Transmission electron microscopic investigations were carried out on crystals which had been grown in quartz ampoules, at temperatures of 1020 to 1091C (melting point = 1092C), by using a travelling-heater method (quasi-closed or sealed volumes) or using the Bridgman method (almost stoichiometric melts). A new method was used to prepare thin foils. Two types of grain boundary were observed. These were high-angle misoriented grain boundaries (more than 10º misorientation between adjacent grains) and low-angle misoriented grain boundaries (less than 1º misorientation between adjacent sub-grains). Dislocations with Burgers vectors of (a/6)[112]-type and (a/2)[110]-type were present.

I.V.Sabinina, A.K.Gutakovski, T.I.Milenov, N.N.Lyakh, Y.G.Sidorov, M.M.Gospodinov: Crystal Research and Technology, 1991, 26[8], 967-72