LAUSR

Abstract This work focuses on the synthesis and characterization of a Pb-free (0.8-x)Na0.5Bi0.5TiO3-0.2SrTiO3-xBiFeO3, 0.00 ≤ x ≤ 0.10 perovskite. The ceramics exhibit significant improvement in some of the key parameters like Tc, dielectric constant, temperature stability, TCe values, etc. XRD patterns suggest 100% perovskite structure (Pseudocubic phase) without any trace of secondary phases. The temperature-dependent dielectric constant of doped ceramics exhibits peculiar response particularly at lower frequencies with er increasing drastically to extraordinarily large values (˃ 50,000 at 1 kHz, and ˃ 12,000 at 10 kHz). Such an abnormal behavior probably arises due to the interfacial polarization caused by the formation of defect dipoles. Further, successive dielectric anomalies appeared around 200–250 °C and 350–450 °C in the BFO doped samples giving rise to temperature-insensitive dielectric constant over a broad temperature span. The composition (x = 0.05) showed a permittivity of ~4000 at 100 kHz at 250 °C with a normalized permittivity Δe/e250 varying not more than± 15% from 200 °C to beyond 500 °C. In addition, the same composition yields a TCe value as low as −194 ppm/°C which is promising from the application point of view. Analysis of P-E, J-E and S-E loops predict a probable destabilization of the ferroelectric phase by introduction of relaxor state with the incorporation of BFO in the complex perovskite solid solution. Based on the current results, the NBT-ST-BFO ceramics can be designed to minimize loss via compositional engineering for high-temperature capacitor applications.