Ceramics-Silikáty 52 (1) 45-48 (2008)

Microstructure and dielectric properties of BaTiO₃–Nb₂O₅–Zn_0.8Mg_0.2TiO₃ ternary system

B. Tang, S. Zhang, X. Zhou, L. Xiang

Ceramics of BaTiO₃–Nb₂O₅–Zn_0.8Mg_0.2TiO₃(ZMT) composition were prepared by solid state reaction. The influence of Nb₂O₅ and ZMT addition on phase transition, microstructure, temperature-capacitance change (TCC), temperature dependence of permittivity and Curie temperature (Tc) have been studied profoundly. With only 1 mol% Nb doping, a single perovskite phase has been observed. Nevertheless, when Nb amount exceeded 2 mol%, a secondary phase of BaTiNb₄O₁₃ was observed. The SEM and XRD analysis showed that the solubility of ZMT in BaTiO₃ with 1 mol% Nb is < 4 mol%. It was observed that for a fixed amount of ZMT dopant increasing the amount of Nb content decreased the room temperature dielectric constant and shifted the Tc to higher temperatures. Finally, a new dielectric sintered in air atmosphere at intermediate temperature (1180°C) was obtained with large permittivity, low dissipation factor and high resistivity, meeting EIA X8R specification.

Keywords: Barium titanate; Dielectric properties; X8R; Curie temperature; ZMT; Niobium