YBa2Cu3-xFexOy的离子配位与结构转变

本文用穆斯堡尔效应、X射线衍射等手段,系统研究了掺铁的YBa₂Cu_3-xFe_xO_y(0.01≤x≤0.2)超导氧化物经过不同温度真空退火后超导转变温度T_c、相结构、氧含量与氧配位之间的关系,结果表明,铁主要占Cu(1)位,铁含量的增加和高温真空退火都引起正交相向四方相转变,T_c逐渐减小至零,但这两种转变过程的铁的配位结构和氧含量却不相同,对前者,相变是与出现相当数量的六配位F关键词：

ION COORDINATION AND STRUCTURAL TRANSITION OF YBa2Cu3-xFexOy

Critical temperature, phase structure, oxygen content and coordination of oxygen atoms were studied for Fe doped superconducting oxides YBa₂Cu_3-xFe_xO_y(0.01≤x≤ 0.2) after an-nealing at different temperatures by use of M?ssbauer spectroscopy and X-ray diffraction. The result shows that Fe ion occupies mainly Cu(l) position. Both the increase of Fe content and vacuum annealing at high temperature lead to the structural transition from orthorhombic, to tetragonal phase, and the critical temperature T_c goes to zero. However, in the former case, during the increase of Fe content the transition occurs when appreciable amount of Fe³⁺ ion with sixfold coordinate oxygen atoms exists, and is thus accompanied by the increase of oxygen content. But for vacuum annealing at high temperature, with the increase of annealing temperature the number of Fe ion with double oxygen coordination increases and oxygen content decreases, and the transition occurs when this double oxygen coordination dominates. Both these processes destroy the planar Cu-O configuration and lead to the decrease of T_c .Besides, the valence states of Fe atoms at different lattice sites are also determined and discussed.
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