Development of rare earth nitrides as magnetic refrigerant and regenerator material for cryogenic use.

采用HIP法制备了Gd、Tb、Dy、Ho、Er等氮化物及其二元氮化物。测量了它们的磁化强度和比热，评价了它们的磁熵变化和绝热退磁冷却。对其中一些样品的电导率也进行了测量。确定了该类材料适合作为氢液化磁冷却系统的制冷剂。合成了直径为0.85 ~ 1.0mm的GdN球形材料，干燥空气24h使其增重小于1%。将该球形材料充入磁致冷试验装置，在55-65K区域测得5度磁致冷。

Nitrides of Gd, Tb, Dy, Ho, Er and their binary nitrides were synthesized by the HIP method. Their magnetization and specific heat were measured to evaluate the magnetic entropy change and adiabatic demagnetization cooling. Electronic conductivities of some of their samples were measured as well. It was ascertained that this class of material is suitable for refrigerant of magnetic cooling system for hydrogen liquefaction. Spherical material of GdN with diameter of 0.85-1.0mm was synthesized and its weight gain caused by exposure to dry air for 24h was found less than 1%. This spherical material was charged into a magnetic refrigeration test device and a magnetic cooling of 5 degrees was measured in a region of 55-65K.