Convenient, low energy routes to hexagonal ferrites MFe12O19(M=Sr, Ba) from SHS reactions of iron, iron oxide and MO2 in air

Abstract

Thermal initiation of a mix of metal superoxide (MO₂ , M=Sr, Ba), iron and iron powder in air induces a self propagating reaction with velocity 0.5 mm s^–1 and the formation of predominantly MFe₁₂O₁₉ . Heating the mixture to 1150 °C for 2 h produces pure crystalline MFe₁₂O₁₉ . The ferrites were characterised by X-ray powder diffraction (Rietveld analysis), FTIR, VSM magnetism, EDAX/SEM, electron probe analysis and Mössbauer spectroscopy. The ferrites showed good purity, coercivity, remanence and hysteresis loops compared to commercial samples. Preparation of ferrite solid solutions M_xM′_yFe₁₂O₁₉ (M=Sr, Ba, Pb) was investigated.