Synthesis of (CaxLa1.00−x)(Ba1.75−xLa0.25+x)Cu3Oz tetragonal superconductor by amorphous metal complex method

Polycrystalline samples of tetragonal superconducting (CaxLa1.00−x)(Ba1.75−xLa0.25+x)Cu3Oz isostructural to YBa2Cu3O7−δ were prepared by a simple aqueous solution technique using citric acid (CA). The results of both X-ray diffraction (XRD) and Raman scattering analyses indicated that the polycrystalline samples for the Ca content (x) from 0.1 to 1.0 were of single phase with respect to superconductivity and isostructural to tetragonal YBa2Cu3O7−δ phase. The dependence of Tc onset values for (x) from 0.1 to 1.0, determined precisely from the ac complex magnetic susceptibility measurements, had a “bell-shaped” character. The values increased from 39.6 K for x=0.1 to 78.7 K for x=0.4, remained almost constant at 80 K between x=0.5 and x=0.6, and then decreased to 44.6 K for x=1.0.