Rates of change in high temperature electrical resistivity and oxygen diffusion coefficient in Ba sub 2 YCu sub 3 0 sub x.

The change in electrical resistance with time for bulk, thick film, and thin film Ba sub 2 YCu sub 3 0 sub x at atmospheric pressure is described as a function of the oxygen partial pressure (100 to 0.001%) and temperature (320degrees-750C). The potential usefulness of these materials as oxygen sensors is demonstrated. The rate of equilibration is faster during oxygen uptake than during its loss. Time constants, tau, to reach equilibrium (1/e remaining), qualitatively scale with sample dimensions. For a 1micron film at 600C, tau=1 sec for the range of P sub (02) from 100% to 0.01%. The rate increases markedly with increasing P sub (02). The actual resistance decreases with P sub (02) at a rate of log p/log P sub (02) = 0.4 at 700C showing adequate sensitivity for sensor purposes. Times for the transient resistance change in the sample were used to estimate the oxygen diffusion coefficient in the ceramic. The diffusivities obtained are 4x10 sup (-11 - 1x10 sup (-12) cm sup 2 /sec in the 435degree-320C range, with an activation energy of ~27 kcal/mole.