Spark Plasma Sintered La0.8Ce0.2Fe9.2Co0.6Si1.2/Fe Composites with Superior Properties for Near-Room-Temperature Magnetocaloric Applications

Abstract

La0.8Ce0.2Fe9.2Co0.6Si1.2/Fe bulk composites were fabricated via spark plasma sintering (SPS), and the effects of Fe powder content on the phase composition, microstructure, magnetic properties, mechanical properties, and thermal conductivity of the composites were investigated. The Fe powder content alters the α-Fe phase content in the composites. During SPS, atomic diffusion occurs between the Fe powder and the La0.8Ce0.2Fe9.2Co0.6Si1.2 matrix, which reduces the compositional homogeneity of the desired 1:13 phase and induces the formation of thermal decomposition (TD) structures in particles adjacent to the Fe powder. As Fe powder content increases from 0 wt% to 15 wt%, the maximum magnetic entropy change ((−ΔSM)max) of the composites decreases from 8.11 to 5.78 J∙kg−1∙K−1 under 2 T. Interestingly, the α-Fe phase significantly enhances the mechanical strength and thermal conductivity (λ) of the composites. The composite with 15 wt% Fe (S15) forms a continuous α-Fe network structure and possesses the best mechanical and thermal properties: the (σbc)max reaches 1463 MPa, and the λ at 300 K is 20 W·m−1·K−1. Owing to their balanced magnetic, mechanical, and thermal performances, the La0.8Ce0.2Fe9.2Co0.6Si1.2/Fe composites exhibit distinctive and balanced properties, making them promising candidates for near-room-temperature magnetic refrigeration applications.