Modification of magneto-caloric effect in spherical La-Fe-Co-Si compounds particles by hydrogen permeation

Abstract

The spherical La-Fe-Co-Si compound particles with giant magneto-caloric properties prepared by plasma rotating electrode process (PREP) and hydrogen permeation were obtained and their mechanism was investigated in this paper. Compared with the alloys prepared by the traditional melting and casting methods, the spherical particles prepared by the PREP have a uniform and refined structure and benefit to form the NaZn 13 -type phase with giant magneto-caloric effect (MCE). The magnetic properties of spherical particles with three different sizes show that the particles with size between 450 µm and 600 µm had the best magneto-caloric properties, the isothermal magnetic entropy change can reach 12.67 J·kg −1 ·K −1 , corresponding to the applied magnetic field changes of 0 −1.5 T. Hydrogen permeation can increase the Curie temperature ( T c ) of spherical particles, which can be ascribed to the magneto-volume effect caused by change in cell volume. When the hydrogen permeation pressure is 100 Pa, the T c increases from 218 K to 224 K, and the structure of the spherical particles remains stable at this time. The spherical La-Fe-Co-Si compound particles with giant MCE and excellent heat exchange ability are promising materials for commercial applications of magnetic refrigeration technology. • The spherical LaFe 11.3 Co 0.2 Si 1.5 alloy prepared by the plasma rotating electrode process has a uniform and fine structure. • The spherical particles can completely form NaZn 13 -type phase after heat treatment at 1373K for 120h. • Adjusting the appropriate hydrogen permeation pressure can keep the structure stable and increase the Curie temperature.