Temperature invariant high dielectric properties over the range 200 °C–500 °C in BiFeO₃ based ceramics

Lead free piezoelectric ceramics (1–x) (0.67Bi_1.05FeO₃–0.33BaTiO₃)–xLiNbO₃ with x = 0.00, 0.015 and 0.030 were prepared by using conventional mixed oxide route. The incorporation of LiNbO₃ into BF–BT system caused no significant change in crystal structure. However, an obvious variation in electrical properties was observed. The x = 0.015 composition showed enhanced ferroelectric and electric field-induced strain properties with dynamic piezoelectric constant S_max/E_max = 440 pm/V at a relatively low field of 40 kV/cm, along with a high working temperature upto T_m = 392 °C. LiNbO₃ addition improved the temperature insensitivity of relative permittivity (ε_r) at high temperatures. At x = 0.030, a near-plateau ε_r ∼5000, extended across the temperature range, 200 °C–500 °C was observed which is advantageous for temperature insensitive dielectric ceramics for high temperature capacitor applications. Large strain and almost temperature invariant ε_r with high working temperature range makes this system suitable for high temperature electronic devices.