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利用Hall系数测量、热重分析和M(?)ssbauer谱等多种实验手段并结合有效价键模型计算,研究了(Tl_(0.5)Pb_(0.5))(Sr_(0.8)Ba_(0.2))_2Ca_2(Cu_(1-x)Fe_3)_3O_(9+v)超导体中由于铁掺杂所诱导的额外氧缺陷对载流子浓度和微结构的影响.在低浓度掺杂水平(x=0～0.05)上,铁掺杂样品的超导转变温度与载流子浓度有非常明显的对应关系,零电阻温度T_∞随铁掺杂量线性降低.Hall系数测量结果也表明Hall载流子浓度随铁含量x的增加也呈线性下降趋势.热重分析(TG)结果表明化合价较高的Fe~(3+)离子替代Cu~(2+)离子后,将有可能诱导额外氧进入晶格而形成额外氧缺陷.在电荷转移模型基础上并借助于有效价键的理论计算,可以得到载流子浓度的降低来源于额外氧缺陷对载流子的强局域化的束缚作用.同时额外氧所引起的Cu-O面的畸变也使得超导转变温度降低.还分析讨论了额外氧缺陷的局域结构,包括氧的占位和Fe,O的位移关系.
(Tl_ (0.5) Pb_ (0.5)) (Sr_ (0.8) Ba_ (0.2)) was investigated by means of Hall coefficient measurement, thermogravimetry and M (?) Ssbauer spectroscopy combined with effective valence bond model The effects of additional oxygen defects induced by iron doping on carrier concentration and microstructure were investigated at low doping level (x = 0 ~ 0.05), the superconducting transition temperature and the carrier concentration of the iron-doped samples have a very clear corresponding relationship, the zero-resistance temperature T_∞ decreases linearly with the iron doping content.The measurement results of Hall coefficient also show that the Hall carrier concentration The results also showed that the increase of iron content x showed a linear decrease trend.The result of TG showed that the replacement of Cu 2+ ions by Fe 3+ ions with higher valence could induce extra oxygen to enter the lattice Forming additional oxygen defects.On the basis of charge transfer model and by the theoretical calculation of effective valence bond, the reduction of carrier concentration can be attributed to the strong localization effect of extra oxygen defects on carriers.At the same time, the additional oxygen The resulting distortion of the Cu-O surface also lowers the superconducting transition temperature.The local structure of additional oxygen defects is also analyzed and discussed, including Placeholder and Fe, O, displacement relationship.