High temperature lead-free relaxor ferroelectric: Intergrowth Aurivillius phase BaBi2Nb2O9–Bi4Ti3O12 ceramics

Intergrowth BaBi2Nb2O9–Bi4Ti3O12 (BaBi6Ti3Nb2O21) Aurivillius phase ceramic has been found to be a relaxor ferroelectric (RFE) with the highest reported temperature of the maximum of the dielectric permittivity (Tm) of all of the known RFE systems. Dielectric characterization revealed that it has two dielectric anomalies. The first one is a frequency independent broad dielectric constant peak at ∼280 °C, while the second anomaly shows relaxor behavior at 636 °C (100 kHz). There is obvious frequency dispersion of dielectric response at room temperature, which is in agreement with dielectric properties of a typical relaxor. Ferroelectric hysteresis loops and a measurable value of piezoelectric constant d33 confirmed the ferroelectric nature of BaBi6Ti3Nb2O21 ceramics. The piezoelectric response remained even after annealing at temperatures above 636 °C.