Grain boundary diffusion and grain boundary chemistry of Cr-doped magnesium oxide

The grain boundary product D' delta (where D' is the grain boundary diffusion coefficient and delta is the grain boundary width) of Cr51 in MgO and Cr-doped MgO was determined at 1200 to 1450 C for Cr(3+) concentrations of 0 to 0.56 atom percent. By assuming a grain boundary width to be between 100 and 1000 A the grain boundary diffusion coefficients are 100,000 to 1,000,000 times larger than the volume diffusion coefficients. D' delta increased with increasing CR(3+) concentration, but the activation energy for diffusion of 180 + or - 8 kJ/mole was the same for all specimens.