EFFECT OF MECHANICAL ACTIVATION OF REAGENTS ON SYNTHESIS OF Li-Sm FERRITE

Abstract

The effect of the energy intensity of mechanical grinding of Sm2O3(14.7 wt.%)//Fe2O3(77.5 wt.%)/Li2CO2(7.8 wt.%) powder reagents on synthesis of Li-Sm ferrite was investigated by X-ray diffraction analysis, thermogravimetry, and differential scanning calorimetry. The study used a Retsch E-max ball mill, which provides different energy intensity of mechanical grinding at different rotational speed of 300, 1000, and 1500 rpm. The interaction between the initial reagents was analyzed through heating the powder mixture to 900 °C in air in the furnace of the Netzsch STA 449C Jupiter thermal analyzer. A complete cycle of ferrite synthesis, including high temperature isothermal holding, was performed in the laboratory furnace at 900 °C for 240 min. It was found that at increased energy intensity of powder grinding, the temperature range of interaction between Sm2O3/Fe2O3/Li2CO3 shifts to lower temperatures by 200 °С, which indicates an increased reactivity of powder reagents. In this case, a two-phase composite material is formed during synthesis, which consists of unsubstituted lithium ferrite α-Li0.5Fe2.5O4 (81.0–81.8 wt.%) and SmFeO3 (18.2–19 wt.%). Within the limits of the experimental error, the concentration ratio of the synthesized phases does not depend on the energy intensity of grinding the initial reagents. Synthesis of unsubstituted lithium ferrite was confirmed by X-ray diffraction data (lattice parameter of ~0.833 nm), an endothermic peak in the differential scanning curve indicating the α-Li0.5Fe2.5O4 →β-Li0.5Fe2.5O4 transition, and by the Curie temperature (~630 °C) determined by thermogravimetry in a magnetic field. The result obtained may generate interest in the technology of ferrites of new compositions substituted with rare earth elements, which possess unique properties.