The surfaces of n-doped barium titanate (BaTiO3) powder particles were modified 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 range. 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 precipitated on the surface of the BaTiO3 grains, which during heating transformed 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 increased compared to that of conventionally prepared materials of identical composition. (C) 1999 Elsevier Science S.A. All rights reserved. [References: 15]

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