Microhardness of Bi12SiO20, Bi12TiO20, and Bi12GeO20 Monocrystals

The microhardness, H, of sillenite-type monocrystals of undoped Bi₁₂SiO₂₀, Bi₁₂TiO₂₀, Bi₁₂GeO₂₀ and Cr-, Fe-, Mn- doped Bi₁₂SiO₂₀ has been investigated. The dependences of H on the surface treatment, dopants and orientation of the materials have been established. It was found that the H and dislocation density, N_d, distribution along the diameter of the sample for undoped (100)-Bi₁₂SiO₂₀ are of M- and W-shape, respectively.