Authors : Prashant Ambekar
Page Nos : 51-57
Description :
In this paper we report a study of SrCO3: Li2CO3 binary solid electrolyte system, wherein, a Complex Impedance Spectroscopy, Wagner's DC polarization Technique, and the DC Four-Probe methods were used to explore the in-situ AC, DC, bulk, and Surface Electronic Conductivities of the SrCO3: Li2CO3 binary solid electrolyte at various temperatures and under calibrated CO2 gas pressures. A specialized and indigenous sample container with four equidistant, spring-loaded noble metal electrodes and a localized heating system (473-583 K) were used for the four-probe conductivity/resistivity measurements, which has a critical need of equilibrated temperatures under test gas concentrations. During the impedance study at temperatures from 473K to 593 K, it was discovered that the AC bulk conductivity decreased with increasing CO2 gas concentration (from 0.1 to 100%) by about two orders and one order of magnitude, respectively. For both the CO2 concentrations, 0.04 and 10%, surface conductivity changes with temperature similarly exhibited Arrhenius behaviour, with a lower activation enthalpy for lower CO2 concentration. By comparing surface conductivity data with AC bulk conductivity measurements at various CO2 partial pressures and DC conductivity together with sensor response, the change in surface conductivity in the presence of various concentrations of CO2 gas is justified and understood. Utilizing data from active charge transfer, the mechanism, the electronic excitation window was discovered to contain the range of Ea values on CO2 gas adsorption, suggesting the involvement of a novel parameter that must be researched for non-Nernstian response of EC sensors.
