Processing of nano-structured barium hexaferrite by self-propagating high temperature synthesis (SHS) using nitrate precursor

Barium hexaferrite magnetic powder was produced by self propagating high temperature synthesis (SHS) route through putting a hot filament on top of the compact mixture of iron, iron oxide and barium nitrate powders with a Fe(total)/Ba molar ratio of 12. Morphology, particle size distribution, thermal behavior, phase evolution, chemical analysis and magnetic properties of the products were investigated by SEM, LPSA, DTA/TGA, XRD, EDS and VSM techniques, respectively. EDS analysis confirmed the presence of barium hexaferrite in as-SHS sample. An exothermic peak appeared at 814 °C in DTA/TGA traces seems to be due to the formation of barium hexaferrite. Single-phase barium hexaferrite was formed after annealing of SHS product at 1150 °C for 2 h. SEM micrograph of the sample annealed at 1150 °C for 2 h showed plate-like hexagonal particles of barium hexaferrite with mean size of 2 μm. Saturation magnetization (Ms) and coercivity (Hc) for sample annealed at 1150 °C for 2 h were obtained 66 emu/g and 192 kA/m, respectively. The microstructure of as-SHS sample after it was pressed and then sintered at 1250 °C for 3 h exhibited nano-grains of barium hexaferrite with mean diameter of 200 nm.