Dielectric Constant of Barium Titanate Powders Near Curie Temperature

Impedance spectroscopy is an effective method to investigate the dielectric properties of powders by dispersing particles in proper liquids. It allows reliable calculation of the dielectric constant by analysis of impedance spectra for a variety of particulate materials. The temperature dependence of the dielectric constant near the Curie temperature was investigated for hydrothermal barium titanate powders suspended in ethylene glycol or butoxyethanol. Room‐temperature measurements revealed that the dielectric constant of hydrothermal BaTiO3 powders was ɛ∼500. After annealing of powders at 1250°C for 1 h, the dielectric constant increased to ɛ∼3000. The temperature dependence of the impedance spectra was determined by conducting measurements within the temperature range from 20° to 150°C. It was shown that hydrothermal BaTiO3 powders with a primarily cubic crystal structure had a suppressed temperature dependence of the dielectric constant near the Curie temperature. The dielectric constant of annealed powders with a tetragonal crystal structure was significantly higher at the Curie temperature similar to the values obtained for sintered bulk barium titanate.