IMPEDANCE SPECTROSCOPIC STUDY OF THERMODYNAMICS AND KINETICS OF A GD-DOPED BACEO3 SINGLE-CRYSTAL

An impedance spectroscopic investigation on a Gd-doped BaCeO3 single c rystal is reported in which the electronic and ionic properties of the material have been studied systematically between 800 degrees C and 1 200 degrees C under well defined oxygen partial pressures. For the fir st time, the conductance, the diffusion coefficients and the concentra tions of the individual defects in a single crystal have been determin ed as a function of temperature and oxygen partial pressure. The ionic transport numbers are calculated in the light of the conductivity dat a. The defect structure of the material is discussed in the framework of point defect chemistry and the quasi-chemical reaction constants ar e determined. Based on the data acquired, the electron holes are sugge sted to be large polarons, whereas the electrons are small polarons.