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The structures, Curie temperature, dielectric relaxor behaviors, ferroelectricity, ferromagnetism, and magnetocapacitance of the (1− x) Ba0.70 Ca0.30 TiO3- x BiFeO3 [(1− x) BCT- x BF, x = 0-0.90] solid solutions have been systematically investigated. The ceramics have coexisted tetragonal (T) and orthorhombic (O) phases when x ≤ 0.06, coexisted pseudocubic (PC) and O phases when x = 0.065, coexisted cubic and O phases when 0.07 ≤ x ≤ 0.12, PC phase when 0.21 ≤ x ≤ 0.42, coexisted T and rhombohedral (R) phases when 0.52 ≤ x ≤ 0.70, and R phase when x ≥ 0.75. Significantly, composition-dependent microstructures and Curie temperature are observed, the average grain size increases from 1.9 μm for x = 0, reaches 12.0 μm for x = 0.67, and then decreases to 1.3 μm for x = 0.90. At room temperature, the ceramics with x = 0.42-0.70 show piezoelectric properties and multiferroic behaviors, characterized by the polarization-electric field, polarization current intensity-electric field, and magnetization-magnetic field curves, the composition with x = 0.67 has maximum polarization, remnant polarization, maximum magnetization, and remnant magnetization of 15.0 μC/cm2, 9.1 μC/cm2, 0.33 emu/g, and 0.14 emu/g, respectively. In addition, the magnetocapacitance is evidenced by the increased relative dielectric constant with increasing the applied magnetic field ( H). With Δ H = 8 kOe, the composition with x = 0.67 shows the largest values of (εr( H) − εr(0))/εr(0) = 2.96% at room temperature. The structure-property relationship is discussed intensively. [ABSTRACT FROM AUTHOR]

Lead-free piezoelectric ceramics of (1 − x) Ba0.70 Ca0.30 TiO3- x BiFeO3 [(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 ( 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. [ABSTRACT FROM AUTHOR]