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.