Enhanced piezoelectric properties of (Na0.53K0.47)(Nb1−xTax)O3 ceramics by Ta substitution

The effects of Ta substitution for B-site Nb in (Na0.53K0.47)(Nb1−xTax)O3 (NKNT) ceramics were investigated in the range of x = 0–0.6. It was found that polymorphic phase transitions (PPT) were significantly influenced by Ta substitution. Transitions among orthorhombic, tetragonal, and cubic phases in sequence with temperature, TO-T and TC, respectively, decreased linearly with x. At x = 0.45, TO-T was reduced to room temperature from 182 °C at x = 0, and subsequently piezoelectric coefficient (d33) at room temperature was enhanced up to 284 pC/N from 120 pC/N at x = 0 due to the coexistence of ferroelectric orthorhombic and tetragonal NKNT phases. With x further increasing beyond x = 0.45, d33 decreased due to there being no orthorhombic but only a tetragonal NKNT phase at room temperature with TO-T below room temperature.