Research On The Synthesis And Magnetic Properties Of Nd₆Fe₁₃Pd Based Alloy

With the development of society and times,traditional refrigeration technology cannot meet people’s needs for energy conservation and environmental protection,so seeking a new type of refrigeration technology is one of the hotspots at present.The magnetocaloric technology based on the magnetocaloric effect has become a new type of refrigeration technology that is expected to replace traditional refrigeration due to its high refrigeration efficiency and environmental friendliness.Finding magnetic materials with high magnetocaloric performance has become a top priority for research now.The compound Nd₆Fe₁₃Pd is most likely to become a new generation of magnetocaloric materials due to its rich magnetic phase transition and potential"table-like"magnetocaloric effect.This paper prepared alloy system samples using the arc melting method,and doped and substituted Nd,Fe,and Pd positions to study their crystal structure,magnetic transition,and magnetocaloric performance.The main research results are as follows:（1）Preparation of series samples with nominal composition of Nd_6-xRE_xFe₁₃Pd（RE=Gd,Tb,Dy;x=0.3,0.6,0.9）was conducted.XRD patterns showed that the crystal structure of all samples was the tetragonal Nd₆Fe₁₃Si structure,and the space group was I4/mcm.Combined with EDS spectra results,the maximum solid solubility of Gd,Tb,and Dy in the parent phase Nd₆Fe₁₃Pd was determined to be 4.5 at%,3.0 at%,and 3.0 at%,respectively.Magnetic measurements showed that all samples were in the ferromagnetic（FM）state at low temperatures,and a magnetic phase transition from（FM）to antiferromagnetic（AFM）occurred as the temperature increased.Compared with the parent phase Nd₆Fe₁₃Pd,the transition temperature of samples doped with different heavy rare earths（Gd,Tb,Dy）was improved,especially for the sample Nd_5.1Gd_0.9Fe₁₃Pd,whose transition temperature was close to room temperature（277 K）.The maximum magnetic entropy changes of samples Nd_5.1Gd_0.9Fe₁₃Pd,Nd_5.4Tb_0.6Fe₁₃Pd,and Nd_5.4Dy_0.6Fe₁₃Pd were 2.2 J kg^-1 K^-1,3.4 J kg^-1 K^-1,and 2.6 J kg^-1 K^-1,respectively,and their refrigeration capacities（RC）were 169 J kg^-1,200J kg^-1,and 167 J kg^-1,respectively.The higher transition temperature and larger refrigeration capacity indicate the potential of series samples Nd_6-xRE_xFe₁₃Pd（RE=Gd,Tb,Dy;x=0.3,0.6,0.9）to become room temperature magnetic refrigeration materials.（2）A series of samples Nd₆Fe₁₃Pd_1-xAu_x（x=0.1～1.0）were prepared,and the Rietveld refinement results showed that all samples had a tetragonal Nd₆Fe₁₃Si-type structure with space group I4/mcm.According to the results of magnetic measurement,it was found that when the Au content x≤0.4,the series of samples Nd₆Fe₁₃Pd_1-xAu_x（x=0.1～0.4）underwent a continuous magnetic phase transition from ferromagnetic to antiferromagnetic to paramagnetic with increasing temperature.When the Au content x≥0.5,the magnetic ground state of the sample Nd₆Fe₁₃Pd_1-xAu_x（x=0.5～1.0）at low temperatures was antiferromagnetic,and only the AFM-PM magnetic transition occurred with increasing temperature.With the increase of Au content,the Neel temperature of the series of samples gradually increased.The introduction of Au resulted in a"table-like"magnetic entropy change,greatly improving the cooling efficiency and cooling capacity.（3）The effects of Mn,Co and Ni on the crystal structure and magnetocaloric properties of Nd₆Fe₁₃Pd were studied.The Rietveld refinement results show that the structure of the series samples is tetragonal Nd₆Fe₁₃Si type,with space group I4/mcm.The magnetic property test results of the samples show that Mn,Co,and Ni will not change the magnetic phase transition type of the compound Nd₆Fe₁₃Pd but will reduce its FM-AFM transition temperature.Among them,the magnetic transition temperature of sample Nd₆Fe_12.5Mn_0.5Pd is the lowest,which is 142 K.The magnetic entropy changes of Nd₆Fe_12.9Mn_0.1Pd,Nd₆Fe_12.5Mn_0.5Pd,Nd₆Fe_12.9Co_0.1Pd and Nd₆Fe_12.9Ni_0.1Pd are 4.5 J kg^-1 K^-1,4.4 J kg^-1 K^-1,4.3J kg^-1 K^-1 and 4.6 J kg^-1 K^-1,respectively.The corresponding RC values are 188 J kg^-1,172 J kg^-1,192 J kg^-1 and 223 J kg^-1,respectively.At the same time,compared with the parent phase,Mn,Co,Ni doping broadens its working temperature range and increases the refrigeration capacity of the sample,indicating that the series of samples Nd₆Fe_13-xM_xPd（M=Mn,Co,Ni;x=0.1,0.5）have the potential to be a new generation of magnetic refrigeration materials.