Dielectric, piezoelectric and conduction properties of yttrium acceptor-doped BaTiO₃ ceramics

BaTi_1−xY_xO_3−x/2 ceramics were prepared by using a solid state reaction process. All the samples have a tetragonal structure below the solution limit of 3 at.%. And the doping of Y³⁺ inhibits the grain growth of BaTiO₃ ceramics. In addition, substitution of Y³⁺ at B-site in BaTiO₃ leads to an increase of Curie temperature (Tc). Specifically, the sample with x = 0.015 has the raised Tc temperature (136 °C) and exhibits a larger electric field induced strain (0.27 %) at the electric field of 65 kV/cm and room temperature. Besides, oxygen loss is restrained due to the incorporation of Y³⁺ in BaTiO₃. Conductivity of the sample with x = 0.005 is dominated by a p-type conduction in air and oxygen, while in nitrogen, oxygen loss leads to it changes to an n-type conduction. However, the sample with x = 0.02 behaves a mixed conduction in oxygen, air and nitrogen, in which the species responsible are primarily O²⁻ ions and holes.