Ionic Conductivity Of Solid Oxides Hxag1-xtawo6.NH2O: Microstructural Aspects

TL;DR

This study investigates the microstructural factors affecting ionic conductivity in solid oxides, revealing how porosity and phase structure influence impedance behavior and activation energies during temperature cycling.

Contribution

It provides a microstructural explanation for anomalous impedance responses in doped pyrochlore materials, linking porosity and phase structure to conductivity behavior.

Findings

Sample with x=0.20 shows anomalous conductivity during cooling.

High porosity sample fits the 'easy-path' model.

Activation energies vary with concentration and temperature cycle.

Abstract

A study of impedance spectroscopy was done for the electrical characterization of pyrochlore materials. The experiment consisted of measurements of the dependence of the impedance of such systems with the temperature during heating (25 to 110 {\deg}C) and cooling (110 to 25 {\deg}C). The goal was to try to avoid the effect of humidity in the impedance spectrum. However, for the sample with x = 0.20, we get an anomalous response of the conductivity during the cooling process. To explain this result, we performed micro-structure characterization in this sample and in the samples with x = 0.80 and 0.67. The result is that the sample with x = 0.20 is well characterized by the model "easy-path" because it has high porosity while the other two must have phase precipitate structure type Suzuki. These results served to explain why the anomaly on the Arrhenius plot occurred only in the 0.20 concentration sample: microstructure difference. In this study we can also note that the doped samples had a dependence of activation energies related to the rates of concentration. Except for the sample with concentration rate of 0.20, the activation energies during cooling are among the values of 0.60 and 0.23 eV of their pure counterparts which are registered in the literature.