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Abstract: Nanocrystalline Li2Ni1−x Mg x TiO4 powders were synthesized using a sol–gel technique. They were crystallized in cubic rock salt phase with space group Fm-3m. The synthesis was carried out in nitrogen atmosphere using citric acid as fuel. AC electrical properties of the nanocrystalline Li2Ni1−x Mg x TiO4 were investigated by complex conductivity and impedance. The scaling behavior in the electrical conductivity and impedance confirmed the time temperature superposition principle of relaxation mechanism. [Copyright &y& Elsevier]

Abstract: Nano-crystallites of Li1.3Ti1.7Al0.3(PO4)2.9(VO4)0.1 NASICON type material are prepared by means of solid-state reaction of a stoichiometric mixture after milling it for 22 and 55h. The milling reduces the average crystallite size of the ceramic to 80 and 60nm, respectively. Mechanical milling changes structural parameters and the strain induced at the grain-boundaries plays a major role in improving electrical conductivity. An order of magnitude increase in electrical conductivity is observed in the material milled for 55h compared to the unmilled material, which is also reflected in permittivity loss. Modulus and permittivity representations substantiate the constriction effect of grain-boundaries observed in the complex impedance representation. [Copyright &y& Elsevier]

Abstract: A new superionic conducting transparent phosphate glasses with composition Li(4+x)Ti x Nb1−x P3O12 (0 ≤ x ≤ 1.0) were prepared by rapid melt quenching. As quenched samples were characterized by X-ray powder diffraction, differential scanning calorimetric and Fourier transform infrared spectroscopy studies. These glasses were found to have high thermal stability parameter and Li4NbP3O12 has been found to have high glass forming ability. Electrical properties of the present glasses were studied by impedance and dielectric spectroscopy in the frequency range 10 Hz–3 MHz in the temperature range 323–523 K. Arrhenius behavior has been observed for all the glass in conductivity, dielectric loss and conductivity relaxation and their activation energies are explained and reported. [Copyright &y& Elsevier]

Abstract: Niobium based glasses of composition Na2NbMP3O12 (where M=Cd, Zn, Pb and Cu) have been synthesized by melt quenching method and characterized by XRD, FTIR and DSC. The ac conductivity measurements have been carried out over wide range of frequencies at different temperatures on these glassy systems. Ac conductivity data are analyzed using conductivity and electric modulus formalisms. The bulk dc conductivity obtained from complex impedance plots follow the Arrhenius behavior and its activation energy matches well with the activation energy obtained from electric modulus formalism. The ac conductivity plot exhibits universal power law features and the temperature dependence of dc and ac conductivity is discussed. The scaling behavior of the ac conductivity and electric modulus spectra with respect to temperature are discussed and reported for these glassy systems. [Copyright &y& Elsevier]

Abstract: The ac electrical conductivity properties of LiTi2(PO4)3 (LTP) polycrystalline material in two different crystallite sizes are compared. Micrometer sized LTP is prepared by conventional solid-state reaction. LTP crystallites of 71nm size are prepared by solid-state reaction of 40h planetary milled stoichiometric mixture. The XRD and SEM are used as characterization techniques. Electrical properties are studied using impedance spectroscopic technique. Ball-milled LTP shows one order increase in grain-interior conduction compared to microcrystalline LTP at 388K. The increase in conduction results from decreased crystallite size. [Copyright &y& Elsevier]

Abstract: Electrical properties of A2.6+x Ti1.4−x Cd(PO4)3.4−x (A=Li, K; x =0.0–1.0) phosphate glasses are investigated over a frequency range from 42Hz to 1MHz at different temperatures. Impedance spectroscopy is used to separate the bulk conductivity from electrode effect of electrical conductivity data. The bulk dc conductivity is Arrhenius activated, with activation energies and pre-exponential factors following the Meyer–Neldel rule. The real part of ac conductivity shows universal power law feature. The variation of dielectric constant with frequency is attributed to ion diffusion and polarization occurring in the phosphate glasses. The frequency dependent imaginary part of electric modulus M″(ω) plot shows non-Debye feature in conductivity relaxation. The Kohlrausch–Williams–Watts stretched exponential function was used to describe the modulus spectra and the stretching exponent β is found to be temperature independent. Scaling in M″(ω) shows that the electrical relaxation mechanisms are independent of temperature for given composition at different temperatures. [Copyright &y& Elsevier]

Abstract: Vitreous phases of K3M2P3O12 (M=B, Al, Bi) NASICON-type materials are prepared and their electrical properties are investigated over a frequency range from 42Hz to 1MHz 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 0.70–0.82eV. The frequency- and temperature-dependent conductivity spectra of individual glasses can be superimposed by means of the Summerfield scaling. [Copyright &y& Elsevier]

