THE EFFECT OF B2O3 ADDITION ON THE DIRECT SINTERING OF BARIUM HEXAFERRITE

Abstract

The effect of B2O3 on the calcination and on the material and magnetic properties of the direct-sintered isotropic hard barium ferrite BaO.5.6Fe2O3 was studied in the 0-0.2 mol B2O3 addition range. The addition of 0.01 mol B2O3 as boric acid in the milling stage of the raw materials, BaCO3 and Fe2O3, resulted in the enhancement of the barium hexaferrite phase in calcinations below 1000-degrees-C. In the direct-sintering process, the optimum magnetic properties (B(r) = 2000-2300 Gauss, (J)H(C) > 2500 Oersted, (B.H)max > 1 MG.Oe) were obtained with 0.01 and 0.05 mol B2O3 addition levels in the samples sintered at 1150-degrees-C for 2-3 h, and also in 0.05 mol B2O3 samples sintered at 1200 and 1250-degrees-C for 1 h. The B2O3 addition resulted in enhancement of the magnetic properties not only by aiding densification due to liquid-phase sintering, but at temperatures above 1100-degrees-C, by increasing the magnetic moment developed in the unit cell of the material. The optimum condition in this case was found to be the 0.05 mol B2O3 addition level.