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 anal ysis (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 Ba2TiO 3 are produced in both kinds of powders. However, milling reduces the forma tion temperature and accelerates the formation rate of these two phases. Th e production of final BaTiO3 is incomplete in the milled powder, probably b ecause of the formation of big crystals of Ba2TiO4. As a consequence, the m illed powder contains large amounts of Ba2TiO4 after calcination at 1200 de grees C. Milling produces allotropic transformations in TiO2 from anatase p hase, to alpha-PbO2-like phase and finally to rutile structure. (C) 2000 El sevier Science Ltd and Techna S.r.l. All rights reserved.