SYNTHESIS OF BARIUM FERRITE ULTRAFINE PARTICLES BY A HYDROTHERMAL METHOD

Barium ferrite ultrafine particles were synthesized hydrothermally from aqueous mixed solutions of ferric nitrate and barium nitrate. The effect of the reaction conditions on the size of hexagonal platelike particles was investigated. As the hydrothermal temperature rises, the particle size increases. This may be because at higher temperatures and higher pressures, the particle growth rate increases. The mean size of the particles decreases with increasing stirring speed. As the alkali molar ratio defined by [OH-]/[NO3-] increases, the mean size of the particles decreases. Ultrafine particles of less than 0.1-mu-m, which are suitable for perpendicular magnetic recording media, can be synthesized by hydrothermal treatment under the conditions of temperature of 300-degrees-C, alkali molar ratio of 6, and stirring speed of 300 rpm.