Structural and superconducting properties of neodymium added (Bi,Pb)₂Sr₂CaCu₂O_y

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• 作者：A. Biju ; P.M. Sarun ; R.P. Aloysius ; U. Syamaprasad
• 关键词：A. Superconductors ; B. Electrical properties ; C. X-ray diffraction
• 刊名：Materials Research Bulletin
• 出版年：2007
• 期刊代码：60_00255408
• 类别：ms
• 出版时间：4 December 2007
• 卷：42
• 期：12
• 页码：2057-2066
• 文件大小：1272 K

摘要

The effects of neodymium (Nd) addition on the phase evolution, structural and superconducting properties of (Bi,Pb)₂Sr₂CaCu₂O_y [(Bi,Pb)-2212] prepared by solid state synthesis in bulk polycrystalline form were studied. The Nd content was varied from x = 0 to 0.5 on a general stoichiometry of Bi_1.7Pb_0.4Sr_2.0Ca_1.1Cu_2.1Nd_xO_y. The samples were characterized by differential thermal analysis (DTA), powder X-ray diffraction, scanning electron microscopy (SEM) equipped with energy dispersive X-ray analysis (EDX), resistance–temperature (R–T) measurements and superconductivity measurements at 64 K. It was found that the melting temperature of (Bi,Pb)-2212 slightly increases and the endotherm broadens due to the Nd-addition. The c-lattice parameter initially decreases and then increases with Nd addition. The critical temperature (T_C) and the critical current density (J_C) of the added samples are highly enhanced. The added sample shows a maximum onset critical temperature (T_C-onset) of 95.56 K (x = 0.3) and a maximum critical current density of 719 A/cmp>2p> at 64 K (x = 0.2) against 76.7 K and 100 A/cmp>2p>, respectively, for the pure sample. The results show that the enhancement in superconducting properties are not due to any improvement in microstructure or grain growth, but due to a decrease in hole concentration as a result of Nd doping, which changes the system from ‘over-doped condition’ to ‘optimally doped condition’.