A study on BaTiO3 – NiFe2O4 composite; microstructure, multiferroic and magnetodielectric properties

The lead-free x NiFe₂O₄ – (1-x) BaTiO₃ (x = 0, 0.05, 0.1, 0.15) multiferroic composites were prepared via the solid-state sintering technique. Microstructure, multiferroic, and magnetodielectric properties of composites were investigated. According to the XRD data (from x = 5 to 15 wt%), the tetragonality factor (c_T/a_T) and unit cell volume of the BaTiO₃ (BTO) crystal system diminished. Based on SEM images, ferromagnetic NiFe₂O₄ (NFO) grains are uniformly dispersed in the ferroelectric BTO matrix without additional reaction in the interfaces of two phases. The highest values of dielectric (dielectric constant (ε_r) ∼ 1905 and dielectric loss factor (tan δ) ∼ 0.049) and ferroelectric properties (saturation polarization (P_S) ∼ 13 μC/cm² and remnant polarization (P_r) ∼ 10 μC/cm²) are attained for x = 5 wt% due to the lowest NFO (non-ferroelectric) concentration. Also, with increasing ferrite concentration (up to 15 wt%), the ferroelectric properties of the composites show a gradual decrease. The saturation magnetization (M_S) values rise due to increasing ferrite concentration (from 2 to 5 emu/g for x = 5 to 15 wt%). Moreover, coercivity (H_C) drops from 150 to 110 Oe. The simultaneous observation of the ferroelectric and ferromagnetic characteristic hysteresis loops confirmed the multiferroic effect for x = 5, 10, and 15 wt%. The highest magnetodielectric constant (3 %) is obtained for x = 15 wt% multiferroic composite at the applied magnetic field of 6 kOe.