Ion dynamics in mechanochemically synthesized amorphous fast ionic conductor Ag 2S–Sb 2S 3

Abstract

Frequency dependent electrical conductivity ( σ′) of mechanochemically synthesized amorphous fast ion conductors (FICs) xAg 2S–Sb 2S 3 ( 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, σ′ ( ω)= σ dc( T)+ A( T) ω n , does reproduce the shape of σ′ ( ω) spectra, the σ dc( T) 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, σ′ 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).