The effect of Mg2+, Ca2+, Sr2+, Sc3+, Yb3+, Y3+, Gd3+, La3+, Ti4+, Zr4+ and Nb5+ upon grain-boundary mobility was investigated at temperatures ranging from 1270 to 1420C. The results supported the suggestion that cation interstitial transport was the rate-limiting step. A marked solute drag effect was observed in the case of diffusion-enhancing dopants such as Mg2+ and Ca2+ which, at high concentrations, could suppress grain boundary mobility. Very undersized dopants, such as Mg, Sc, Ti and Nb, tended to enhance grain boundary mobility markedly. This was attributed to large distortions, of the surrounding lattice, that appeared to facilitate defect migration.

P.L.Chen, I.W.Chen: Journal of the American Ceramic Society, 1996, 79[7], 1793-800