High-temperature creep of polycrystalline BaTiO₃

Compressive creep of dense BaTiO₃ having linear-intercept grain sizes of 19.3–52.4 μm was investigated at 1200–1300 °C by varying the oxygen partial pressure from 10² to 10⁵ Pa in both constant-stress and constant-crosshead-velocity modes. Microstructures of the deformed materials were examined by scanning and transmission electron microscopy. The stress exponent was ≈1, the grain-size dependence was ≈1/d², and the activation energy was ≈720 kJ/mole. These parameters, combined with the microstructural observations (particularly grain displacement 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 pressure dependence, diffusion was probably controlled extrinsically.