Development of electrical properties in lead-free bismuth sodium lanthanum titanate–barium titanate ceramic near the morphotropic phase boundary

The near morphotropic phase boundary (MPB) of lead-free piezoelectric ceramics based on bismuth sodium lanthanum titanate (Bi0.487Na0.487La0.017TiO3:BNLT) and barium titanate (BaTiO3:BT) was carefully investigated by a modified two step mixed-oxide method. In this case the BNLT and BT powders were produced separately using calcination temperatures of 900 °C and 1200 °C, respectively. After that they were mixed with the desired compositions of (1 − x)BNLT–xBT, where x = 0.00, 0.02, 0.04, 0.06, 0.08, and 0.10. Then the powders were pressed and subsequently sintered at various temperatures to obtain the maximum density under each condition. It was found that the BT addition has a significant effect on grain growth inhibition of the BNLT–BT ceramics and this in turn gave rise to an enhancement in dielectric constant (εr) of the corresponding ceramics. The piezoelectric coefficient (d33) was also improved greatly to about 130 pC/N in the 0.96BNLT–0.04BT ceramic sample sintered at 1125 °C. This offered an opportunity to obtain a good candidate for replacing the lead-based piezoelectrics.