Dielectric and piezoelectric properties of La2O3 doped (Bi0.5Na0.5)0.92(Ba0.8Sr0.2)0.08 TiO3 lead-free piezoelectric ceramics

Lead-free piezoelectric ceramics (Bi0.5Na0.5)0.92(Ba0.8Sr0.2)0.08 TiO3+x mol% La2O3(x = 0, 0.1, 0.3, 0.5, 0.8) were synthesized by conventional solid state reaction. The crystal structure of all compositions is mono-perovskite ascertained by XRD. The grain size decreased and diffuse phase transition behavior was more evident with the increasing amount of La2O3. The piezoelectric constant d33 and the electromechanical coupling factor kp showed the maximum value of 165 pC/N and 0.322 at 0.3% and 0.1% La2O3 addition, respectively, and rapidly decreased when La2O3 addition over 0.5%. The loss tangent tanδ linearly increased and the mechanical quality factor Qm linearly decreased with the increasing amount of La2O3.