Phase evaluation and temperature stability in BaTiO₃-BiScO₃ modified Na_0.5Bi_0.5TiO₃ lead-free ceramics

Structural and dielectric thermal stability in (1− 2x)Na_0.5Bi_0.5TiO₃ (NBT)–xBaTiO₃ (BT)-xBiScO₃ (BS) for x = 0.01, 0.03, 0.05, 0.07, and 0.09 lead-free ceramics were first investigated. X-ray diffraction studies revealed composition-driven phase transitions in NBT–BT–BS ceramics, wherein the crystal structure changed from rhombohedral to a mixed phase of cubic and tetragonal with increasing x. Dielectric measurements showed a low-temperature dielectric dispersion and a high-temperature dielectric maxima for all the ceramic samples. This was attributed to the presence of two types of polar nano region (PNR), such as low-temperature PNRs and high-temperature PNRs. The composition of x = 0.05 exhibited a relatively high permittivity of 3250 at 250 °C (10 kHz) maintaining thermal stability varying no more than ± 15% from temperature range of 168 to 400 °C. These results suggest that the addition of BT–BS to the NBT ceramics can also be suitable candidates for high-temperature capacitor applications.