High-temperature creep of polycrystalline BaTiO3

Compressive creep of dense BaTiO3 having linear-intercept grain sizes of 19 .3-52.4 mu m was investigated at 1200-1300 degrees C by varying the oxygen partial pressure from 10(2) to 10(5) Pa in both constant-stress and constan t-crosshead-velocity modes. Microstructures of the deformed materials were examined by scanning and transmission electron microscopy. The stress expon ent was approximate to 1, the grain-size dependence was approximate to 1/d( 2), and the activation energy was approximate to 720 kJ/mole. These paramet ers, combined with the microstructural observations (particularly grain dis placement and absence of deformation-induced dislocations), indicated that the dominant deformation mechanism was grain-boundary sliding accommodated by lattice cation diffusion. Because of the absence of an oxygen partial pr essure dependence, diffusion was probably controlled extrinsically.