Mechanical characteristics of flux-grown calcium titanate and nickel titanate crystals

Results of hardness and fracture studies conducted on different planes of flux-grown CaTiO3 and NiTiO3 single crystals in the applied load range of 0.098-0.98 N, using a Vickers hardness tester, are reported. Microhardness varies non-linearly with load and is best explained by the concept of Newtonian resistance pressure as proposed by Hays and Kendall's law. Different hardness values for different planes suggest an anisotropic character of the hardness in CaTiO3 crystals. The hardness results and the indentation-induced cracking yield the values of the yield strength, fracture toughness and brittleness index for CaTiO3 and NiTiO3 crystals. The classification of cracks and their transition from Palmqvist to Median types is explained.