Characterization of ultra-fine amorphous particles prepared by chemical reduction

Amorphous ultra-fine particles have been prepared in the systems of FeB and FeMB (M: transition metal) by a chemical reduction method using KBH₄ in aqueous solution. The chemical composition of the FeB particles depends on the molar ratio, M_R, of KBH₄ to Fe²⁺ ions on mixing. X-ray diffraction patterns show that for M_R<9.0 the particles contain a crystalline phase that corresponds to a boron concentration of <30 at.%. The particles have an amorphous structure for values of M_R>9.0. The results of Mössbauer measurements show that the particles consist of an amorphous phase, Fe³⁺ oxide and α-Fe for M_R<10.0 and of an amorphous phase and Fe³⁺ oxide for M_R≧10.0. It is also confirmed that the distribution of hyperfine magnetic field, P(B_hf) changes with M_R.