The rate-determining mechanism in the sintering of undoped nonstoichiometric barium titanate

High-purity undoped nonstoichiometric BaTiO3 powder of TiO2-excess and BaO- excess has been pressureless-sintered in the range of 1215-1340 degrees C u sing conventional tube furnace. Low temperature sintering of the TiO2-exces s composition results in the characteristic plate-like grains grown along t he {111} plane. Surface energy anisotropy is proposed to account for the an omalous microstructural development and low final sintered density. The act ivation enthalpy values (Delta H) deduced from isothermal sintering are 522 +/- 130 and 396 +/- 16 kJ mol for the TiO2-excess and BaO-excess compositi on, respectively. The rate-determining mechanism for the solid-state sinter ing of the undoped nonstoichiometric BaTiO3 powder is discussed. (C) 2000 E lsevier Science Ltd. All rights reserved.