A new feature of the reduction–diffusion process applied for the synthesis of magnetocaloric LaFe13−xSix compounds

The feasibility of a powder metallurgical route based on the reduction–diffusion (R/D) process to synthesize LaFe13−xSix magnetocaloric compounds is shown. The reaction products, characterized via scanning electron microscopy and X-ray diffraction, show large amounts of the LaFe13−xSix main phase and lower contents of secondary non-desired phases, such as α-(Fe,Si). A remarkable increase in the Curie temperature (TC) of the magnetocaloric phase after a lixiviation step, necessary to remove reaction by-products, was also investigated. Clear evidences of this change in TC by interstitial modification due to in-situ hydrogenation are reported, based on hydrogen desorption experiments supported by mass-spectrometry, X-ray diffraction and thermomagnetic characterization.

► Synthesis of LaFe13−xSix compounds via a calciothermic reduction–diffusion route.
► Reduced synthesis time of about 5 h, compared to 7 days of melting techniques.
► No need of extra heat treatment, in order to anneal the compounds.
► In situ hydrogenation of LaFe13−xSix during the lixiviation process.