The superconducting properties and the effects of Yb substitution on (Y1-xYbx)Ba2Cu3O7-δ (Y123) withx = 0 to 1.0 were investigated. The powder X-ray diffraction method, scanning electron microscopy andelectrical resistance measurements were used to characterize the samples. All samples showed pureY123 phase except for x = 1 which showed some impurity peaks. The lattice parameters and unit cellvolume decreased as Yb content was increased indicating the smaller Yb3+ instead of the larger Yb2+was substituted at the Y3+ site. The resistance-temperature curves showed metallic normal statebehaviour in all samples. The superconducting transition temperature showed a slight decrease as Ybcontent was increased due to charge redistribution between the CuO chain and the CuO2 plane as smallerYb3+ replaced Y3+. Our results showed that for Y123 type structure, the ionic radius of the rare-earth ismore important than the valence state in forming a stable phase which can be superconducting or nonsuperconducting depending on the valence state of the rare earth ions. These results are useful inunderstanding the phase formation and transport mechanism of this material..
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