Study on the dielectric properties of Mg-doped NaBiTi₆O₁₄ ceramics

With the interest in using lead-free materials to replace lead-containing materials increasing, the use of Na_0.5Bi_0.5TiO₃ (NBT) has come into our sight. We studied the composition of NBT and found that NaBiTi₆O₁₄ ceramics can be compositionally tuned by Mg-doping on the Ti-site to optimize the dielectric properties. In this study, Mg-doped NaBiTi₆O₁₄ (NaBi(Ti_0.98Mg_0.02)₆O_14-δ) ceramics were prepared by a conventional mixed oxide route at different sintering temperatures, and their dielectric properties have been studied at a wide temperature range. X-ray diffraction (XRD) patterns of the NBT-based ceramics indicate that all samples have a pure phase without any secondary impurity phase. The experimental data show that after Mg-doping, the relative permittivity and dielectric loss become lower at 1040, 1060, and 1080℃ except 1020℃ and at different frequencies from 10 kHz, 100 kHz to 1 MHz. Take 1060℃ for example, when the sintering temperature is 1060℃ at 1 MHz, the minimum relative permittivity of NaBiTi₆O₁₄ is 32.9 and the minimum dielectric loss is 0.01417, the relative permittivity of NaBi(Ti_0.98Mg_0.02)₆O_14-δ under the same condition is 25.8 and the dielectric loss is 0.000104. We explored the mechanism of Mg-doping and surprisingly found that the dielectric property of NaBi(Ti_0.98Mg_0.02)₆O_14-δ becomes better owing to Mg-doping. Thus, NaBi(Ti_0.98Mg_0.02)₆O_14-δ can be used in microwave ceramics and applied to new energy materials.