Structure, dielectric and piezoelectric properties of K0.5Na0.5NbO3–Bi0.5(Na0.7K0.2Li0.1)0.5TiO3 ceramics

(1−x)K0.5Na0.5NbO3−xBi0.5(Na0.7K0.2Li0.1)0.5TiO3+1 mol% MnO2 lead-free ceramics were prepared by an ordinary sintering method and their structure, dielectric and piezoelectric properties were investigated. A K0.5Na0.5NbO3-based solid solution with perovskite structure is formed after the addition of Bi0.5(Na0.7K0.2Li0.1)0.5TiO3 to K0.5Na0.5NbO3. A small amount of Bi0.5(Na0.7K0.2Li0.1)0.5TiO3 retards the grain growth, induces a diffuse phase transition at TC, decreases Curie temperature and weakens the ferroelectricity of the ceramics. The ferroelectric orthorhombic-ferroelectric tetragonal phase at TO–T is shifted to low temperature after the addition of (Na0.7K0.2Li0.1)0.5TiO3, leading to the formation of the coexistence of orthorhombic and tetragonal phases near room temperature at 0.015

► New KNN-based lead-free materials were developed.
► Coexistence of orthorhombic and tetragonal phases is formed at 0.015► A diffuse phase transition is induced by Bi0.5(Na0.7K0.2Li0.1)0.5TiO3.
► Enhanced piezoelectricity of d33∼183 pC/N is obtained in the ceramic with x=0.03.