Microstructure, dielectric and ferroelectric properties of 0.97[(Na0.5Bi0.5)1−1.5xLax]TiO3-0.03BaTiO3 lead-free ceramics

Lead-free ceramics, 0.97[(Na0.5Bi0.5)1−1.5xLax]TiO3-0.03BaTiO3 (NBTB-xLa, x = 0, 0.01, 0.02, 0.03, 0.05 and 0.08), were prepared by using a conventional solid state reaction method. The ceramics with x ⩽ 0.05 have pure perovskite, while a secondary phase appears in the sample with x = 0.08. The doping of La3+ decreases grain size of the ceramics. For both the unpoled and poled NBTB-xLa ceramics, there exist two dielectric anomalies. For the poled ceramics with x = 0, 0.01, 0.02 and 0.03, a new dielectric anomaly appears at depolarization temperature (Td). The Td peak is not observed in the εr-T curves for the ceramics with x = 0.05 and 0.08. The phase transition temperature (Tm) increases with increasing amount of La3+, but the values of Td and maximum dielectric constant (εm) decrease gradually. Piezoelectric constants (d33) of the ceramics with x = 0, 0.01, 0.02, 0.03, 0.05 and 0.08 are 91, 87, 77, 56, 7 and 2 pC/N, respectively. The change in ferroelectric properties of the samples with increasing content of La3+ is also discussed.