氧含量对Fe掺杂YBCO体系中载流子局域化与离子团簇效应的影响

对YBa₂Cu_3-xFe_xO_y（x=00，01，02 ）和YBa₂Cu_2.8Fe_0.2O_y（y=705—653 ）系列样品的氧含量、霍尔系数和超导电性进 行了系统的研究.结果表明，氧含量的变化对样品中载流子的输运和转移及超导电性有重要 影响；适当增加氧含量可以减缓Cu(1)位元素替代对超导转变温度T_c的抑制；在 CuO₂面上参与输运的载流子（空穴）浓度是影响样品超导电性的关键因素.从电 荷转移模型出发 ，结合掺杂离子引起的载流子局域化和离子团簇效应，对载流子浓度随掺杂量和氧含量的变 化从微观结构方面进行了讨论.元素替代量的增加或者氧含量的降低（相同替代量的情况下 ）都将导致Cu-O链区的有效氧空位增多，导致替代元素的离子团簇效应和载流子局域化效应 趋于增强，这是引起参与输运的载流子浓度下降，进而导致T_c降低的主要原因.关键词：氧含量霍尔系数载流子局域化离子团簇效应

Effect of oxygen content on carrier localization and ion-cluster effect for the Fe-doped YBCO system

The oxygen content, Hall coefficient and superconductivity are systematically studied on YBa₂Cu_3-xFe_xO_y(x=00, 01 , 02) and YBa₂Cu_2.8Fe_0.2O_y(y=705—653) systems. The results show that ox ygen content has a great influence on the transport and transfer of carriers and the superconductivity of the samples, the suppression of T_c caused b y Cu( 1) site substitution could be weakened by the increase of oxygen content to some extent. The carrier (holes) density in CuO₂ plane plays a key role i n affecti ng the superconductivity. Based on the charge transfer model, and considering th e carrier localization and ion-cluster effect resulting from Fe substitution on Cu(1) site, we have discussed the change of carrier density caused by the oxygen content and Fe doping concentration. It proves that with the increase of Fe dop ing concentration or the decrease of oxygen content (for the same doping concent ration), the efficient oxygen vacancy increases, which enhances the ion-cluster effect and the carrier localization effect, resulting in the decrease of carrier density that participats in superconducting transport in the CuO₂ pl ane, and accordingly, the decrease of T_c.