DEFECT STRUCTURE AND N-TYPE ELECTRICAL PROPERTIES OF SrCe_(0.95)Eu_(0.05)O_(3-δ)

摘要

The effect of defect structure on the electrical conductivity for Eu-doped SrCeO_3 was studied in a reducing range of P_(H_2), P_(H_2O), P_(O_2). A defect model was derived and verified by computational simulation against both electrical conductivity data and Brouwer-type defect equilibria. At higher temperatures, part of the conductivity is due to oxygen vacancies and electrons. At low temperature, protonic conduction tends to dominate. The measured total conductivity is proportional to P_(O_2)~(-1/8) in the temperature range of 650 -750°C, and to P_(O_2)~(-1/6) at 800°C in wet atmospheres, because of a transition from ionic- to electronic-dominant conduction. The results agree with a derived defect model based on the equilibrium equation for the valence change of Eu ions between trivalent and divalent.