Phase Transition and Electrical Properties of Ba0.7Ca0.3TiO3–BiFeO3 Ceramics

Abstract

Lead‐free piezoelectric ceramics of (1 − x)Ba0.70 Ca0.30TiO3–xBiFeO3 [(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 pseudocubic 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°C to 50°C, 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 ferroelectricity enhances slightly and reaches the maximum near x = 0.05, and then weakens with increasing x. On the other hand, the piezoelectric coefficient (d33) and electromechanical coupling coefficient (kp) decrease simultaneously with increasing x, whereas the mechanical quality factor (Qm) reaches the maximum near x = 0.05. The structure‐property relationship is discussed intensively. Our results may be helpful for further understanding and designing BaTiO3‐related lead‐free ferroelectric/piezoelectric materials.