Research on electrical conductive properties of thulium-doped calcium zirconate solid electrolyte

To further investigate the electrochemical performance of Tm doped CaZrO₃ electrolyte, the CaZr_1−xTm_xO_3−α (x = 0, 0.025, 0.05, 0.075 and 0.1) solid electrolyte specimens were prepared by high temperature solid state method. The phase structure and microstructure of the electrolyte samples were analyzed by Raman spectrum, XRD and SEM. The electrical conductivity of the specimen was measured at the temperature of 673∼1373K in hydrogen-rich and oxygen-rich atmosphere by the two-terminal AC impedance spectroscopy method. The H/D isotope effect of the specimen at different temperature was tested to confirm the dominant conducting carrier in predetermined temperature and atmosphere. It is found that proton is the dominant charge carrier both in oxygen-rich and hydrogen-rich atmosphere at the lower temperature below 1073 K. However, at higher temperature above 1073K, the predominant charge carrier seems to be oxygen ion vacancy in hydrogen-rich, whereas to be electron hole in oxygen-rich atmosphere, based on the analysis of the atmospheric dependence of the electrical conductivity. Moreover, partial conductivities of conducting species, the active doping amount of Tm and the standard Gibbs free energy changes for interstitial proton production by dissolution of water and hydrogen in Tm doped electrolyte were estimated based on crystal defect chemistry theory.