Microstructure and magnetocaloric property of homogeneous La(FexSi1−x)13 compounds fabricated by laser fusion using a powder mixture of Fe and LaySiz compounds

Abstract

A highly homogeneous single-phase La(FexSi1−x)13 was obtained by the heat-treatment of a parent alloy produced by the laser fusion of a powder mixture of Fe and La-Si compounds. Rapid homogenization was promoted owing to the formation of a characteristic microstructure during laser fusion even at a high Fe concentration (e.g., x = 0.91). The selective oxidation of La during laser fusion was prevented by the reduction of oxides on the surface of Fe particles. The maximum of the magnetic entropy change (ΔSM) for the specimen heat-treated at 1323 K for 24 h was − 22 J/kg K under a magnetic field change of 1 T and the specimen heat-treated for a shorter duration of 2 h exhibited a ΔSM of − 18 J/kg K. Thus, the production of the parent alloy by the laser fusion of the powder mixture significantly decreased the heat-treatment duration for the formation of a highly homogenized La(FexSi1−x)13 compound at a high Fe concentration. Consequently, the laser fusion process followed by post-annealing is possible to selectively form fine structures made of the 1:13 phase, and such a feature will lead a way to 3D precision modeling of the regenerator-bed with using the highly homogeneous La(FexSi1−x)13.