ELECTRICAL-CONDUCTIVITY AND CHEMICAL DIFFUSION-COEFFICIENT OF SR-DOPED LANTHANUM CHROMITES

The electrical conductivity and chemical diffusion coefficient of Sr-doped lanthanum chromites were measured as a function of oxygen partial pressure (P-O2) and temperature, and the results were discussed in light of defect chemistry. The electrical conductivity was independent of P-O2 and in proportion to the Sr-content at high P-O2, while at low P-O2), the conductivity decreased exponentially with decrease of P-O1. The P-O2 dependence was reasonably interpreted by the simple point defect model in which Sr'(La), Cr-Cr(.), and V-0(..) are assumed as predominant defect species. The chemical diffusion coefficient derived from time dependence of electrical conductivity after an abrupt change of P-O2 in the atmosphere increased with decrease of P-O2, which was elucidated by a combination of the ambipolar diffusion theory and defect chemical analysis. The vacancy diffusion coefficient calculated from the measured chemical diffusion coefficient was independent of the vacancy concentration at not too high vacancy concentrations, suggesting that the vacancies are non-interactive and flee.