1. Optimization of the Pr doping in the (Bi 1.7 Pb 0.3 )(Sr 2-x Pr x )CuO 6+  superconducting series Y. C. Chu 1 ( 朱禹臻 ), H.-C. I. Kao 1 ( 高惠春 ), D. C. Ling 2 ( 林大欽 ), H. S. Sheu 3 ( 許火順 ) and T. S. Chan 3 ( 詹丁山 ) 1 Department of Chemistry, Tamkang University, Tamsui 251, Taiwan 2 Department of Physics, Tamkang University, Tamsui 251, Taiwan 3 National Synchrotron Radiation Research Center, Hsinchu 300, Taiwan *virus777787@hotmail.com Abstract A series of Bi-2201 having the nominal composition of (Bi 1.7 Pb 0.3 )(Sr 2-x Pr x )CuO 6+δ with 0.050  x  0.50 was prepared by the solid state reaction method. All of them have the orthorhombic phase with a space group of Amaa. Orthorhombicity, 2 (a  b)/(a + b), decreases with increasing the amount of Pr content. The highest T c (20.1 K) is found in the sample with x = 0.40, which has an optimal hole concentration of 0.278(2) analyzed by an iodometric titration method. Hole concentrations with respect to the amount of Pr substitution. Fig. 4. Oxygen stoichiometry (y) and hole concentration (p) dependence with x for (Bi 1.9 Pb 0.1 )(Sr 2-x Pr x )CuO y samples. Fig. 5. T c dependence with hole concentration (p) for (Bi 1.9 Pb 0.1 )(Sr 2- x Pr x )CuO y samples. Fig. 1. XRD patterns of (Bi 1.7 Pb 0.3 )(Sr 2- x Pr x )CuO y samples with (0.050  x  0.50). Fig. 2. Rietveld refinement result of a (Bi 1.7 Pb 0.3 )(Sr 2-x Pr x )CuO 6+  with x = 0.40. Fig. 3. Unit-cell axes dependence with x for the (Bi 1.7 Pb 0.3 )(Sr 2-x Pr x )CuO y samples.  All of them are single-phase compounds with orthorhombic crystal system.  Impurity phases SrCuO 2+  and related compounds, were not found.  The R wp obtained from the Rietveld refinement on this samples is between 8  10%.  The space group of Amaa is used for the Rietveld analysis for the single phase samples.  Oxygen stoichiometry increases and hole concentration decreases with increasing Pr content.  It is a hole filling effect and the optimal T c of 20 K with p = 0.278(2) in the x = 0.40.  The a- and c-axis decrease with increasing x, while the b-axis increases with increasing x.  Pr successfully replaces the position of Sr site. Experimental  Bulk samples of (Bi 1.7 Pb 0.3 )(Sr 2-x Pr x )CuO 6+  were prepared by a conventional solid-state reaction method.  Mixed powder was calcined at 805°C for 26 h in a box furnace with five intermittent grindings. It was reground and pressed into pellets, sintered at 805°C for 24 h and quenched to room temperature.  Unit cell parameters were determined by the Rietveld refinement method. GSAS for the structure analysis. T c measured by a standard 4- probe method. Oxygen stoichiometry and the hole concentration of the compound were determined by an iodometric titration method. Acknowledgment This work is financially supported by the National Science Council of Taiwan. Reference [1] J. B. Goodenough, J. Zhou, Phys. Rev. B 42 (1990) 4287. [2] C. Michel, M. Hervieu, M. M. Borel, A. Grandin, F. Deslandes, J. Provost, B. Raveau, Z. Phys. B 68 (1987) 421. [3] J. Akimitsu, A. Y. Amazaki, H. Sawa, H. Fujiki, Jpn. J. Appl. Phys. 26 (1987) L2080. [4] H. Maeda, Y. Tanaka, M. Fukutomi, and T. Asano, Jpn. J. Appl. Phys. 27 (1988) L209. [5] R. Yoshizaki, H. Ikeda, L. X. Chen, M. Akamatsu, Physica C 224 (1994) 121. [6] W. L. Yang, H. H. Wen, Y. M. Ni, J. W. Xiong, H. Chen, C. Dong, F. Wu, Y. L. Qin, Z. X. Zhao, Physica C 308 (1998) 294. [7] S. Ono, Y. Ando, Phys. Rev. B 67 (2003) 104512. [8] Z. Mao, C. Fan, L. Shi, Z.Yao, L. Yang, Y. Wang, Phys. Rev. B 47 (1993) 14467. [9] H.W. Zandbergen, W. A. Groen, F. C. Mijhoff, G. Tendeloo, S. Amelinckx, Physica C 158 (1988) 325. [10] P. L. Gay, P. Day, Physica C 152 (1988) 335. [11] A. K. Cheetham, A. M. Chippendale, S. J. Hibble, Nature 333 (1988) 21. [12] G. Xu, Z. Mao, X. Xu, M. Tian, L. Shi, Y. Zhang, J. Phys. Condens. Matter 9 (1997). 5137. [13] Z. Mao, M. Fain, M. Ji, J. Zhu, J. Zuo, R. Wang, Y. Wang, Y. Zhang, Phys. Rev. B 49 (1994) 9857. [14] I. Chong, T. Terashima, Y. Bando, M. Takano, Y. Matsuda, T. Nagaoka, K. Kumagai, Physica C 290 (1997) 57. [15] T. Amano, M. Tange, M. Yokoshima, T. Kizuka, S. Nishizaki, R. Yoshizaki, Physica C 412 (2004) 230. [16] K. Osamuraa, S. Satoa, W. Zhanga T. Kizua, Physica C 186 (1991) 589. [17] A. C. Larson, R. B. von Dreele, Report La-UR-86-748, Los Alamos National Lab. Los Alsmos, NM, USA (1990). [18] E. H. Appelman, L. R. Moress, A. M. Kini, U. Geiser, A. Umezawa, G. W. Crabtree, K. D. Carlson, Inorg. Chem. 26 (1987) 1834.