HARDNESS STUDIES AND FRACTURE-BEHAVIOR ON FLUX-GROWN YFEO3 SINGLE-CRYSTALS

Results of Vickers' microhardness (H-v), fracture toughness (K-c), bri ttleness index (B-i) of (110) and (001) faces of flux-grown yttrium or thoferrite crystals: in the load range of 10-100 g, are given. The cra cks are classified into Palmqvist and median types. The transition fro m Palmqvist to median type of cracks is shown to take place when the a pplied load exceeds 50 g. Application of the formula of NIHARA et al. for only median cracks leads to calculation of more precise values for fracture toughness and brittleness index than what was reported earli er (BAMZAI et al.) as an average value.