GRAIN-SIZE DEPENDENCE OF DIELECTRIC-PROPERTIES OF ULTRAFINE BATIO3 PREPARED BY A SOL-CRYSTAL METHOD

Ultrafine BaTiO3 prepared by a decomposition of an organometallic crys tal with unity of Ba/Ti ratio (sol-crystal method) has been characteri zed. While the as-prepared product resulting from the decomposition of the organometallic crystal at room temperature was BaTiO3 with pseudo -cubic structure, the well-crystallized tetragonal polymorph was obtai ned by firing the as-prepared product above 1000 degrees C. Residual o rganic compounds, CO32- and OH- ions in the samples prevent the grain growth and tetragonal distortion of BaTiO3. We obtained quite higher r oom temperature permittivity (3700) at 1 kHz for the sample fired at 1 200 degrees C than that (630) prepared by conventional solid-state rea ction starting from BaCO3 and TiO2. Such a high value was probably due to the accomplishment of homogeneous cation stoichiometry, which was achieved by this preparation method via the organometallic crystal wit h stoichiometric Ba/Ti ratio.