Dielectric and piezoelectric properties of Bi12TiO20-xNa0.5Bi0.5TiO3 polar composite ceramics

Bi12TiO20-Na0.5Bi0.5TiO3 (BT-NBT) polar composite ceramics with BT/NBT molar ratios of 1:20, 1:12, 1:5, 1:3 and 1:1 were prepared using a thermal gradient sintering method. The dielectric and piezoelectric properties of samples were investigated as a function of the Bi12TiO20 volume fraction. With increasing the Bi12TiO20 content, the relative dielectric constant (εr) decreased and the piezoelectric coefficient (d33) increased. The variation of the εr values was found to fit closely to theoretical values obtained with the cube model. The strongest piezoelectricity was obtained for the sample with a BT/NBT molar ratio of 1:1, which exhibited a d33 of 21.5 pC/N and a piezoelectric voltage constant (g33) of 40 × 10−3 Vm/N. BT-xNBT polar composite ceramics exhibited high depoling temperatures and near-zero temperature coefficients of resonant frequency; therefore, they are promising candidates for high-temperature piezoelectric applications.