Tungsten Donor Substitution and Oxygen Vacancy Modulation in Bismuth Titanate-Tantalate (Bi₃TiTaO₉) for Enhanced High-Temperature Piezoelectric Properties and Resistivity

High-temperature piezoelectric ceramics with excellent piezoelectric properties and temperature stability are crucial for advancing high-temperature piezoelectric sensor applications. However, challenges such as relatively low piezoelectric responses and increased conductivity at elevated temperatures persist. In this study, we enhanced the piezoelectric and electrical properties of bismuth titanate-tantalate (Bi3TiTaO9) ceramics by introducing tungsten as a donor substitution. The Bi3Ti1–xWxTaO9 (abbreviated as BTT–100xW) ceramics were synthesized via a conventional solid-solution method. The substitution of tungsten induces tetragonal distortion and reduces the pinning effect on the domain wall, resulting in a significant enhancement of the piezoelectric performance. Specifically, BTT–3W exhibits a high piezoelectric constant (d33 = 15.3 pC/N) and an elevated Curie temperature (TC = 883 °C). Furthermore, BTT–3W demonstrates excellent thermal stability of its electromechanical coupling properties up to 650 °C. The dielectric and electrical properties of BTT–100xW ceramics were further investigated through frequency- and temperature-dependent dielectric/impedance spectroscopy. The reduced dielectric loss and changes in the conduction mechanisms suggest that a decrease in the concentration of oxygen vacancies is primarily responsible for the reduced conductivity at high temperatures. This study highlights the role of oxygen vacancy defects in tailoring the physical properties of BTT-based ceramics, making them promising candidates for high-temperature piezoelectric applications.