Abstract: 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 42Hz to 1MHz. 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 0.79–0.85eV. The variation of dielectric permittivity with frequency is attributed to ion diffusion and polarization occurring in the NASICON-type vitreous materials. Scaling in conductivity and permittivity shows that the relaxation mechanisms are independent of temperature for the NASICON-type vitreous materials. [Copyright &y& Elsevier]

Abstract: Crystalline Na3Bi2P3O12, K3Bi2P3O12 and glassy K3Bi2P3O12 compounds were prepared by solid-state reaction method. The prepared samples are characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy and differential scanning calorimetry. The crystalline materials are found to be orthorhombic. The electrical conductivity measurements on the crystalline and glassy samples show that at ∼373K, the σ DC for crystalline K3Bi2P3O12 (0.81×10−8 S/cm) is about two orders of magnitude higher than the corresponding glassy phase (1.25×10−10 S/cm). The scaling results show that the conductivity relaxation mechanism is independent of temperature. [Copyright &y& Elsevier]

Abstract: The NASICON system Na4.7+x Ti1.3−x (PO4)3.3−x is synthesized for 0.0≤x≤0.6 and investigated the electrical properties in wide range of frequency and temperature. By means of nonlinear least square fitting of appropriate equivalent circuits, the bulk conductivity is separated from electrode effects. Ac conductivity and permittivity data are analyzed by using conductivity formalism. The dc conductivity and hopping frequency activation energies are found to be in the range of 0.56–0.64 eV. The hopping frequency activation energy is in agreement to the activation energy of dc conductivity. The scaling behavior in ac conductivity is studied and observed that the ion dynamics is independent of temperature and composition. [Copyright &y& Elsevier]

Abstract: Electrical properties of A3TiB′P3O12 (A=Li, K; B′=Zn, Cd) NASICON-type glasses are reported over a frequency range from 42 Hz to 1 MHz and at different temperatures. By means of nonlinear least square fitting of the electrical data to appropriate equivalent circuits, the bulk conductivity is separated from electrode effects. The bulk dc conductivity is Arrhenius activated, with activation energies and pre-exponential factors following the Meyer–Neldel rule. The frequency- and temperature-dependent conductivity spectra of individual glasses can be superimposed by means of the Summerfield scaling. However, the master curves of different glasses do not superimpose. We show that this effect is related to the composition dependence of the many-particle displacement function 〈R2(t)〉. [Copyright &y& Elsevier]

Abstract: The non-Debye relaxation (NDR) behavior in disordered solids is characterized either by the empirical form of stretched exponential ϕ(t)=exp[−(t/τ)β] or by the Curie–von Schweidler law j(t)∝t−n. The physical meaning for the exponents β and n is described in terms of energy processes, where the smallness of the exponent β or n characterizes the degree of non-Debye behavior. In the frequency domain, the non-Debye behavior shows dispersion in conductivity σ′(ω)∝ωn and permittivity loss ɛ″(ω)∝ωn−1 above loss peak frequency ωp and are termed as Jonscher universal power law or Jonscher universal dynamic response. In the present article, the universal dynamic response is described using a non-Debye relaxation function ϕ(t)=exp[−t/τ*], where τ*=τg/i(1−g) and τ* is defined as non-Debye relaxation time. Correspondingly, in the frequency domain, the dielectric response function ɛ*(ω)=ɛ∞+[(ɛS−ɛ∞)/(1+igωτg)] has a phase factor ig. The physical meaning for the exponent g is described in terms of energy processes. At the dielectric loss peak frequency, the dielectric loss tan[δp] which signifies the energy dissipation, attains a minimum and it is related to the exponent g. Expressions for real part of the ac conductivity σ′(ω) is derived from the permittivity loss, ɛ″(ω). All experimentally known features of the σ′(ω) and ɛ″(ω) are explained satisfactorily. The present model is used to analyze the experimental data of lithium phosphate glassy system. The results show an excellent agreement both in the conductivity and impedance representation. [Copyright &y& Elsevier]

Abstract: Conductivity dispersion, electric modulus and their scaling are studied for Na3M2P3O12 orthophosphate (M2=Fe2, TiCd, TiZn) glassy and crystallized glassy materials in the frequency range 20Hz to 1MHz at different temperatures (T). The power law and the stretched exponential approaches are used to analyze dispersion data. The DC conductivity σDC of crystallized glass is found to be greater than that of the parent glass. The conductivity scaling is studied with different scaling parameters like hopping frequency , the Summerfield scaling parameter σDCT and modified the Summerfield scaling parameter , where shows the temperature dependence. Ngai''s correlation is also observed between power-law exponent n and stretched exponent . [Copyright &y& Elsevier]