PRODUCING OF ULTRA-FINE PARTICLES OF STRONTIUM HEXAFERRITE BY CO- PRECIPITATION METHOD IN THE PRESENCE OF AN ORGANIC BASE

摘要

Mixed aqueous solution of strontium and iron nitrates were co-precipitated using tetraethyl ammonium hydroxide at 80°C. The effects of the calcination temperature on the phase composition; particle morphology; and magnetic properties of the co-precipitated materials have been investigated. The powder X-ray diffraction patterns showed that the co-precipitated material consisted mainly of crystalline phases with particle size ranges from 20 to 30 nm. Strontium hexaferrite began to form at 650°C and was fully formed at about 750°C. The mean particle size was found to increase on increasing the calcination temperature. After calcination at 950°C, plate-like particles of strontium hexaferrite with an average particle diameter of 250 nm and thickness of 70 nm are observed. It was found that the coercivity increased rapidly on increasing the calcination temperature from 650°C to 800°C and then went through a maximum at 850°C. The maximum coercivity was as high as 6.6 kOe when the co-precipitated material was calcined at 850°C for 45 min. Increasing the temperature above 900°C decreased the coercivity markedly. The saturation magnetization increased significantly up to a calcination temperature of 850°C and then increased slowly.