Synthesis and characterization of lead-free 0.5Ba(Zr_0.2Ti_0.8)O₃-0.5(Ba_0.7Ca_0.3)TiO₃ ceramic

Polycrystalline sample of lead-free 0.5Ba(Zr_0.2Ti_0.8)O₃-0.5(Ba_0.7Ca_0.3)TiO₃ ceramic has been synthesized by solid state reaction method. Single-phase perovskite structure with rhombohedral symmetry was confirmed by x-ray diffraction. Temperature dependent dielectric permittivity studies demonstrated frequency independent behavior, indicating that the studied sample was not a typical relaxor ferroelectric. A polymorphic phase transition between rhombohedral and tetragonal phase was noticed near room temperature followed by a tetragonal to cubic transition with 97 °C as the temperature of maximum permittivity. The macroscopic values of d₃₃ and d₃₁ were ∼350 pC/N and −141 pm/V, whereas the electromechanical coupling factors k_p and k_t were 44.5% and 41.6%, respectively. Bulk P-E hysteresis loop was obtained with saturation polarization 11 μC/cm² and coercive field ∼4 kV/cm. Distinct polarization contrast with a complex mosaic-like domain structure was observed in the out-of-plane mode of piezoresponse force microscopy. The domain width and the correlation length were estimated to be nearly 2 μm and 827 nm, respectively. Local hysteresis loop with apparent coercive voltage, V_c = 15.8 V, was observed.