Study On Preparation And Magnetocaloric Properties Of Rare Earth-Transition Metal Based Room Temperature Magnetic Refrigerant

In recent years, the traditional vapor compression technology is gradually approaching its technical limitations because of additional increases in energy efficiency, and environmental concerns. while magnetic refrigerant promises significant improvements in both of two. Magnetic refrigerant materials represent the development of new magnetic refrigeration technology as an energy efficient and environmentally safe alternative to existing vapor compression refrigeration. This paper is devoted to research the relationship between magnetocaloric effect and Curie temperature. Since the rare earth elements are with characteristics of high magnetic moment, small specific heat and high magnetization when formed compound with transition elements, It hopefully can be as room-temperature magnetic refrigerator in an efficient, low-cost magneticefrigerants. We focus on study of AB2 type rare earth-iron compounds.Firstly, CeFe2 and (Ce1_xRx)Fe2(R=Dy、Tb) alloys were prepared by vacuum melting method. The influences of annealing temperature, substitution of rare earth elements to the phase structure and magnetocaloric effect of the alloys were investigated systematically. With the phase diagram and XRD results, we can determine the appropriate annealing temperature.Through the microstructure and interaction between different magnetic atoms, g-factor, the influence of different doping rare earth elements on Curie temperature and magnetocaloric effect were investigated. The first-order phase transition and second-order phase transition characteristics were analysised, and the change of magnetic entropy in the phase transition process were studied.The results of XRD indicates that impurity phase in alloy samples when annealing temperature is W13K, and at W23K it is homogeneous and stable laves phase structure. When the content of Dy and Tb is respectively 0.125 and 0.1, Tc of the alloys gradually increased from 222K to 298AK and 294K, close to room temperature. On the other hand, the magnetic entropy change reduced from-3.34JJ/Kg*K to -1.94J/kg*K and -2.08J/kg*K at magnetic field of 7T, at the same time the type of magnetic phase transition is typical second order phase transition characteristics. Through the results of magnetocaloric performance measurement, Tb-doped make lager effects of the curie temperature and the magnetic entropy change of (Ce1-xRx)Fe2 alloy samples.