Influence of sintering and annealing temperature on grain boundary barrier layer capacitors in a modified reduction-reoxidation method

Abstract

To produce grain boundary barrier layer capacitors with a simpler fabrication process and more-stable dielectric characteristics, a modified reduction-reoxidation method was developed. Nb2O5-doped (Ba0.8 Sr0.2)(Ti0.9 Zr0.1)O3 (BSTZ) was calcined at 1170 °C for complete formation of ABO3 phases. After calcination CuO was added to BSTZ as a liquid-phase promoter and insulating boundary layer material. The ceramics were sintered in a reducing atmosphere, and then the fired samples were annealed in air to reoxidize the reduced CuO to form insulating layers. The dielectric constant of the fabricated capacitors was decreased for higher annealing temperature, longer annealing time and smaller grain size. The loss tangent of the fabricated capacitors was increased for BSTZ with more CuO added, and was almost unchanged with annealing temperature, annealing time and grain size because of the existence of an insulating boundary layer material (CuO).