Ca Doping Concentration Induced Enhancement in Dielectric and Magnetic Properties of Bi_1−xCa_xFeO₃ (x = 0.2 and 0.4) Ceramics

In this study, to arrest the volatile Bi, a two-stage rapid solid-state reaction method has been adopted to prepare Bi_1−xCa_xFeO₃ (x = 0.2 and 0.4) ceramics. Rietveld refinement on x-ray diffraction data confirmed the single-phase nature of the prepared samples. Unit cell volume of hexagonal structured (space group; R3c) Bi_1−xCa_xFeO₃ decreases with the increase of Ca concentrations. Temperature-dependent (250 K to 450 K) dielectric constant measurements have been performed at different frequencies (100 kHz, 300 kHz, 500 kHz, 700 kHz, 900 kHz and 1100 kHz). The dielectric constant (ɛʹ), loss tangent (tan δ) and ac-conductivity (σ_ac) remain nearly constant for low temperatures (~250 K to ~365 K) and have shown enhancement at higher temperatures (365 K to 450 K). Higher values of ɛʹ, tan δ and σ_ac are detected in case of Bi_0.6Ca_0.4FeO₃ sample. The butterfly-like loop in capacitance versus voltage curves confirms a weak ferroelectric nature. Magnetic field-dependent magnetization supports the Ca doping induced weak ferromagnetic character and exchange bias effect in the Bi_0.6Ca_0.4FeO₃ sample. The origin of high dielectric constant and weak ferromagnetic nature is briefly discussed by considering the structural perturbations and cationic interaction in the Bi_1−xCa_xFeO₃ (x = 0.2 and 0.4) ceramics.