Mechanical activation of the synthesis reaction of BaTiO₃ from a mixture of BaCO₃ and TiO₂ powders

The influence of long term milling in an attritor of a mixture of BaCO₃ and TiO₂ powders on the reaction synthesis of BaTiO₃ was studied. Thermal analysis (TG and DTA) of the unmilled and milled powders and X-ray diffraction of powders calcined at different temperatures were undertaken. Milling does not change the reaction sequence between BaCO₃ and TiO₂. BaTiO₃ and Ba₂TiO₄ are produced in both kinds of powders. However, milling reduces the formation temperature and accelerates the formation rate of these two phases. The production of final BaTiO₃ is incomplete in the milled powder, probably because of the formation of big crystals of Ba₂TiO₄. As a consequence, the milled powder contains large amounts of Ba₂TiO₄ after calcination at 1200 °C. Milling produces allotropic transformations in TiO₂ from anatase phase, to α-PbO₂-like phase and finally to rutile structure.