CATION DIFFUSION IN (LA,CA)CRO3 PEROVSKITE BY SIMS

Cation diffusion in (La,Ca)CrO3 was examined by two kinds of diffusion experiments: Sr(NO3)(2) solution applied experiment on the La0.75Ca0. 25CrO3 surface and a diffusion couple experiment of La0.95Sr0.05CrO3 / La0.75Ca0.25CrO3, with secondary ion mass spectrometry (SIMS) analysis . The obtained bulk chemical interdiffusion coefficients for Ca-Sr fro m the two different experiments were almost on the same line in the te mperature dependence plots, as follows: D-bulk (cm(2)s(-1)) = 2.66 x 1 0(-2).exp(- 318(kJ mol(-1))/RT) (1173-1673 K). The grain boundary chem ical interdiffusion coefficients for Ca-Sr were obtained by the SIMS d epth profiles with a new fitting equation, as follows: D-gb (sm(2)s(-1 )) = 10.1.exp (- 261 (kJ mol(-1))/RT) (1173-1373 K). For the calculati on of the grain boundary diffusion coefficient, the width of the grain boundary is assumed to be 1 nm. The diffusion coefficient for grain b oundary interdiffusion of Ca-Sr is calculated to be five times higher than that for bulk diffusion at the same temperature. The grain bounda ry diffusion coefficient increased with the 0.66 power of p(O-2), whic h has a relationship with the valence change of Cr at the grain bounda ry. (C) 1998 Elsevier Science B.V. All rights reserved.