Structural and electrical properties of Zr-doped K0.48Na0.52NbO3 ceramics: "Hard" lead-free piezoelectric

The structural and electrical properties of K0.48Na0.52Nb1-xZrxO3-delta (x = 0-0.04) ceramics prepared by the conventional solid-state reaction method were studied. Pellets with composition x <= 0.03 sintered at 1125 degrees C for 2 h showed single-phase of potassium sodium niobate (KNN) perovskite structure. Based on X-ray diffraction and Raman results, a mixture of orthorhombic and monoclinic phases was observed in intermediate compositions. The addition of Zr improved the sinterability and the "hard" piezoelectric properties of KNN, increasing the E-c and Q(m) values. The composition with x = 0.03 presented the highest permittivity at room temperature, epsilon(r)' = 363 and the lowest dielectric losses, tan delta = 0.027. Moreover, it was the sample with the highest Q(m) and d(33) values, with Q(m) = 1781 and d(33) = 82 pC/N. It was therefore the best compositions to obtain a "hard" piezoelectric material based on Zr-doped KNN, which makes it promising candidate for use as "hard" lead-free piezoelectric material for high power applications.