Effect Of Addition Of Rare Earth/Transition Elements On The Magnetoloric Properties Of Fe-Based Amorphous Alloys

Fe based amorphous alloys as magnetic refrigeration materials have attracted the attention of many researchers due to their low cost,excellent magnetic and mechanical properties.However,Fe-based amorphous alloys have the disadvantages of low magnetic entropy change and high Curie temperature,which limit their application in the field of magnetic refrigeration.The purpose of this thesis is to adjust Curie temperature and improve the magnetocaloric properties of Fe-based amorphous alloys through adding transition metal or rare earth metal elements.The main research content includes two parts:(1)In the first work,Fe80-xMxP13C7(M=Co,Ni;x=0,5 and 10 at.%)bulk metallic glasses(BMGs)were prepared,and the effect of Co/Ni substitution for Fe on the magnetocaloric properties of Fe80P13C7 BMG has been investigated systematically.The replacement of Fe by Co/Ni leads to the increase of the Curie temperature(TC).The magnetic entropy change(ΔSM)decreases with the increasing of Ni,while it increases first and then decreases with the increasing of Co.The maximum value of ΔSM for the Fe75Co5P13C7 BMG can reach 5.21 J kg-1 K-1 at a magnetic applied field of 5 T,which is the largest value in the Fe-based amorphous alloys without any rare earth elements.The Fe75Co5P13C7 BMG with the tunable TC and enhanced ΔSM value indicate they can be good candidates for magnetic refrigerants.The tunable Curie temperature and large magnetic entropy change make the Fe75Co5P13C7 BMG promising candidates for magnetic refrigeration.(2)In the second work,Fe78M2P13C7(M=Gd,Dy,Er)amorphous alloy ribbons are prepared,and the effect of the addition of rare earth elements(Gd,Dy,Er)on the magnetocaloric properties of Fe80P13C7 amorphous alloy are investigated.The results show that the addition of rare earth element Gd,Dy and Er leads to the increases in the glass transition temperature and initial crystallization temperature of Fe80P13C7 amorphous alloy,indicating that the thermal stability increases.The Curie temperatures of Fe80P13C7,Fe78Gd2P13C7,Fe78Dy2P13C7 and Fe78Er2P13C7 amorphous alloys are 579 K,550 K,535 K and 531 K,respectively,indicating that the Curie temperatures of Fe80P13C7 amorphous alloys can be significantly reduced by the addition of rare earth element of Gd,Dy and Er.The Fe80P13C7,Fe78Gd2P13C7,Fe78Dy2P13C7,Fe78Er2P13C7 amorphous alloys exhibit the saturation magnetization of 160,155,144,139 emu/g,respectively,the maximum entropy change under a maximum applied field of 1.5 T of 2.20,1.89,1.77,1.60 J.kg-1.k-1,respectively,and the refrigeration capacity under a maximum applied field of 1.5 T of 125.6,130.9,112.3,109 J.kg-1,respectively,which indicates that the addition of 2 at.%rare earth element of Gd,Dy and Er results in the decrease in the saturation magnetization and magnetic entropy change of the Fe80P13C7 amorphous alloy.However,it should be noted that,compared with Fe80P13C7 amorphous alloy,the magnetic entropy change of Fe78Gd2P13C7 amorphous alloy decreases,but the refrigeration capacity slightly increases,which is mainly attributed to the increase of ΔTFWHM of-ΔSM-T curve of the present Fe-based amorphous alloy due to the addition of rare earth elements.