Nanoparticles of Barium Hexaferrite by Gel to Crystallite Conversion and their Magnetic Properties

摘要: A novel method for the preparation of nanoparticles barium hexaferrite is realized by gel-to-crystallite (G-C) conversion method. Here, gels Fe(OH)(3). xH(2)O, 70 < x 110, were reacted with Ba(OH)(2). 8H(2)O in ethanol/water medium at 80-95 degreesC yielding precursor, iron (III) oxy hydroxide hydrate which x-ray amorphous but crystalline electron diffraction (ED). Thermal analyses showed dehydroxylation precursor around 600 to exhibits ED spotty ring patterns. Samples heat-treated 650 are X-ray average particle size 17 nm, on recrystallization 780-930 gives monocrystallites spot patterns ED. By varying wet chemical conditions, precursors variable Fe2O3/BaO ratios could be prepared heat-treatment yield monophasic ratio ranging from 4.51 6. In hyperbarium compositions, annealing 1350 leads ordering excess anti-BR sites within Ba-O layers beta -alumina type unit cells. Nanoparticles superparamagnetic as revealed Mossbauer spectra, temperature vs. magnetization plots and absence hysteresis B-H curves. With increasing heat treatment, area under loop increases continuously, 2 52 emu/g. The ferrimagnetic state continuous because out-diffusion cation vacancies, created charge compensate hydroxyl ions, which, turn, affects Fe3+-O2--Fe3+ superexchange interactions, addition surface factors.