Multifunctional properties of Mn and Fe co-doped lead-free BCT perovskite ceramics synthesized via solid-state combustion

There is a growing demand to improve the performance of multiferroic lead-free ceramics. Good ferroelectric and magnetic properties are key parameters for achieving high magnetoelectric coupling (ME). In this work, Mn and Fe were co-doped into lead-free Ba_0.96Ca_0.04Ti_(1-x)(Mn_0.5Fe_0.5)_xO₃ (BCT-xMF) ceramics with 0 ≤ x ≤ 0.030 mol%, synthesized by the solid-state combustion technique. X-ray diffraction (XRD) analysis and Rietveld refinement confirmed the formation of a pure phase with coexisting tetragonal and cubic phases in all compositions. As the Mn/Fe content increased, the percentage of the tetragonal phase decreased while the cubic phase increased, consistent with Raman spectroscopy results. Increasing Mn/Fe content also led to more oxygen vacancies and defects, and a decrease in average grain size. Analysis of the temperature-dependent dielectric constant revealed a reduction in the Curie temperature from 116 to 67 °C, corresponding to the tetragonal-to-cubic phase transformation. The ceramic with x = 0.015 showed the highest dielectric constant at the Curie temperature (ε_c), maximum saturated polarization (P_s), remnant polarization (P_r), saturation magnetization (M_s), and remnant magnetization (M_r), with values of 4583, 14.09 μC/cm², 9.31 μC/cm², 0.0127 emu/g, and 0.006 emu/g, respectively. These results indicate that Fe/Mn co-doping into BCT ceramics enhanced both ferroelectric and ferromagnetic properties, resulting in a high magnetoelectric coefficient (α_ME∼1.27 mV/cm Oe) at room temperature, making these ceramics candidates for multiferroic applications.