Optimize magnetocaloric properties and preparation efficiency of off-stoichiometric La1.1-xCexFe11.7-yMnySi1.3 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.