The Ca tracer diffusion coefficient was determined by using an HNO3 acid solution application method which involved 44Ca(NO3)2. The diffusion profiles of 44Ca in the air-sintered material were measured by means of secondary ion mass spectrometry, using bombardment with primary O2+ ions. The diffusion coefficients were determined, for both the bulk and the grain boundaries (using various annealing conditions), from the secondary ion mass spectrometric depth concentration profiles of 44Ca. The 44Ca diffusion coefficients for the bulk ranged from 10-16 to 10-14cm2/s, at temperatures ranging from 1173 to 1373K. The 44Ca diffusion coefficients for grain boundaries were 5 to 6 orders of magnitude higher than those for the bulk. The order of magnitude, and activation energy, for 44Ca bulk diffusion were similar to those for bulk Ca-Sr interdiffusion. A similar diffusion mechanism for the bulk was therefore assumed to apply to tracer diffusion and chemical interdiffusion in the present material. The grain boundary diffusion coefficient for 44Ca had a higher value than that for Ca-Sr interdiffusion.

Calcium Tracer Diffusion in (La,Ca)CrO3 by SIMS. T.Horita, M.Ishikawa, K.Yamaji, N.Sakai, H.Yokokawa, M.Dokiya: Solid State Ionics, 1999, 124[3-4], 301-7