Complex Susceptibility of Bi2Sr2Ca1-xYxCu2Oy from Citrate Sol-Gel Precursors

In order to examine the dependence of the superconducting property of the double Cu-O layer system on the hole concentration, we measured the superconducting transition of Bi2Sr2Ca1-x Y x Cu2O y (0≦x≦0.4) compounds in terms of complex susceptibility, χ=χ′-iχ′′. The samples were synthesized by a citrate sol-gel precursor technique. The main advantages of this method are the shorter reaction time, the elimination of some steps such as centrifugation, and a fine control of pH. X-ray diffraction analysis showed that each sample has a single phase, although χ for x=0.1 indicates the existence of different superconducting phases. It has been revealed that the superconducting transition temperature T c apparently depends on the hole concentration, and the highest T c (95.2 K) was achieved for around x=0.1. The profiles of χ for five samples with different values of x are discussed.