Structures and electrical properties of (Na 0.5K 0.5) NbO 3-Li(Ta 0.5Nb 0.5) O 3 lead-free piezoelectric ceramics

Solid solutions of (Na _0.5K _0.5)NbO ₃ (NKN) and Li(Ta _0.5Nb _0.5)O ₃ (LTN) were investigated as a potential candidate of lead-free piezoelectric ceramics. It was found that the Curie temperature of solid solutions increases slightly with increasing the LTN content and simultaneously the polymorphic phase transition temperature linearly decrease till below room temperature. An orthorhombic to tetragonal phase transformation at room temperature, or a morphotropic phase boundary, in NKN is induced by ∼7 at% LTN addition, where the best dielectric, piezoelectric and electromechanical properties are achieved. The 0.94NKN-0.07LTN ceramics possess a dielectric constant of 765, a loss tangent of 0.04 at 1 kHz, a piezoelectric constant d ₃₃ of 253 pC/N and an electromechanical coupling factor k _p of 48%. © Springer Science+Business Media, LLC 2008.