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首页> 外文期刊>IEEE Transactions on Magnetics >Oxidation kinetics in oxygen deficient YBa/sub 2/Cu/sub 3/O/sub 7-x/ studied by neutron powder diffraction
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Oxidation kinetics in oxygen deficient YBa/sub 2/Cu/sub 3/O/sub 7-x/ studied by neutron powder diffraction

机译：中子粉末衍射研究缺氧YBa / sub 2 / Cu / sub 3 / O / sub 7-x /中的氧化动力学

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摘要

A high-resolution, multidetector neutron powder diffractometer has been constructed and used for online studies of the oxidation kinetics in ceramic powders of oxygen-deficient YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBACUO). The structural phase transition between ordered orthorhombic and disordered tetragonal phase has been studied in pure oxygen and under vacuum. A continuous transition at 655 degrees C is observed in a pure oxygen atmosphere under equilibrium conditions, whereas an irreversible transition is observed at 470 degrees C under vacuum. Reduced YBACUO corresponding to x approximately=1.0 has been obtained by evacuation at 705 degrees C and has been shown to be stable in air. The oxidation processes of reduced YBACUO in a pure oxygen atmosphere have been studied using a semidynamical stepwise increase in temperature and under isothermal conditions. The results show that the in-diffusion under oxidation of reduced YBACUO is more easily accomplished than the corresponding out-diffusion process under reduction. From the structural data it is concluded that oxidation takes place in a mixed-phase medium of coexisting tetragonal and orthorhombic phases.
机译：构造了高分辨率的多探测器中子粉末衍射仪，用于在线研究缺氧的YBa / sub 2 / Cu / sub 3 / O / sub 7-x /（YBACUO）陶瓷粉末中的氧化动力学。在纯氧和真空条件下，研究了有序正交相和无序四方相之间的结构相变。在纯氧气氛中，在平衡条件下，观察到在655℃发生连续转变，而在真空下在470℃观察到不可逆转变。通过在705摄氏度下抽真空获得了相当于x大约= 1.0的还原YBACUO，并且已证明在空气中稳定。使用半动力学逐步升高温度并在等温条件下研究了纯氧气氛中还原的YBACUO的氧化过程。结果表明，还原后的YBACUO在氧化作用下的内扩散比还原下相应的外扩散过程更容易实现。从结构数据可以得出结论，氧化发生在四方和正交相共存的混合相介质中。

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