烧结温度对MgB_2超导体宏观特征和显微结构的影响

Effect of sintering temperature on the macro-characteristics and microstructure of MgB2 superconductor

Mg粉、B粉按1．03：2的比例混合、压制成型后，在流通高纯氩气的条件下分别于660、700、750、800、850和900℃烧结1h，制备出MgB2块材。利用X射线衍射仪、扫描电子显微镜和阿基米德方法等，分别研究了样品的物相组成、显微结构和密度等。结果表明，随着烧结温度的升高，样品的非超导相Mg和MgBx（x=4、6或12）的含量、体积膨胀系数、质量损失率、密度及MgB2的晶粒尺寸都发生变化。750～850℃烧结时，可得到由MgB2和少量MgO组成、晶粒较小、密度较高的MgB2超导体。

Mg powder and B powder with a ratio of 1.03 ： 2 were well mixed and pressed into pellets. Samples were sintered for lh at 660, 700, 750, 800, 850 and 900℃, respectively, in a flow of high purity argon gas. X- ray diffractometer, scanning electron microscopy and the Archimedes method et al. were used to investigate the phase composition, the microstructure, the density and so on of MgB2 samples. It is revealed that the macrocharacteristics and the microstructure of the MgB2 bulk, such as the content of the non-superconducting phase of Mg and MgBx（x=4, 6 or 12）, the volume expansion coefficient, the mass loss rate, the density and the size of MgB2 grain, changes with the sintering temperature increasing. The high content of MgB2, the small grain size and the high density, which is beneficial to the superconductivity, can be achieved in the MgB2 bulks synthesized between 750 and 850℃.