High temperature dielectric stable (1-x)[(Na_0.5Bi_0.5)_0.92Ba_0.08]_0.955La_0.03TiO₃-xNaNbO₃ system with ultra-low dielectric loss range through optimizing the defect chemistry

High permittivity and low dielectric loss are important for the application of high-temperature dielectrics. In present study, high temperature dielectrics based on (1-x) [(Na_0.5Bi_0.5)_0.92Ba_0.08]_0.955La_0.03TiO₃-xNaNbO₃ compositions were synthesized by a conventional solid-state reaction method. The microstructure, dielectric, ferroelectric and electrical properties were systematically investigated. All the samples show relatively high permittivity and excellent low dielectric loss range from ∼90 °C up to 400 °C. Impressively, the composition x = 0.06 shows a high permittivity of 2436 at 150 °C (1 kHz), (ε_r−ε_r150°C)/ε_r150°C varying no more than 15% in the temperature range of 54 °C–344 °C together with a low loss (tanδ≤0.02) range between 92 °C and 400 °C. By developing highly-localized complex defect-dipoles with La and NaNbO₃ dopants to restrain the mobility of oxygen vacancy, as verified by XPS and resistivity-temperature results, the dielectric loss is limited to rather low values. Hence, the current system will be a promising candidate in high temperature ceramic capacitors.