THE INFLUENCE OF THE MILLING LIQUID ON THE PROPERTIES OF BARIUM-TITANATE POWDERS AND CERAMICS

The influence of the milling liquid on the properties of donor-doped ( La3+) semiconducting barium titanate (BaTiO3) ceramics, generated by t he mixed oxide technique, was investigated. Distilled water and propan -2-ol were used as milling liquids. Water was found to have two essent ial effects. First, it dissolves Ba2+ ions out of BaTiO3 grains, thus creating core-shell structures which were confirmed by high-resolution electron microscopy (HREM) and electron energy loss spectroscopy (EEL S). They consist of a 3-5 nm thick TiOx-rich layer followed by a layer (ca. 10 nm thick) with a molar Ba/Ti ratio increasing from 0 to 1. Th ese core-shell structures of the BaTiO3 powder positively affect the s intering behaviour of the greens by the high reactivity of the Ti-rich interlayer. Secondly, water cleans the BaTiO3 powder of acceptor cont aminants, producing ceramics with a low electrical resistivity at room temperature. Propan-2-ol-milled ceramics of a comparable composition show an electrical resistivity up to six orders of magnitude higher, o wing to the compensation of La3+-doping by acceptor contaminants.