Impedance spectroscopy measurements evidence superionic Li+ mobility (>10−3 S cm−1) at room temperature and fast ionic mobility for Na+ (5 × 10−6 S cm−1) in high entropy oxides, a new family of oxide-based materials with the general formula (MgCoNiCuZn)1−x−yGayAxO (with A = Li, Na, K). Structural investigations indicate that the conduction path probably involves oxygen vacancies.

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Room temperature lithium superionic conductivity in high entropy oxides

Nasicons (sodium super ion conductors) are a class of solid electrolytes. Their structure, compositional diversity, evolution, and applications are reviewed. A wide range of materials is considered based on crystalline and glassy Nasicon compositions.

A wide-ranging review on Nasicon type materials

Ionic conductivity for the chitosan-NH 4 CF 3 SO 3 system was conducted over a wide range of frequency and at temperatures between 298 and 313 K. Dielectric data were analyzed using complex permittivity e * and complex electrical modulus M * for the sample with the highest ionic conductivity at various temperatures. The temperature-dependent conductivity data obeys Arrhenius relationship. Jonschers universal power law was used to analyze AC conductivity of the sample. Hopping frequency was determined and activation energy of hopping is almost equal to the activation energy of conduction. The AC conductivity master curve was obtained for the highest conducting sample when scaled vertically by σ DC and horizontally by ω P .

Conductivity studies of a chitosan-based polymer electrolyte

Correlation between micro-structural properties and ionic conductivity of Li1.5Al0.5Ge1.5(PO4)3 ceramics

Ion transport in sodium ion conducting solid electrolytes

Different NASICON systems with general formula Am Bn P3O12 were prepared by melt quenching method, where A � /Na, and B� /Cu, Al, Fe, FeCd. The prepared compounds were characterized by X-ray diffraction, and Fourier transform infrared spectroscopy. The electrical conductivity measurements were made on the different NASICON materials as a function of frequency (20 Hz to 1 MHz) at different temperatures. The bulk conductivity was obtained from the impedance analysis. The dc conductivity activation energies are found to be in the range 0.40 � /1.53 eV. The conductivity and dielectric spectra show the power low feature. The framework of the Almond � /West conductivity formalism is applied to discuss the ac conductivity and determined the dc conductivity sdc, hopping frequency vp, and dimensionless frequency exponent n . The conductivity master curves for the conductivity spectra are obtained by scaling the frequency by (i) vp and (ii) sdcT , where T is temperature in Kelvin. Both types of scaling show same conductivity master curves. # 2002 Published by Elsevier Science B.V.

Ac conductivity, dielectric studies and conductivity scaling of NASICON materials

Lithium and potassium ion conduction in A3TiB′P3O12 (A=Li, K; B′=Zn, Cd) NASICON-type glasses

Vitreous phases of K3M2P3O12 (M = B, Al, Bi) NASICON-type materials are prepared and their electrical properties are investigated over a frequency range from 42 Hz to 1 MHz and at different temperatures. An anomalous diffusion model (ADM) is applied to discuss the ac conductivity, permittivity and electric modulus of the NASICON-type glasses. The ADM is used to extract the dc conductivity and relevant physical parameters, namely, crossover length and relaxation frequency in the ion diffusion process. The dc conductivities and relaxation frequencies are thermally activated, with activation energies found to be in the range 0.70–0.82 eV. The frequency- and temperature-dependent conductivity spectra of individual glasses can be superimposed by means of the Summerfield scaling. © 2005 Elsevier B.V. All rights reserved.

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Vitrification of K3M2P3O12 (M = B, Al, Bi) NASICON-type materials and electrical relaxation studies

Vitreous M4AlCdP3O12 (M = Li, Na, K) NASICON-type materials are synthesized, characterized and their electrical properties are reported at different temperatures in the frequency range of 42 Hz to 1 MHz. Ac conductivity and permittivity data are analyzed by using conductivity formalism. The dc conductivity and hopping frequency are thermally activated and their activation energies found to be in the range of 0.79–0.85 eV. The variation of dielectric permittivity with frequency is attributed to ion diffusion and polarization occurring in the NASICONtype vitreous materials. Scaling in conductivity and permittivity shows that the relaxation mechanisms are independent of temperature for the NASICON-type vitreous materials. © 2004 Elsevier B.V. All rights reserved.

C.R. Mariappan

Papers

Ac conductivity, dielectric studies and conductivity scaling of NASICON materials

Lithium and potassium ion conduction in A3TiB′P3O12 (A=Li, K; B′=Zn, Cd) NASICON-type glasses

Vitrification of K3M2P3O12 (M = B, Al, Bi) NASICON-type materials and electrical relaxation studies

Preparation, characterization, ac conductivity and permittivity studies on vitreous M4AlCdP3O12 (M = Li, Na, K) system

Synthesis, characterization and ion dynamic studies of NASICON type glasses