Effects of BiNbO4 on the microstructure and dielectric properties of BaTiO3-based ceramics

The microstructure and dielectric properties of ternary system BaTiO3 (BT)–Bi0.5Na0.5TiO3 (BNT)–BiNbO4 were investigated. In the case of 1 mol% BNT addition, the Curie point (Tc) of BaTiO3 was increased from 130 to 140 °C. The dielectric constant peak at Tc was markedly depressed with the addition of BiNbO4, whereas an enhancement in the dielectric constant at lower temperature was observed. The addition of BiNbO4 improved the temperature dependence of the dielectric constants of BaTiO3-BNT system ceramics and the temperature coefficient of capacitance curves satisfied the EIA X8R specification with 3–4 mol% BiNbO4. The dielectric constant peak at Tc was suppressed evidently due to over high-sintering temperature. As the BiNbO4 content was increased, the Curie point progressively moved to lower temperatures. SEM indicated that fine and homogeneous grains were observed with 1 mol% BiNbO4 addition. However, secondary phase grains appeared with increasing the BiNbO4 content, which were identified as Ba2TiO4, NaBiTi2O6, and BaTiNb4O13 by XRD. Moreover, the proportion of the secondary phase grains increased as the BiNbO4 content increased.