Microwave-induced combustion synthesis of Li0.5Fe2.5−xAlxO4 powder and their characterization

Li0.5Fe2.5−xAlxO4 (0 ≦ x ≦ 1.0) powders with small and uniformly sized particles were successfully synthesized by microwave-induced combustion, using lithium nitrate, iron nitrate, aluminium nitrate, and carbohydrazide as the starting materials. The process takes only a few minutes to obtain as-received Al-substituted lithium ferrite powders. The resultant powders annealed at 650 °C for 2 h and were investigated by thermogravimeter/differential thermal analyzer (TG/DTA), X-ray diffractometer (XRD), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), and thermomagnetic analysis (TMA). The results revealed that the lattice constant, powder density, and crystallite size decrease linearly with the increasing of Al content in Li0.5Fe2.5−xAlxO4 samples. Moreover, the magnetic properties of Al-substituted lithium ferrite also strongly affected by Al content. The saturation magnetization, remanent magnetization, Curie temperature, and coercive force decrease significantly with the increasing of Al content.