Influence of Nano Barium - Titanate Glass Coating Layer on the Dielectric Properties of Zirconia

Abstract

Dielectric materials used in electrical energy storage devices, must have a high dielectric constant with low dielectric losses. In this work, new method was used to improve the dielectric properties of 3Y-TZP (3% mol yttria tetragonal zirconia polycrystalline) ceramics, by adding different percentages of nano barium titanate (BaTiO3) to glaze mixture. 3Y-TZP specimens were sintered at a 1450 oC, and the glaze layer was fired at 800 °C. BaTiO3 increased from 40 wt% to 60% resulting an increase in the crystalline size. As well, both dislocation density and lattice strain were decreased down to 175×108 lines / mm2 and 12×10-3, respectively. The dielectric constant values were doubled up to 75.6 for glass-coated specimens when adding 60 wt% BaTiO3. This increase was accompanied by an increase in tangent losses value up to 0.026. Electrical breakdown Ebr of specimens was measured with the number of repeat breakdown and at different ramp rate of the voltage RRV. The Ebrmax is 55.7 kV / mm at RRV 5 kV / s for coated specimens without BaTiO3. A drop in Ebr has reached a minimum value of 41.7 kV/s at the same RRV. Various phenomena accompanied the Ebr, including electromechanical, electrothermal and electrical treeing.