Structural and superconducting properties of Bi_1.7Pb_0.4Sr_2 − xYb_xCa_1.1Cu_2.1O_y system

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• 作者：A. Biju ; R.P. Aloysius ; U. Syamaprasad
• 关键词：(Bi ; Pb)-2212 superconductor ; Yb substitution ; Critical current density (J_C) ; Critical temperature (T_C)
• 刊名：Materials Letters
• 出版年：2007
• 期刊代码：59_0167577x
• 类别：ms
• 出版时间：February 2007
• 卷：61
• 期：3
• 页码：648-654
• 文件大小：970 K

摘要

The structural, electrical and superconducting properties of Bi_1.7Pb_0.4Sr_{2 − x}Yb_xCa_1.1Cu_2.1O_y system has been studied for different Yb concentrations. The samples are prepared by solid state synthesis in the polycrystalline bulk form. Structural analysis by X-ray diffraction, microstructural examination by SEM and measurements of electrical and superconducting properties have been conducted to study the effects of Yb substitution at Sr site. The critical temperature (T_C) and critical current density (J_C) are found to increase drastically with Yb substitution. Maximum values of T_C and J_C are observed for x = 0.3 and x = 0.2 respectively. The increase in T_C and J_C is explained due to the substitution effect of Ybp>3+p> in place of Srp>2+p> and consequent change in the hole concentration in the CuO₂ planes. Above the optimum levels T_C and J_C begin to reduce due to secondary phase formation. A metal–insulator transition originating from the change of carrier concentration is found to occur at higher doping level (x > 0.5).