Microstructure and Magnetocaloric Effect of Spark Plasma Sintered LaFeSi Magnets with LaAl Addition

Abstract:

Using LaFe_11.3Si_1.7 and La_0.77Al_0.23 alloys as precursors, the bulk LaFeSi samples with excellent magnetocaloric performance were synthesized through the spark plasma sintering (SPS) technology. The results show that the La_0.77Al_0.23 compound with a low melting point is helpful in facilitating peritectic reaction, and NaZn₁₃-type phase with high content can be achieved. A slight itinerant-electron-metamagnetic transition is observed. The increased thermal annealing time facilitates magnetic transition from the first order to the second order, which is ascribed to the excessive Al diffusion into the 1:13 phase. Under the thermal treatment condition of 1000 °C/6 h, the maximum entropy change (-ΔS_M) ^max of 12.40 J?kg^-1?K^-1 can be obtained, and the highest refrigerating capacity, up to 318.40 J?kg^-1, is achieved under thermal annealing condition of 1000 °C/10 h.

Key words:LaFeSi;magnetocaloric effect;microstructure