Mechanochemical Effect on the Solid State Reaction between Barium Carbonate and Titanium Dioxide

Abstract

The influence of structural distortion and microscopically homogeneous mixing etc., given to powder material as mechanochemical effect by mechanical grinding, on velocity of solid state reaction have been studied in the system of BaCO3-TiO2-. When BaCO$ and TiO2 (anatase) were ground independently in air or in vacuum and together in air, remarkable structural changes were not seen on X-ray diffraction patterns. Whereas, when both compounds were mixed and ground for 48 hours in vacuum (10-2 mmHg), the clear change into amorphous phase by distruction and the rapid growth of secondary particles by strong aggregation occurred between both distorted surfaces were shown. However, the formation of BaTiO, was not confirmed. The formation velocities of 13aTiO0 by heating the ground mixture of J3aCO3 and TiO2 were studied through the X-ray diffraction patterns at high temperature '(10°C/min) and it was found that the formation of BaTiOs were much accelerated by mechanochemical effect. The formation of BaTiO3 started at 500°C and ended at 800°C in the case of the mixture ground for 48 hours in vacuum, while it began at 750°C and terminated at 1100°C in the case of the simple mixture without grinding. Arrhenius plots of some ground mixtures were expressed as a bended line, caused on the difference between reactivity of distorted BaCO3 on the surface and that of undistorted BaCO3 in the center of a particle.