Phase Transition and Electrical Properties of Ba_(0.7)Ca_(0.3)TiO_3-BiFeO_3 Ceramics

摘要

Lead-free piezoelectric ceramics of (1 - x)Ba_(0.70) Ca_(0.30)TiO_(3-x): BiFeO_3 1(1 - x)BCT-xBF, x = 0-0.065] have been prepared and investigated. The ceramics with x ≤ 0.06 have diphasic tetragonal and orthorhombic crystal structures, whereas tetragonal phase is suppressed by the introduction of BF. As a result, the composition with .x = 0.065 is found to have diphasic pseu-docubic and orthorhombic phases. Significantly composition-dependent grain size is observed. With increasing x from 0 to 0.065, the ferroelectric-paraelectric phase transition temperature decreases monotonically from 128℃ to 50℃, accompanied by enhanced ferroelectric relaxor behavior, as indicated by the widened diffused phase transition temperature. The room temperature polarization-electric field (P-E) hysteresis loops and strain-electric field (S-E) curves indicate that the ferro-electricity enhances slightly and reaches the maximum near x = 0.05, and then weakens with increasing x. On the other hand, the piezoelectric coefficient (d_(33)) and electromechanical coupling coefficient (k_p) decrease simultaneously with increasing x, whereas the mechanical quality factor (Q_m) reaches the maximum near x = 0.05. The structure-property relationship is discussed intensively. Our results may be helpful for further understanding and designing BaTiO_3-related lead-free ferroelectric/piezoelectric materials.