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 BaTiO 3 phase identified. The Ba 1-x Y x TiO 3 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 BaTiO 3 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 Ba 1-x Y x TiO 3 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.