Feasibility of Nd Substitution in (La, Nd)(Fe, Si)13Magnetocaloric Compound Obtained by the Reduction-Diffusion Process

Abstract

Quaternary magnetocaloric compound La1- x Nd x Fe11.3Si1.7 was synthesized via the so-called reduction-diffusion (RD) process. The RD process was carried out at 1423 K, using Ca as the reducing agent and La and Nd oxides as the precursors to form, together with iron and silicon powder, the desired cubic NaZn13-type structure. The main purpose was to study the interchange of La and Nd in terms of process yield, crystal structure parameters and typical magnetic transition temperature [Curie temperature ( $Tc$ )] associated with the magnetocaloric effect. Microstructural characterization by scanning electron microscopy associated with microprobe energy dispersive spectroscopy and backscattered electron imaging was used to identify morphology and particle size of reaction products, as well as the extent of diffusion reactions. Structural characterization results obtained by X-ray diffraction technique associated with Rietveld refinements show the possibility to obtain almost single-phase La1- x Nd x Fe11.3Si1.7, for which $x$ was varied from 0 to 0.5, with reminiscent $\alpha $ -iron phase below 10 wt%. Moreover, the $Tc$ of all obtained alloys were inferred from differential scanning calorimetry curves, showing that Nd is an effective alloying element to tune the working temperature in the near-room-temperature magnetic refrigeration.