscopy. The conductivity of the ball-milled sample is about one order of magnitude higher compared to the sample prepared by solid-state reaction method. The frequency dependent conductivity of the present system shows the power law feature. The real part of dielectric permittivity shows a huge value at lower frequencies due to the presence of space charge polarization. The activation energy responsible for relaxation calculated from the modulus spectra is found to be almost the same as the value obtained from temperature variation of dc conductivity. The conductivity and modulus spectra of the present system show scaling behavior, which means that σ*(ω) and M″(ω) isotherms successfully collapse to a single master curve indicating temperature independent relaxation behavior. © 2009 Elsevier B.V. All rights reserved.