YBa_2Cu_3O_（6＋x）高温超导体的临界温度与氧含量关系的逾渗理论分析

Percolation-Theory Analyses of the Relation between Critical Temperature and Oxygen Content in High-Tc Superconductor Yba_2Cu_3O_(6+x)System

本文提出了一种局域氧有序的限制通渗模型，从理论上计算出了ＴＢａ２Ｃｕ３Ｏ６＋ｘ高温超导体临界温度Ｔｃ与氧含量之间的关系曲线，与实验曲线符合得非常好．并对Ｔｃ～ｘ实验曲线上出现的＂台阶＂现象进行了分析．随着ｘ的增加出现了两种结构相变：四方相到正交相、正交（Ⅰ）相到正交（Ⅱ）相的转变．这些转变有逾渗机制．

In the present paper, a limited short-range-order-oxygen percolation model is proposed, thecurve of critical temperature To as a function of oxygen content theoretically is calculated in highTc superconductor YBa2Cu3O6+x system,and shows good agreement with the experimental curve. Andthe "plateaus"on the experimental curve Tc-x are analysed. With the increase of x two structuretransitions occu r: tetragonal-orthorhombio phase transition and orthorhombic (Ⅰ)-orthorhombic (Ⅱ)phase transition. There are Percolative mechanisms in those transitions.