The temperature dependence, at 400 to 580C, of <111> grain boundaries with misorientation angles of 38.2 or 40.5 was investigated in bicrystals of 5N-purity, and in the same material after doping it with 10ppm of Ga. It was found that the grain boundary mobility over the above temperature range was increased by minor Ga additions. Both the activation enthalpy and the pre-exponential factor were affected by Ga doping. The orientation dependence of the grain-boundary mobility was strongly reduced, but not entirely removed. The sharp increase in grain-boundary mobility which occurred upon adding Ga to the pure material was explained as being the result of a change in the boundary structure and in the mechanism of boundary migration, due to a pre-wetting phase transition and to the formation of a liquid (or quasi-liquid) Ga-rich layer upon the grain boundary.

D.A.Molodov, U.Czubayko, G.Gottstein, L.S.Shvindlerman, B.Straumal, W.Gust: Philosophical Magazine Letters, 1995, 72[6], 361-8