ELECTRONIC TRANSPORT-PROPERTIES OF ZRTIO4 AT HIGH-TEMPERATURE

Electrical conductivities, using the four-probe dc method, have been measured for Zr1.012Ti0.988O4 and Zr-1.009 Ti0.986Y0.005O4 between 1073 and 1523 K from oxygen fugacity (1.013 x 10(5) Pa as a standard state) of 10(-20) to 1. Thermoelectric power has also been measured for Zr1.012Ti0.988O4. Both n- and p-type conductivities are found with the dependence of - 1/4 and 1/4 powers of po(2), respectively, and no indication of an ionic conductivity is observed. A defect model has been proposed wherein an extrinsic oxygen vacancy formation is predominant, in which the concentration of oxygen vacancy is determined by the amount of lower-valent impurities or dopants, and excellent agreement is found between experimental and calculated results. The partial conductivity of electrons showed a strong correlation with the anomalous expansion of the c-axis.