Tuning of high-temperature dielectric properties in the system (Bi0.5Na0.5)TiO3-BaTiO3-CaZrO3

Solid solutions of the (1-x)(0.94Bi(0.5)Na(0.5)TiO(3)-0.06BaTiO(3))-xCaZrO(3) system are regarded as promising dielectrics for high-temperature capacitors as they exhibit a remarkable flat trend of the permittivity over a large temperature range coupled with comparable low dielectric losses. In this work, the composition 0.8 (0.94Bi(0.5)Na(0.5)TiO(3)-0.06BaTiO(3))-0.2CaZrO(3) was chosen in an attempt to optimize especially the high temperature dielectric properties above 200 degrees C. In particular, the influence of excess bismuth to account for element losses caused by evaporation, and the effect of manganese as acceptor dopant are reported. Conventional solid-state reaction route was used to synthesize selected compositions. X-ray diffraction was used to confirm a pseudo-cubic perovskite main phase in all examined compositions, although small traces of a zirconia secondary phase were also detected. All samples exhibit an expected flat trend of the relative permittivity with a maximum deviation of the permittivity lower than 15% between -80 degrees C and 300 degrees C. The unmodified base composition shows small dielectric loss (<2%) between -55 degrees C and 265 degrees C. By using small quantities of manganese doping, the small-loss temperature range was extended (-70 degrees C and 300 degrees C). Excess bismuth also affects the temperature-dependent dielectric losses, resulting in a narrowed temperature range, eventually limiting the application possibilities.

Automated summary

The study focused on optimizing alloy composition to improve high-temperature dielectric properties, and investigated the effects of excess bismuth and manganese doping on performance. The results showed that the addition of small amounts of manganese extended the low-loss temperature range, while excess bismuth limited the application temperature range.