Properties of yttrium-doped barium titanate ceramics with positive temperature coefficient of resistivity and a novel method to evaluate the depletion layer width

Abstract Yttrium-doped barium titanate ceramics with positive temperature coefficient of resistivity (PTCR) are prepared by the sol-gel technique. The gel powder shows a size distribution around 0.18 µm with a tetragonal BaTiO3 phase identified. The Ba1-xYxTiO3 ceramics are sintered in a reducing atmosphere and oxidized in air. The grain size of the ceramics grows from 1.3 to 1.6 µm when Y-doping amount increases from 1.0% to 2.8%. The electrical properties of room temperature resistivity, PTCR jump and impedance spectroscopy are studied. A novel mathematical method is proposed to evaluate the depletion layer width of the BaTiO3 ceramics based on the dependence of room temperature resistivity on the donor density. The widths of depletion layer of 185 nm are evaluated for the Ba1-xYxTiO3 ceramics sintered at 1150 °C. The donor energy level and Fermi level are found to be essential factors that determine the width of depletion layer.