ANISOTROPIC MICROHARDNESS IN SINGLE-CRYSTAL AND POLYCRYSTALLINE BATIO3

The room-temperature hardness of single-crystal and dense polycrystall ine BaTiO3 was investigated by microindentation. The longer diagonal o f the Knoop indenter was oriented either parallel or perpendicular to the poled axis of the material. The hardness of the unpoled sample was isotropic. However, hardnesses in the poled samples were anisotropic, with the highest hardnesses resulting when the longer diagonal was pa rallel to the poled axis. The hardness anisotropy may be due primarily to residual stresses caused by the piezoelectric coupling effect. (C) 1998 Chapman & Hall.