Effects of Ce addition and annealing on microstructure, magnetocaloric properties and phase formation kinetics of LaCeₓFe₁₁Co₀.₈Si₁.₂ alloys

Abstract

High-performance magnetocaloric materials are urgently required for near-room-temperature solid-state magnetocaloric refrigeration systems, which offer an attractive energy-efficient alternative to conventional gas-based technologies. However, the potential practical application of La-Fe-Co-Si based alloys is severely hindered by their low Curie temperature and prolonged annealing times required to form the desired NaZn₁₃-type (1:13) magnetocaloric phase. In this work, we investigate the effects of Ce addition and annealing temperature on the microstructure evolution and magnetocaloric properties of LaCeₓFe₁₁Co₀.₈Si₁.₂ alloys. The results demonstrate that increasing the Ce content leads to the refinement of the microstructure and significantly reduces the annealing time required to obtain a high fraction of the 1:13 phase (over 80.6 wt% after annealing at 1323 K within 1 day when x = 3). Furthermore, hybridization between Ce and Fe enhances the itinerant-electron metamagnetic (IEM) transition, resulting in a larger magnetic entropy change (10.91 J/kg∙K, ΔH=2 T) compared to La-Fe based systems. The combined effects of Ce addition and optimized annealing conditions offer a viable strategy to produce cost-effective magnetocaloric materials with improved performance near-room temperature, advancing the development of solid-state refrigeration applications.