Effect of sintering temperature on the structure and magnetic properties of SmCo5/Fe nanocomposite magnets prepared by spark plasma sintering

Highly dense SmCo5/Fe nanocomposite bulk magnets were prepared by spark plasma sintering of magnetic field-milled SmCo5/Fe nanocrsytalline powders. The sintering experiments were conducted with varying temperatures of 973-1123 K. The resultant bulk materials had densities of 85-98% and mean grain sizes of 17-30 nm. The SEM analysis showed that the bulk samples prepared at higher sintering temperature exhibited dense and uniform microstructure. The XRD studies in complement with energy dispersive x-ray analysis revealed that the bulk magnets sintered at or above 1073 K exhibited Sm(Co,Fe)5 as main phase, along with other secondary phases such as Sm2(Co,Fe)17 and α-Fe(Co). A single-phase behavior with high remanence ratios (0.67-0.77) for the nanocomposite magnets was demonstrated by the magnetic measurements. In the present study, the sintering temperature of 1073 K was found to be optimum in achieving relatively high coercivity (8.2 kOe), magnetization (97.5 emu/g) and energy product (69.6 kJ/m3) for the SmCo5/Fe nanocomposite bulk magnets.