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

Dense BaTiO3 ceramics consisting of submicrometer grains were prepared usin g the spark plasma sintering (SPS) method. Hydrothermally prepared BaTiO3 ( 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 p rocess. 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 BaTiO3 coexisted with tetragonal BaTi O3 at room temperature in the SPS pellets, even when well-defined tetragona l-phase BaTiO3 powder was sintered at 1100 degrees and 1200 degrees C and a nnealed at 1000 degrees C, signifying that the SPS process is effective for stabilizing metastable cubic phase. The measured permittivity was approxim ate to 7000 at 1 kHz at room temperature for samples sintered at 1100 degre es 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.