Improvement of the strontium ferrite coercivity in using nano-structured and submicron-sized SrFe_(12)O_(19) powders

摘要

The crystal structure and magnetic properties of SrFe_(12)O_(19) powders prepared by two methods were investigated. One of them consists in the milling of SrFe_(12)O_(19) followed by its high temperature aging. The milling leads to a decrease in the size of crystallites and an increase in the lattice microstrains. The subsequent high temperature aging increases the coercivity up to 5 kOe owing to the formation of nanocrystalline structure. The preliminarily annealing of milled powder in a magnetic field results in the formation of anisotropic nanostructured powder after subsequent high temperature aging. Such a powder has the possibility to be textured in a magnetic field. The second method was used to synthesize submicron-sized SrFe_(12)O_(19) particles. Glass-ceramic SrO-Fe_2O_3-B_2O_3 samples were obtained by melt-quenching and subsequent crystallization aging of the glass. The submicron-sized powder was obtained by removing the matrix phases by etching. Ferrite samples prepared by pressing of the powder and subsequent aging at 1000-1150°C have H_(ci) up to 8 kOe.