We have achieved the preparation of theY(Ba1−xSrx)2Cu3O7 compounds with x ranging from 0 to 1 by substituting a small amount of Cu with Mo. It was observed that the superconducting transition temperature, Tc, first decreases linearly with Sr-content until x0.4, where a sharp drop in Tc occurs. The Tc for the sample with x=0.1 is about 40 K. X-ray structure analysis shows that a sharp drop in Tc at a critical concentration corresponds to the crystal change from orthorhombic to tetragonal.
