Preparation of dense BaTiO3 ceramics with submicrometer grains by spark plasma sintering

Dense BaTiO(3) ceramics consisting of submicrometer grains were prepared using the spark plasma sintering (SPS) method. Hydrothermally prepared BaTiO(3) (0.1 and 0.5 pm) was used as starting powders. The powders were densified to more than approximate to 95% of the theoretical X-ray density by the SPS process. The average grain size of the SPS pellets was less than approximate to 1 mu m, even by sintering at 1000-1200 degrees C, because of the short sintering period (5 min). Cubic-phase BaTiO(3) coexisted with tetragonal BaTiO(3) at room temperature in the SPS pellets, even when well-defined tetragonal-phase BaTiO(3) powder was sintered at 1100 degrees and 1200 degrees C and annealed at 1000 degrees C, signifying that the SPS process is effective for stabilizing metastable cubic phase. The measured permittivity was approximate to 7000 at 1 kHz at room temperature for samples sintered at 1100 degrees C and showed almost no dependence on frequency within approximate to 10(0)-10(6) Hz; the permittivity at 1 MHz was 95% of that at 1 kHz.