Degradation of MgB2 under ambient environment
Degradation of MgB2 under ambient environment
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MgB2在环境环境下的降解
DOI：
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
S. Indrakanti
中科院分区：
文献类型：
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作者：
A. Serquis;Y. Zhu;D. Peterson;F. M. Mueller;R. Schulze;V. Nesterenko;S. Indrakanti
几种工艺制备的样品的超导电性在环境条件下都有下降。用X射线光电子能谱(XPS)测量了致密的热等静压球团(HIPed)在大气暴露下的表面化学成分变化，研究了其降解机理。结果表明，颗粒间连通性差、颗粒尺寸较小的样品在暴露于环境条件下会随着时间的推移而降解。在这些样品中，超导转变温度不随时间变化，但超导转变变宽，迈斯纳分数降低。相比之下，我们的良好烧结和热等静压样品在环境条件下保持了几个月的稳定。XPS分析表明，降解与表面分解有关。我们观察到氧化镁的形成，主要是以氢氧化镁的形式，增加了C和O的含量，减少了表面层中的B浓度。
The superconductivities of samples prepared by several procedures were found to degrade under ambient environment. The degradation mechanism was studied by measuring the change of surface chemical composition of dense MgB2 pellets (prepared by hot-isostatic pressure, HIPed) under atmospheric exposure using x-ray photoelectron spectroscopy (XPS). Results showed that samples with poor connectivity between grains and with smaller grain sizes degrade with time when exposed to ambient conditions. In these samples, the TC did not change with time, but the superconducting transition became broader and the Meissner fraction decreased. In contrast, our well-sintered and the HIPed samples remained stable for several months under ambient condition. The degradation was found to be related to surface decomposition as observed by XPS. We observed the formation of oxidized Mg, primarily in the form of a Mg hydroxide, the increase of C and O contents, and the reduction of B concentration in the surface layer of MgB2 samples.