Surface modification of barium titanate powder particles

The surfaces of n-doped barium titanate (BaTiO3) powder particles were modi fied by milling in a Ca(NO3)(2) solution both at room temperature and under hydrothermal conditions before they were analyzed by electron energy loss spectroscopy and transmission electron microscopy down to the nanometer ran ge. The room temperature treated powders showed BaTiO3 particles covered with a CaO/BaO layer. Heating these particles caused a shell of (Ca,Ba)TiO3 solid solution. Under hydrothermal conditions rectangular CaTiO3 crystallites pr ecipitated on the surface of the BaTiO3 grains, which during heating transf ormed into a series of (Ba1-xCax)TiO3 particles. These modifications of the shell structure change the sintering behavior and thus the microstructure as well as the electrical properties of the final ceramics. Especially the room temperature resistance and the voltage withstanding of the ceramic inc reased compared to that of conventionally prepared materials of identical c omposition. (C) 1999 Elsevier Science S.A. All rights reserved.