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一、引言 Ba-Y-Cu-O材料具有液氮温区超导特性的发现,使人们对此发生了极大兴趣。这种超导材料的性能与烧结温度和烧结气氛有关。事实上,不同的烧结和退火条件将严重影响样品的氧含量。X射线衍射照相及中子衍射研究表明,具有畸变钙钛矿结构的超导材料Ba_2Y_1Cu_3O_(7-δ)中氧空位起重要作用。由于超导特性根本上是由材料的电子结构特性决定的,因此不同退火条件下,这些材料的电子能态的变化及其影响是需要认真研究的。
I. INTRODUCTION The discovery of Ba-Y-Cu-O materials with superconducting properties at liquid nitrogen temperature has led to great interest. The performance of this superconducting material is related to the sintering temperature and sintering atmosphere. In fact, different sintering and annealing conditions will seriously affect the oxygen content of the sample. X-ray diffraction and neutron diffraction studies show that oxygen vacancies play an important role in Ba_2Y_1Cu_3O_ (7-δ) superconducting materials with distorted perovskite structure. Since superconductivity is fundamentally determined by the electronic structure of the material, changes in the electron energy states of these materials and their effects under different annealing conditions require careful study.