Processing and Characterization of Newly Piezoelectric (K,Na)(Nb,Ta)O₃ Ceramics

抄録

(K,Na)NbO₃ (KNN)-based ceramics have been developed as a lead-free piezoelectric materials. (K_0.5Na_0.5)NbO₃-based ceramics were synthesized by the solid state reaction method with newly developed sintering aid. K_5.4Cu_1.3Ta₁₀O₂₉ was found to be an effective additive for the improvements of sinterability and properties of KNN ceramics. Q_m reachs 1200 by doping 0.38 mol% K_5.4Cu_1.3Ta₁₀O₂₉. In order to improve electromechanical coupling factor (k_p) and dielectric constant (ε) of KNN ceramics with K_5.4Cu_1.3Ta₁₀O₂₉ sintering aid, the substitutional effect of Ta for Nb site on the electric properties were also investigated. The k_p and ε of (K_0.5Na_0.5)(Nb_0.7Ta_0.3)O₃ (KNNT70/30) with K_5.4Cu_1.3Ta₁₀O₂₉ were 0.44 and 830, respectively, respect to those of KNN ceramics (k_p:0.39, ε:290). E-field-induced strains of KNNT ceramics were also evaluated. The maximum strain of KNNT70/30 ceramics was found to show the highest value among the lead-free piezoelectric ceramics.