Structure and electrical properties of K₀.₅Na₀.₅NbO₃-LiSbO₃lead-free piezoelectric ceramics

Abstract

Lead-free piezoelectric ceramics (1−x)K₀.₅Na ₀.₅NbO₃-xLiSbO₃have been fabricated by a conventional ceramic sintering technique. The results of x-ray diffraction suggest that Liᐩ and Sb⁵ᐩ diffuse into the K₀.₅Na₀.₅NbO₃lattices to form a solid solution with a perovskite structure. The ceramics can be well sintered at 1070–1110 ℃ . The introduction of LiSbO₃into the Na₀.₅K₀.₅NbO₃solid solution decreases slightly the paraelectric cubic-ferroelectric tetragonal phase transition temperature (Tᴄ) , but greatly shifts the ferroelectric tetragonal-ferroelectric orthorhombic phase transition (T[sub O–F]) to room temperature. Coexistence of the orthorhombic and tetragonal phases is formed at 0.05< x <0.07 at room temperature, leading to a significant enhancement of the piezoelectric properties. For the ceramic with x=0.06, the piezoelectric properties become optimum: piezoelectric constant d₃₃=212 pC/N, planar and thickness electromechanical coupling factors kP =46% and kt=47%, respectively, remanent polarization Pᵣ=15.0 μC/cm², coercive field Ec=1.74 kV/mm, and Curie temperature Tᴄ=358 °C.