Structural and electrical properties of Cu-doped (K0.5Na0.5)NbO3-MgTiO3 lead-free ceramics

Lead-free piezoelectric ceramics Cu-doped (1 − x)(K0.5Na0.5)NbO3-xMgTiO3 (KNN-MT) were fabricated by a conventional sintering technique. Their structural, dielectric, piezoelectric, and ferroelectric properties were investigated. Our results reveal that with the amount of MgTiO3 increasing, the main crystal structure of the ceramics is orthorhombic and a secondary phase (MgTiO3) could be detected. The microstructure shows some “stick-like” compounds in the ceramics, which is a useful additive for the KNN sintering. With Cu doping, the mechanical quality factor (Qm) of the KNN-MT ceramics is improved considerably; when x = 0.05, the Qm reaches 1204. Similar to Cu-doped pure KNN, the Cu-doped KNN-MT at x = 0.05 exhibits double hysteresis loops due to the effect of defect dipoles.