Electrochemical Impedance spectroscopy study of AgI-Ag2O-MoO3 Glasses: Understanding the Diffusion, Relaxation, Fragility and Power Law Behavior

TL;DR

This study uses electrochemical impedance spectroscopy and Raman analysis to explore ion diffusion, relaxation, and structural features in AgI-Ag2O-MoO3 glasses, revealing their complex conduction behavior and phase characteristics.

Contribution

It provides new insights into the correlation between diffusion, relaxation, fragility, and power law behavior in these glasses, including the identification of structural phases and the origin of super-linear power law.

Findings

Determined diffusion coefficients, lengths, and relaxation times using Nguyen-Breitkopf method.

Identified fragility threshold and its relation to polymeric phases.

Observed multiple dispersive regimes in AC conductivity with sub- and super-linear behavior.

Abstract

Electrochemical Impedance Spectroscopy and Raman studies are performed on fast ion conducting, AgI-Ag2O-MoO3 glasses, over a wide range of composition to understand the features of structure, ion migration and their correlation. These features essentially involve diffusion and relaxation. The coefficients associated with diffusion process, especially, the diffusion coefficient, diffusion length and relaxation time has been determined by applying Nguyen-Breitkopf method. Besides, by tuning the concentration of the constituents, it is possible to obtain samples those exhibit two important structural characteristics; Fragility and Polymeric phase formation. The present study essentially addresses these issues and endeavors to figure out the corroboration among them. The relaxation behavior, when scrutinized in the light of Diffusion Controlled Relaxation model, ascertains the fragility threshold which is also identified as the margin between the two types of polymeric phases. Simultaneously, it fathoms into the equivalent circuitry, its elements and their behavioral changes with above mentioned features. The power law behavior of A.C. conductivity exhibits three different non-Jonscher type dispersive regimes along with a high frequency plateau. The sub-linearity and super-linearity remain significantly below and above the Jonscher's carrier transport limit, 0.5 < n < 0.9. Finally, by observing the behavior of the crossover between these sub-linear and super-linear (SLPL) regime, an intuitive suggestion has been proposed for the appearance of SLPL; oxygen vacancy formation at higher frequency.