Grain‐Boundary Diffusion of Strontium in (La,Ca)CrO ₃ Perovskite‐Type Oxide by SIMS

The grain‐boundary‐diffusion coefficient ( D gb ) of strontium in La 0.9 Ca 0.13 CrO 3‐δ was determined by secondary‐ion mass spectrometry (SIMS), using two different measurement modes: depth profiling from the surface and line scanning on the fracture surface. The depth profiles that were sputtered by an O 2 + ‐primary‐ion beam gave two slopes of strontium concentration profiles, which corresponded to grain (bulk) and grain‐boundary diffusion. The depth profiles were fitted to an appropriate equation that gave the grain‐ (bulk‐) and grain‐boundary‐diffusion coefficients ( D bulk = 6.5 × 10 ‐20 m 2 /s and D gb = 1.6 × 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 La 0.9 Ca 0.13 CrO 3‐delta was measured by a low‐energy O 2 + ‐primary‐ion beam. The line‐scanning measurement enabled us to successfully determine the strontium concentration profiles around the grain boundary. However, the D gb value that was obtained via the line‐scanning mode was 6.0 10 −13 m 2 /s, which was a factor of 100 greater than that which was obtained by the depth‐profile mode. Comparison between the depth‐profile and line‐scanning modes will require additional careful examination.