Barium titanate (BaTiO3, BT) ceramics with various grain sized are prepared by spark plasma sintering (SPS), and conventional sintering. The starting powder was prepared by a hydrothermal method. The average grain size of the powder is approximately 50 nm. The piezoelectric properties were measured by a resonant-antiresonant frequency method and d33 values were evaluated. The additional annealing in oxygen of the BT ceramics obtained by SPS in effective in raising their piezoelectic d33 coefficients. Piezoelectric d33 coefficients were measured for the d33 meter of the BT ceramics prepared by SPS at 950 degrees C and annealed at 1000 degrees C in air for 12h and the same ceramics with additional annealing at 1000 degrees C in oxygen for 100h are 68 and 93 pC/N, respectively.
