Sintering and Piezoelectric Properties of Potassium Sodium Niobate Ceramics with Newly Developed Sintering Aid

As a candidate for lead-free piezoelectric materials, (K_0.5Na_0.5)NbO₃ (KNN)-based ceramics have been successfully synthesized via a solid state reaction. In this study, KNN-based ceramics were sintered under atmospheric pressure by adding the newly developed sintering aid (K_5.4Cu_1.3Ta₁₀O₂₉, KCT). The effects of KCT addition on the sinterability and electrical properties of the KNN ceramics were examined. The KCT addition to KNN at more than 0.38 mol% was effective to improve the sinterability of the KNN ceramics. The phase transition temperature of the KNN ceramics prepared indicated that part of KCT reacted with the KNN matrix during the sintering process. The ε_r, k_p, N_p and Q_m values of prepared KNN ceramics strongly depended upon the KCT content. The KCT addition to KNN greatly improved the Q_m values (>1000) of the KNN ceramics. The Q_m and k_p of 0.38 mol% KCT added KNN ceramics were 1200 and 0.42, respectively. In addition, the KNN ceramics with 0.38 mol% KCT showed large field induced strain of 0.09% at 40 kV/cm, and d₃₃ of approximately 190 pm/V under a unipolar field from 30 to 40 kV/cm.