Enhanced torsional actuation and stress coupling in Mn-modified 0.93(Na_0.5Bi_0.5TiO₃)-0.07BaTiO₃ lead-free piezoceramic system

This paper is concerned with the development of a piezoelectric d₁₅ shear-induced torsion actuator made of a lead-free piezoceramic material exhibiting giant piezoelectric shear stress coefficient (e₁₅) and piezoelectric transverse shear actuation force comparable to that of lead-based shear-mode piezoceramics. The Mn-modified 0.93(Na_0.5Bi_0.5TiO₃)-0.07BaTiO₃ (NBT-BT-Mn) composition exhibited excellent properties as a torsional transducer with piezoelectric shear stress coefficient on the order of 11.6 C m^–2. The torsional transducer, consisting of two oppositely polarized NBT-BT-Mn d₁₅ mode piezoceramic shear patches, provided a rate of twist of 0.08 mm m^–1 V^–1 under quasi-static 150 V drive. The high value of piezoelectric shear d₁₅ coefficient in NBT-BT-Mn sample further demonstrated its potential in practical applications. These results confirm that the lead-free piezoceramics can be as effective as their lead-based counterparts.