Bi(Mg_0.5Ti_0.5)O₃-doped NaNbO₃ ferroelectric ceramics: Linear regulation of Curie temperature and ultra-high thermally stable dielectric response

Sodium niobate (NaNbO₃, NN)-based ferroelectric ceramics have been extensively studied owing to their antiferroelectric (AFE) nature. However, the dielectric properties of NN-based ceramics, which would be beneficial to capacitor devices, gain less research interest. In this study, (1−x)NaNbO₃-xBi(Mg_0.5Ti_0.5)O₃ (NN-xBMT, x = 0, 0.01, 0.02, 0.03, 0.04, 0.05) ferroelectric ceramics were manufactured by a traditional solid state method. Structure and dielectric/ferroelectric properties were studied in detail by X-ray diffraction, dielectric spectrum as well as polarization-electric field hysteresis loops. All ceramic samples show an AFE P phase in the doping range. As x increases, the grain size of studied compositions gradually decreases from 5.36 μm in x = 0 to 2.05 μm in x = 0.05. In addition, the incorporation of BMT plays a regulatory role to the Curie temperature T_C of ceramic samples, which decreases almost linearly from 375 °C x = 0 to 216 °C x = 0.05 at a rate of 33 °C/1 at. %. However, the degree of diffusion for each composition does not change significantly. More importantly, ultra-high thermally stable dielectric responses in a wide temperature range are obtained in NN-xBMT. Especially in x = 0.03, its permittivity is around 500 at room temperature and shows a variation less than 4.4% from 30 to 150 °C. Our results may have some guiding significance for the preparation of NN-based ceramics with specific T_C, and are significantly important for capacitor applications requiring a wide temperature range stability.