INVESTIGATION OF AMORPHOUS FE82P11B7 ULTRAFINE PARTICLES PRODUCED BY CHEMICAL-REDUCTION

Fe82P11B7 ultrafine amorphous particles have been prepared by the reaction of Fe(III) chloride, sodium hypophosphite and potassium borohydride in aqueous solution. X-ray diffraction and electron diffraction indicated the amorphous nature of the sample and scanning electron microscopy showed that the sample consists of nearly spherical particles with diameters from 150 to 350 nm. X-ray photoelectron spectroscopy revealed that iron, phosphorus and boron existed mainly in their elemental states. The structure relaxation and crystallization of the amorphous sample were studied by Mossbauer spectroscopy after the sample had been annealed at various temperatures. The Mossbauer spectra suggested that the sample started to crystallize at 573 K; it crystallized completely through the formation of the alpha-Fe and Fe3(P0.6B0.4) phases when the annealing temperature was raised to 673 or 773 K. When the annealing temperature is low (below 573 K), no crystalline phases can be detected but, as evidenced by the dependence of hyperfine field distribution P(H) on annealing temperature, the heat treatment did cause a significant change in the microstructure of the amorphous sample.