A new feature of the reduction-diffusion process applied for the synthesis of magnetocaloric LaFe_(13-x)Si_x compounds

摘要

The feasibility of a powder metallurgical route based on the reduction-diffusion (R/D) process to synthesize La_(13-x)Si_x magnetocaloric compounds is shown. The reaction products, characterized via scanning electron microscopy and X-ray diffraction, show large amounts of the La_(13-x)Si_x main phase and lower contents of secondary non-desired phases, such as α-(Fe.Si). A remarkable increase in the Curie temperature (T_C) of the magnetocaloric phase after a lixiviation step, necessary to remove reaction by-products, was also investigated. Clear evidences of this change in T_C by interstitial modification due to in-situ hydrogenation are reported, based on hydrogen desorption experiments supported by mass-spectrome-try, X-ray diffraction and thermomagnetic characterization.