Phase Transition and Electrical Properties of <scp> <scp>Ba</scp> </scp> _0.7 <scp> <scp>Ca</scp> </scp> _0.3 <scp> <scp>TiO</scp> </scp> ₃ – <scp> <scp>BiFeO</scp> </scp> ₃ Ceramics

Abstract

Lead‐free piezoelectric ceramics of (1 − x ) Ba 0.70 Ca 0.30 TiO 3 – x BiFeO 3 [(1 − x ) BCT – x BF , 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 ( 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.