Piezoelectric properties and hardening behavior of K5.4Cu1.3Ta10O29-doped K0.5Na0.5NbO3 ceramics

Lead-free piezoelectric ceramics K0.5Na0.5NbO3+xmol% K5.4Cu1.3Ta10O29 have been prepared by a conventional ceramic fabrication technique. All the ceramics possess a perovskite structure with orthorhombic symmetry. Our results reveal that the addition of K5.4Cu1.3Ta10O29 is effective in improving the densification of the ceramics. Besides, after the addition of K5.4Cu1.3Ta10O29, the Curie temperature and the tetragonal-orthorhombic phase transition temperature decrease and the P‐E loop becomes constricted, in particular, for the ceramic with x=0.75. Based on the symmetry-conforming principle of point defects, it is suggested that defect dipoles are formed by the acceptor dopant ions Cu2+ and O2− vacancies along the polarization direction. As a result of the low migration rate of defects, the defect dipoles remain in the original orientation during the P‐E loop measurement and thus provide restoring forces to reverse the switched polarizations. Similarly, the defect dipoles do not response along with the po...