Optimize magnetocaloric properties and preparation efficiency of off-stoichiometric La_1.1-xCe_xFe_11.7-yMn_ySi_1.3 hydrides through systematic investigation of the 1:13 phase formation mechanism

The fully hydrogenated La_1.1-xCe_xFe_11.7-yMn_ySi_1.3 magnetocaloric materials have high magnetic entropy changes while maintaining low hysteresis loss. To significantly improve the magnetocaloric properties and preparation efficiency, the 1:13 phase transition mechanism of off-stoichiometric La_1.1-xCe_xFe_11.7-yMn_ySi_1.3 ((x,y)=(0.24, 0.16), (0.34, 0.14), (0.44, 0.10)) was studied in detail. The optimal annealing temperature increased with increasing Ce(x), and the La_0.86Ce_0.44Fe_11.4Mn_0.1Si_1.3 sample annealed at 1423 K for 18 h reached 80 vol% of the 1:13 phase, which was significantly greater than that of the sample annealed at 1373 K for 7 days (69 %). After hydrogenation, the relative cooling power of La_0.86Ce_0.44Fe_11.4Mn_0.1Si_1.3 annealed at 1423 K for 18 h increased by 40 % (−ΔS_M = 8.0 J/kgK, δ_FWHM = 12.5 K) compared with that of the sample annealed at 1373 K for 7 days. The substitution of Ce atoms was found to promote the formation of the 1:13 phase. This work not only conducted an in-depth study on the annealing mechanism of Ce and Mn multielement-substituted La-Fe-Si compounds but also greatly reduced the difficulty of preparing La-Fe-Si materials with high Ce contents, which accelerated the engineering application of this type of material.