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

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. (c) 2005 Elsevier B.V. All rights reserved.