Structure and electrical properties of K0.5Na0.5NbO3–LiSbO3 lead-free piezoelectric ceramics

Lead-free piezoelectricceramics ( 1 − x ) K 0.5 Na 0.5 Nb O 3 – x Li Sb O 3 have been fabricated by a conventional ceramicsintering technique. The results of x-ray diffraction suggest that Li + and Sb 5 + diffuse into the K 0.5 Na 0.5 Nb O 3 lattices to form a solid solution with a perovskite structure. The ceramics can be well sintered at 1070 – 1110 ° C . The introduction of Li Sb O 3 into the Na 0.5 K 0.5 Nb O 3 solid solution decreases slightly the paraelectric cubic-ferroelectric tetragonal phase transition temperature ( T c ) , but greatly shifts the ferroelectric tetragonal-ferroelectric orthorhombic phase transition ( T 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 d 33 = 212 pC ∕ N , planar and thickness electromechanical coupling factors k P = 46 % and k t = 47 % , respectively, remanent polarization P r = 15.0 μ C ∕ cm 2 , coercive field E c = 1.74 kV ∕ mm , and Curie temperature T C = 358 ° C .