Synthesis of high-purity YbBa₂Cu₃O_7-d and LuBa₂Cu₃O_7-d superconductors by polymerizable complex method

Polycrystalline samples of YbBa₂Cu₃O_7-d and LuBa₂Cu₃O_7-d were prepared by polymerizable complex method. The combined results of both X-ray diffraction and Raman scattering analyses indicated that YbBa₂Cu₃O_7-d sample was of single phase when the samples were sintered in a low oxygen partial pressure (1%) at relatively low temperature (845°C). On the other hand, LuBa₂Cu₃O_7-d sample was only slightly contaminated with a very small amount of Lu₂BaCuO₅ and BaCuO₂ impurities when the sample was prepared under the same condition as YbBa₂Cu₃O_7-d. Ac complex magnetic susceptibility measurements exhibited that a transition into the superconducting state for YbBa₂Cu₃O_7-d and LuBa ₂Cu₃O_7-d samples was sharp and smooth, implying that both of the samples were of "superconducting" single phase. The T_c onset values of the YbBa₂Cu₃O_7-d and LuBa₂Cu₃O_7-d, were 93.4 and 92.3 K, respectively.