Large electrostrain with good temperature stability in sodium niobate based ceramics

Abstract

A large electrostrain of 0.24% with a converse piezoelectric constant of 790 pm V⁻¹ was obtained from the LiSbO₃ and (Bi_0.5Na_0.5)(Zr_0.9Sn_0.1)O₃ modified KNbO₃ ceramics. The electrostrain showed good temperature stability with vibration within 3% in the range from room temperature to 200 °C. It can even rival the current working horse PZT4. Besides, the present ceramics exhibited a large d₃₃ of 207 pC N⁻¹. The enhanced piezoelectric properties were achieved by pinching the phase with different symmetries together, experimentally by doping. Here the isovalent additive LiSbO₃ was employed to lower the tetragonal to orthorhombic phase transition temperature and to raise the orthorhombic to rhombohedral phase transition temperature, i.e. pinch the three ferroelectric phases together. Meanwhile (Bi_0.5Na_0.5)(Zr_0.9Sn_0.1)O₃ was used as the aliovalent doping to lower the T_c. It consequently resulted in a decrease of polarization anisotropy between phases with different symmetries and thus led to a large piezoelectric performance.