Piezoelectric properties and aging mechanism of K0.5Na0.5Nb(1−y)SbyO3 piezoceramics prepared by low temperature solvothermal method

K0.5Na0.5Nb(1−y)Sb y O3 (KNNSy, y = 0.02–0.10) piezoceramics are obtained from the corresponding powder synthesized via a relatively low temperature solvothermal method. Crystalline structures and surface morphologies of these samples are analyzed by X-ray diffraction and scanning electron microscopy. The optimal sintering temperatures of KNNSy ceramics are controlled within 980–1,050 °C. The piezoelectric properties of the KNNSy ceramics are essentially affected by orthorhombic–tetragonal polymorphic phase transition. KNNS0.06 ceramic shows the maximum piezoelectric coefficient (d 33) (134 pC/N). In addition, the aging behavior of KNNSy ceramics leads to the instability of their piezoelectric properties, which can be well explained according to defect symmetry conforming principle.