Piezoelectric properties of (K{sub 0.5}Na{sub 0.5})(Nb{sub 1-x}Ta{sub x})O{sub 3}-K{sub 5.4}CuTa{sub 10}O{sub 29} ceramics

(K{sub 0.5}Na{sub 0.5})(Nb{sub 1-x}Ta{sub x})O{sub 3} (KNNT)-based ceramics have been synthesized via a solid-state reaction. In this study, KNNT-based ceramics were sintered at atmospheric pressure by adding small amounts of sintering aid [0.38 mol % K{sub 5.4}Cu{sub 1.3}Ta{sub 10}O{sub 29}]. The (K{sub 0.5}Na{sub 0.5})NbO{sub 3} (KNN) ceramics which synthesized by using the K{sub 5.4}Cu{sub 1.3}Ta{sub 10}O{sub 29} showed 'hard' piezoelectric characteristics such as a high mechanical quality factor (Q{sub m}=1300) and low tan {delta} (0.4%). The quantitative effects of Ta on the electrical properties of (K{sub 0.5}Na{sub 0.5})(Nb{sub 1-x}Ta{sub x})O{sub 3}-K{sub 5.4}Cu{sub 1.3}Ta{sub 10}O{sub 29} ceramics were also examined. Ta substitution provides 'soft' piezoelectric characteristics and a large electrostrictive effect for KNN, which resulted in an improvement in k{sub p}, {epsilon}{sub r}, strain, and d{sub 33} of KNNT ceramics depending upon the Ta content. Especially (K{sub 0.5}Na{sub 0.5})(Nb{sub 0.7}Ta{sub 0.3})O{sub 3} showed the maximum strain and d{sub 33} values of 0.11% (at 40 kV/cm) and 270 pm/V (at 30-40 kV/cm), respectively. This strain level is comparable to that of hard Pb(Zr,Ti)O{sub 3} ceramics.