Tailoring cryogenic thermal conductivity in EuTiO₃-based magnetic refrigeration materials

As one of the core components of a magnetic refrigerator, magnetic refrigeration materials are expected to have not only a considerable magnetocaloric effect but also excellent thermal conductivity. The poor thermal conductivity of many competitive oxide-based magnetic refrigerants, exemplified by EuTiO₃-based compounds, acts as a major limitation to their practical application. Therefore, improving the thermal conductivity of magnetic refrigeration materials has become a research emphasis of magnetic refrigeration in recent years. In this work, a series of EuTiO₃ (ETO)/Cu composites with different copper additives was prepared using a solid-phase reaction method by introducing appropriate amounts of copper powder. The influence of the introduction of copper on the phase composition, microstructure, thermal conductivity, and magnetocaloric effect of the composites was systematically investigated. Unexpectedly, the thermal conductivity of the composites is enhanced by up to 260% due to copper addition, accompanied by only a 5% decrease in magnetic entropy change and refrigerating capacity. Copper additive forms localized thermal conductive networks and promotes the densification process, resulting in significantly enhanced thermal conductivity of the composites. This work demonstrates the feasibility of improving the thermal conductivity of oxide-based magnetic refrigeration materials by introducing highly thermally conductive substances.