Dependence of the Ratio of Piezoelectric Coefficients on Density and Composition of Barium Titanate Ceramics
The ratio of piezoelectric coefficients -d33d31 was found to decrease from about 2.5 for polarized barium titanate ceramic of high porosity to 2.2 for porosity near zero. The ratio increases up to 2.9 for ceramic with 2% porosity containing 12 weight% calcium titanate. For single crystal barium titanate the ratio -d33d31 is 2.5, which checks well with x-ray data for the ratio of thermal strain in the c and a directions. The value for ceramics of lowest porosity does not, therefore, approach that for the single crystal.