Thermal stability and electrical properties of BiFe_1−xM_xO₃ (M = Al³⁺, Ga³⁺) ceramics

BiFeO₃ (BFO) is a fascinating multiferroic material, exhibiting ferroelectric and G-type antiferromagnetic characteristics simultaneously. In this work, non-magnetic Al³⁺ and Ga³⁺ doped BFO (BFAO and BFGO) ceramics were synthesized via sol–gel and conventional sintering methods. Structural, thermal stability and electrical properties of samples were analyzed in detail. X-ray diffraction (XRD) patterns of powder and ceramic samples demonstrated efficient crystallization, consisting of rhombohedral structures with R3c space group for small amounts of added dopant. Thermal analysis exhibited that BFO decomposes into Bi₂₅FeO₃₉ and Bi₂Fe₄O₉ at 950 °C. It is found that Al³⁺ and Ga³⁺ doping readily contribute to decomposition, as supported by calculations from first-principles. BiAlO₃ and BiGaO₃ are unstable and would spontaneously decompose, if they could be synthesized using ordinary technology. As a result, decomposition temperatures of doped powders decreased to ~ 680 °C. Dielectric behavior can be explained through the Maxwell–Wanger model and Koop's theory. Dielectric loss decreased with increasing substitution. Leakage current density of doped ceramics became 2–3 orders of magnitude lower than that of BFO ceramic, improving performance and championing applications of modified BFO in future.