Mass production of magnetocaloric LaFeMnSiB alloys with hydrogenation

LaFe11.39 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 andα-Fe secondary phases were also detected.Saturated hy-drogenation at 553 K and 0.15 MPa of H2 pressure for 5 h was employed to improve the Curie tempera-ture 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 changesμ0ΔH=1.65 T), 100.1 J/kg (μ0ΔH=1.65 T), and 2.2 K (μ0ΔH=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 cool-ing 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.