Ion dynamics in mechano chemically synthesized amorphous fast ionic conductor Ag2S-Sb2S3

Frequency dependent electrical conductivity (a) of mechanochemically synthesized amorphous fast ion conductors (FICs) xAg(2)S-Sb2S3 (x=70, 80, 85) is investigated in the frequency range 5 Hz-13 MHz and temperature range 95-385 K. While the universal dynamic response (UDR) model, sigma(w)=sigma(dc)(T)+A(T)w, does reproduce the shape of sigma(w) spectra, the sigma(dc)(7) and A(T) show anomalous characteristics. Both exhibit two distinct Arrhenius regions, a low temperature region with a lower value of activation energy (E) and a high temperature region with higher value of activation energy. Further the frequency exponent n is a (decreasing) function of temperature, decreasing slowly at lower temperatures but more rapidly at higher temperatures. The correlation E-ac=(1-n)E-dc appears satisfactory in the low temperature region but unsatisfactory at higher temperatures. The isochronal representation of ac conductivity, sigma' vs. 1000/T at different frequencies, reveals the existence of a third regime, which is currently under active discussion and is known as superlinear power law (SLPL). (c) 2005 Elsevier B.V. All rights reserved.