Phase formation, microstructure, electrical and magnetic properties of 0.94Bi_0.50Na_0.50TiO₃–0.06Ba_0.85Ca_0.15Ti_0.90Zr_0.10O₃ ceramics doped with Bi₂FeCrO₆ prepared via solid-state combustion technique

Lead-free 0.94Bi_0.50Na_0.50TiO₃–0.06Ba_0.85Ca_0.15Ti_0.90Zr_0.10O₃–xmol%Bi₂FeCrO₆ ceramics, with x = 0–0.021 (BNT–BCTZ–xBFCO), were calcined at 650 °C for 2 h and sintered at 1150 °C for 2 h using the solid-state combustion technique. The effect of BFCO content (x) on the phase formation, microstructure, electrical and magnetic properties was studied. The sintered pellets exhibited a pure perovskite phase with the coexistence of rhombohedral (R3c) and tetragonal (P4bm) phases in all the studied compositions. The percentage of R3c increased as x increased from 0 to 0.013, before decreasing, as obtained from the Rietveld refinement analysis (Fullprof). A morphotropic phase boundary of BNT–BCTZ–xBFCO ceramics was observed at x = 0.013, and the ratio between the rhombohedral and tetragonal phases of this composition was 51.0:49.0. The scanning electron microscopy analysis showed polyhedral-shaped grains whose average size increased with increase in the BFCO content (x). The appropriate amount of BFCO doped into BNT–BCTZ ceramics enhanced the electrical, ferroelectric and piezoelectric properties. At optimum doping (x = 0.013), the sample exhibited the highest relative density (98.2%), a high dielectric constant (ε_R = 1572 and ε_m = 5137), maximum remanent polarization (P_r = 42.41 µC/cm²), low coercive field (E_c = 33.57 kV/cm), maximum piezoelectric coefficient (d₃₃ = 241 pC/N) and the highest normalized strain (\( d_{33}^{*} \) = S_max/E_max = 765 pm/V). These improvements to BNT–BCTZ make the ceramic a potential candidate for use in capacitors, sensors and actuators. The magnetic properties also changed with different BFCO content (x). The sample with x = 0 showed diamagnetic behavior, while the samples with 0.003 ≤ x ≤ 0.021 exhibited a paramagnetic behavior with higher magnetization at higher BFCO content.