GRAIN-BOUNDARY DIFFUSION OF STRONTIUM IN (LA,CA)CRO3 PEROVSKITE-TYPE OXIDE BY SIMS

The grain-boundary-diffusion coefficient (D-gb) of strontium in La0.9C a0.13CrO3-delta was determined by secondary-ion mass spectrometry (SIM S), using two different measurement modes: depth profiling from the su rface and line scanning on the fracture surface, The depth profiles th at were sputtered by an O-2(+)-primary-ion beam gave two slopes of str ontium concentration profiles, which corresponded to grain (bulk) and grain-boundary diffusion. The depth profiles were fitted to an appropr iate equation that gave the grain- (bulk-) and grain-boundary-diffusio n coefficients (D-bulk = 6.5 x 10(-20) m(2)/s and D-gb = 1.6 x 10(-15) m(2)/s in air at 1273 K, respectively). Initially, to obtain the D-gb value via the SIMS line-scanning measurement, the fracture surface of La0.9Ca0.13CrO3-delta was measured by a low-energy O-2(+)-primary-ion beam. The line-scanning measurement enabled us to successfully determ ine the strontium concentration profiles around the grain boundary. Ho wever, the D-gb value that was obtained via the line-scanning mode was 6.0 X 10(-13) m(2)/s, which was a factor of 100 greater than that whi ch was obtained by the depth-profile mode. Comparison between the dept h-profile and line-scanning modes will require additional careful exam ination.