EXPERIMENTAL-DETERMINATION OF OXYGEN PERMEATION FLUX THROUGH BULK ANDGRAIN-BOUNDARY OF LA0.7CA0.3CRO3

Oxygen permeation flux through La0.7Ca0.3CrO3 was determined by an ele ctrochemical method. Yttria-stabilized zirconia (YSZ) was used as an o xygen pump/sensor to apply an oxygen potential gradient over the sampl e, and the steady state current was recorded. The oxygen vacancy diffu sion coefficient, D-V, was determined to be 1 x 10(-5) cm(2) s(-1) ass uming a random defect model. The tracer exchange experiment was perfor med at 1273 K in O-18 enriched O-2 (0.2 bar), and the sample was analy zed by a depth profiling and imaging technique using a secondary ion m ass spectrometer (SIMS). The existence of fast diffusion paths along g rain boundaries was confirmed. The bulk tracer diffusion coefficient, D-, was calculated to be 2 X 10(-12) cm(2) s(-1) in air, which was ab out 6 times higher than that expected from the electrochemical measure ment.