The doping effects of BiFe_1-xCo_xO₃ (x=0.0-0.8) in layered perovskite Bi₄Ti₃O₁₂ ceramics

Bi₅Fe_1-xCo_xTi₃O₁₅ (x= 0.0, 0.2, 0.4, 0.5, 0.6, and 0.8) multiferroic ceramics are synthesized in two steps using the solid state reaction technique. X-ray diffraction patterns show that the samples have four-layer Aurivillius phases. At room temperature (RT), the samples each present a remarkable coexistence of ferromagnetism (FM) and ferroelectricity (FE). The remnant polarization (2P_r) reaches its greatest value of 14 μC/cm² at x = 0.6. Remnant magnetization (2M_r) first increases and then decreases, and the greatest 2M_r is 7.8 menu/g when x= 0.5. The magnetic properties for x = 0.4 are similar to those for x= 0.6, indicating that the magnetic properties originate mainly from the coupling between Fe³⁺ and Co³⁺ ions, rather than from their own magnetic moments.