Mass production of magnetocaloric LaFeMnSiB alloys with hydrogenation

LaFen11.39 Mn0.35 Si1.26 B0.1 Hx alloys were prepared by hydrogenation. Samples were annealed at 1343 K for 30−90 h to form the NaZn13 phase. La-rich and α-Fe secondary phases were also detected. Saturated hydrogenation at 553 K and 0.15 MPa of H2 pressure for 5 h was employed to improve the Curie temperature of the alloys to 279 K. The maximum magnetic entropy change, relative cooling power, and adiabatic temperature change of LaFe11.39 Mn0.35 Si1.26 B0.1 Hx annealed at 1343 K for 90 h after hydrogen absorption are 6.38 J/(kg · K) (magnetic changes μ0 ΔH = 1.65 T), 100.1 J/kg (μ0 ΔH = 1.65 T), and 2.2 K (μ0 ΔH = 1.48 T), respectively. Although the maximum magnetic entropy change of the LaFe11.39 Mn0.35-Si1.26 B0.1 Hx alloys is lower than those of similar alloys with high purity raw materials, the relative cooling power is nearly the same. The effect of impurities of the raw materials used was also discussed. It is assumed that the impurity of 0.2 wt. % Al is responsible for the reduced entropy change of the resulted alloys. The LaFe11.39 Mn0.35 Si1.26 B0.1 Hx alloys prepared by this method could be a low cost alternative material for room temperature magnetic cooling applications.