| Summary: | 碩士 === 國立中正大學 === 物理學系暨研究所 === 99 === In order to reduce costs and environmental pollution, recently, the object of magnetocaloric effect (MCE) reserch has been changed from expensive Gd-based alloy to much cheaper Mn-based alloy. In this study, the effect of different elements substitution for Mn and Sn on Mn3Sn2 alloy ribbons was studied. At first, we chose Mn3Sn2 as the master alloy and studied the effect of B and C substitution for Sn on the MCE of melt spun Mn3Sn2-xMx (M=B, C；x=0-0.5) ribbons. The results showed that Curie temperature is increased with the addition of B and C. For B substituted Mn3Sn2-xBx ribbons, with increasing the B content, the Curie temperature increases from 240 K for x=0 to 244 K for x=0.3, the ΔSM also has a slight increment from 4.07 mJ/cm3 K for x = 0 to 5.33 mJ/cm3 K for x=0.2. In Mn3Sn2-xCx ribbons, the Curie temperature increases from 240 K for x=0 to 250 K for x=0.3, meanwhile, the ΔSM increases from 4.07 mJ/cm3 K to 5.22 mJ/cm3 K with increasing the C content from x=0 to 0.3.
Furthermore, Al, Ga and Si elements, which have similar chemical properties as Sn, were selected to substitute for Sn. The results showed that all the Curie temperature and ΔSM of ribbons with Al, Ga and Si addition increases first and then decreases with the increase of Al, Ga and Si content, respectively. The optimal MCE of 6.38 mJ/cm3K appears in Mn3Sn1.8Al0.2 ribbon.
Finally, in order to increase the magnetization of Mn3Sn2 and improve the ΔSM , feromagnetic elements (Fe, Co, Ni) were added to substitute for Mn. It was found that the Curie temperature of ribbons with Fe, Co, Ni addition decreases with increasing the content of the corresponding added feromagnetic elements, while all the ΔSM increases a little with adding small amount of ferromagnetic elements, respectively. The optimal MCE of 4.59 mJ/cm3 K appears in ribbons with Fe addition.
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