Study on the strain behavior and piezoelectric properties of lead-free Bi0.5(Na0.8K0.2)0.5TiO3 ceramics modified with Sn4+ ions

The microstructure, strain behavior, and piezoelectric properties of Bi0.5(Na0.8K0.2)0.5TiO3 (BNKT-Sn) piezoelectric ceramics modified with Sn4+ ions were systematically studied. The experimental results indicated that the Sn4+ ion doping was a viable and effective method to promote the electromechanical properties and the strain behavior of the BNKT ceramics. When the Sn content was 0.02 mol, the resultant BNKT ceramics exhibited excellent electrical properties with a density of 5.92 g.cm–3, a dielectric constant (εr) of 1235, a dielectric loss (tanδ) of 0.048, the electromechanical coupling factors of 0.36 (kp) and 0.39 (kt), a piezoelectric coefficient (d33) of 171 pC/N, and a mechanical quality factor (Qm) of 125. Moreover, a large unipolar strain of 0.45% and a high normalized strain of 865 pm/V were achieved at 50 °C. The main achievement of this study was the large normalized strain (d33*) of 876 pm/V at the SnO2 content of 0.04 mol.