Structure and piezoelectric properties of K0.5Na0.5NbO3-Bi0.5Li0.5TiO3 lead-free ceramics

Lead-free (1-x) K0.5Na0.5NbO3-xBi(0.5)Li(0.5)TiO(3) + 1 mol% MnO2 piezoelectric ceramics have been prepared by a conventional ceramic technique and their structure and piezoelectric properties have been studied. Our results reveal that Bi0.5Li0.5TiO3 diffuse into K0.5Na0.5NbO3 lattices to form a solid solution with a perovskite structure. The addition of Bi0.5Li0.5TiO3 to the K0.5Na0.5NbO3 solid solution decreases the paraelectric cubic-ferroelectric tetragonal phase transition temperature (T (C)) slightly, but shifts the ferroelectric tetragonal-ferroelectric orthorhombic phase transition temperature (T (O-T)) significantly to low temperatures. As a result, coexistence of the orthorhombic and tetragonal phases is formed at 0.01 < x < 0.03 near room temperature, leading to a significant improvement in the piezoelectric properties of the ceramics. The ceramic with x = 0.025 exhibits a relatively high T (C) (392 A degrees C) and optimum piezoelectric properties: d (33) = 191 pC/N, k (p) = 51.5% and k (t) = 45.5%. The ceramic also exhibit a good thermal stability of piezoelectric properties.