Tantalum influence on physical properties of (K0.5Na0.5)(Nb1−xTax)O3 ceramics

Abstract Lead-free (K 0.5 Na 0.5 )(Nb 1− x Ta x )O 3 ceramics with x  = 0.00–0.30 were prepared by the solid-state reaction technique. The effects of Ta on microstructure, crystallographic structure, phase transition and piezoelectric properties have been investigated. It has been shown that the substitution of Ta decreases Curie temperature T C and orthorhombic–tetragonal phase transition temperature T O–T , while increasing the rhombohedral–orthorhombic phase transition temperature T R–O . In addition, piezoelectric activity is enhanced with the increase of Ta content. The ceramics with x  = 0.30 have the high value of piezoelectric coefficient d 33  = 205 pC/N. Moreover, k p shows little temperature dependence between −75° C and 75 °C, and d 33 exhibits very good thermal stability over the range from −196 °C to 75 °C in the aging test.