La（Fe, Si）13-based compounds have been considered as promising candidates for magnetic refrigerants particularly near room temperature. Herein we review recent progress particularly in the study of the effects of in...La（Fe, Si）13-based compounds have been considered as promising candidates for magnetic refrigerants particularly near room temperature. Herein we review recent progress particularly in the study of the effects of interstitial H and/or C atoms on the magnetic and magnetocaloric properties of La（Fe, Si）13 compounds. By introducing H and/or C atoms, the Curie temperature Tc increases notably with the increase of lattice expansion which makes the Fe 3d band narrow and reduces the overlap of the Fe 3d wave functions. The first-order itinerant-electron metamagnetic transition is conserved and the MCE still remains high after hydrogen absorption. In contrast, the characteristic of magnetic transition varies from first-order to second-order with the increase of C concentration, which leads to remarkable reduction of thermal and magnetic hysteresis. In addition, the introduc- tion of interstitial C atoms promotes the formation of NaZnl3-type （1：13） phase in La（Fe, Si）13 compounds, and thus reducing the annealing time significantly from 40 days for LaFe11.7Sil.3 to a week for LaFell.7Sil.3C0.2. The pre-occupied interstitial C atoms may depress the rate of hydrogen absorption and release, which is favorable to the accurate control of hydrogen content. It is found that the reduction of particle size would greatly depress the hysteresis loss and improve the hydrogenation process. By the incorporation of both H and C atoms, large MCE without hysteresis loss can be obtained in La（Fe, Si）13 compounds around room temperature, for instance, La0.7Pr0.3Fe115Si15C0.2H12 exhibits a large IASM[ of 22.1 J/（kg＇K） at Tc = 321 K without hysteresis loss for a field change of 0-5 T.展开更多
基金supported by the National Natural Science Foundation of Chinathe Hi-Tech Research and Development program of China+2 种基金the Key Research Program of the Chinese Academy of Sciencesthe National Basic Research Program of Chinathe Fundamental Research Funds for the Central Universities
文摘La（Fe, Si）13-based compounds have been considered as promising candidates for magnetic refrigerants particularly near room temperature. Herein we review recent progress particularly in the study of the effects of interstitial H and/or C atoms on the magnetic and magnetocaloric properties of La（Fe, Si）13 compounds. By introducing H and/or C atoms, the Curie temperature Tc increases notably with the increase of lattice expansion which makes the Fe 3d band narrow and reduces the overlap of the Fe 3d wave functions. The first-order itinerant-electron metamagnetic transition is conserved and the MCE still remains high after hydrogen absorption. In contrast, the characteristic of magnetic transition varies from first-order to second-order with the increase of C concentration, which leads to remarkable reduction of thermal and magnetic hysteresis. In addition, the introduc- tion of interstitial C atoms promotes the formation of NaZnl3-type （1：13） phase in La（Fe, Si）13 compounds, and thus reducing the annealing time significantly from 40 days for LaFe11.7Sil.3 to a week for LaFell.7Sil.3C0.2. The pre-occupied interstitial C atoms may depress the rate of hydrogen absorption and release, which is favorable to the accurate control of hydrogen content. It is found that the reduction of particle size would greatly depress the hysteresis loss and improve the hydrogenation process. By the incorporation of both H and C atoms, large MCE without hysteresis loss can be obtained in La（Fe, Si）13 compounds around room temperature, for instance, La0.7Pr0.3Fe115Si15C0.2H12 exhibits a large IASM[ of 22.1 J/（kg＇K） at Tc = 321 K without hysteresis loss for a field change of 0-5 T.
