Dielectric behaviour of MgFe_2O_4 prepared from chemically beneficiated iron ore rejects

摘要

Chemically beneficiated high silica/alumina iron ore rejects (27-76 percent Fe_2O_3) were used to synthesize iron oxides of purity 96-98 percent with SiO_2/Al_2O_3 ratio reduced to 0.03. The major impurities on chemical beneficiations were Al, Si, and Mn in the range 2-3 percent. A 99.73 percent purity Fe_2O_3 was also prepared by solvent extraction method using methyl isobutyl ketone (MIBK) from the acid extracts of the ore rejects. The magnesium ferrite, MgFe_2O_4, prepared from these synthetic iron oxides showed high resistivity of approx 10~8 ohm cm. All ferrites showed saturation magnetization, 4#pi#M_s, in the narrow range of 900-1200 Gauss and the Curie temperature, T_c, of all these fell within a small limit of 670 +- 30 K. All ferrites had low dielectric constants (#epsilon#'), 12-15, and low dielectric loss, tan #delta#, which decreased with the increase in frequency indicating a normal dielectric dispersion found in ferrites. The presence of insignificant amount of polarizable Fe~(2+) ions can be attributed to their high resistances and low dielectric constants. Impurities inherent in the samples had no marked influence on the electrical properties of the ferrites prepared from the iron ore rejects, suggesting the possibility of formation of ferrite of constant composition, MgFe_2O_4, of low magnetic and dielectric losses at lower temperatures of 1000 deg C by ceramic technique.