几种室温磁致冷材料磁热效应的比较

Evaluation on Magnetocaloric Effect of Magnetic Refrigerating M aterials Near Room Temperature

磁热效应是磁性材料具有的重要特征,表征材料磁热效应的大小用等温磁熵变ΔS、绝热温变ΔTad两个参数。用热力学原理推导了ΔS与ΔTad的关系,表明不同材料在不同的温度区间进行磁热效应比较时,由于材料的本性不同,ΔTad不会随ΔS的增大而增大,而是以T/C的比例系数随之变化,评判材料的磁热效应必须兼顾ΔS与ΔTad两个参数;从工程应用的角度强调了ΔTad参数的重要性;对近几年出现的新的近室温磁制冷材料的磁热效应及在工程上的应用进行了评价。

Magnetocaloric effect(MCE) is the intrinsic properties of magn et ic materials. Isothermal magnetic entropy change ΔS and adiabatic temperatu re change ΔTad are two factors which are used as the merit of MC E of magnetic refrigerating material. The relationship between ΔS and ΔT ad was deduced according to the principles of thermodynamics. The i sothermal entropy change is proportional to the adiabatic temperature change wit h a factor of T/C(T is temperature, C is heat capacity). When the co mparison of the magnetocaloric effect is made in two different materials, the isothermal en tropy change as well as adiabatic temperature change must be considered. The MCE and the engineering appliance for the new kinds of magnetic refrigerating materials near room temperature which are discovered in recent years are discussed.