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Synthesis of New Pb-based 1222 Layered Cuprates in the (Pb,S)Sr2(RE,Ce)2Cu2O z (RE=Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, and Y) System
Authors:Hiroyuki Sasakura  Yoshiya Akagi  Masashi Tanaka  Shigeki Tsukui  Motoaki Adachi
Affiliation:1. Department of Physics, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu-shi, Shizuoka, 431-3192, Japan
2. Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University, Higashi-Hiroshima-shi, Hiroshima, 739-8527, Japan
3. Department of Chemical Engineering, Graduate School of Engineering, Osaka Prefecture University, Naka-ku, Sakai-shi, Osaka, 599-8531, Japan
Abstract:A new family of the Pb-based layered cuprate with the 1222 structure has been synthesized in the (Pb,S)Sr2(RE,Ce)2Cu2O z (RE=Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, and Y) system. The almost-single phase samples are obtained for x=0.25 and y=1.0 in the composition of (Pb1?x S x )Sr2(RE2?y Ce y )Cu2O z . Each of the samples has the crystal structure with a tetragonal symmetry. Both of the lattice parameters a and c are decreasing with the decrease of the ionic radius of RE element. Among these samples, the sample with RE=Er has the smallest resistivity in the whole temperature range and the slope of the resistivity versus temperature is the most gentle. Despite annealing under O2 atmosphere at high-pressure of 121 atm, this sample is a semiconductor with the transport process characteristics of three-dimensional variable range hopping conduction. Then the samples of RE=Er with smaller y are investigated for the composition of (Pb0.75S0.25)Sr2(RE2?y Ce y )Cu2O z , the sample with y=0.4 is found to show an onset of resistivity drop phenomenon at about 11 K with the decrease of temperature. Moreover, we also discover that the samples of RE=Ho with y=0.4 show an onset of the resistivity dropping at over 20 K and zero resistivity at 13 K. From these results, the present (Pb0.75S0.25)Sr2(RE2?y Ce y )Cu2O z system is considered to be a new family of the Pb-based superconducting cuprates with the 1222 structure.
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