REMARKABLE INFLUENCE OF HEAT-TREATMENT ON THE STRUCTURAL AND SUPERCONDUCTING PROPERTIES OF Y1-XPRXSRBACU3O6+Z

Preparation, structural and superconducting properties of Y1-zPrxSrBaC u3O6+z (YPSBCO) are reported. Preheating of the samples in argon prior to oxygen annealing not only increased the orthorhombic splitting but T-c also was enhanced by 5 to 14 K depending on x. Furthermore, this treatment induced superconductivity in the x = 0.70 sample and T-c was found to be 14 K. The slope dT(c)/dx decreased considerably compared to Y1-zPrxBa2Cu3O6+z, where superconductivity was destroyed for x grea ter than or equal to 0.55. The data seem to indicate that a knowledge of the structural and defect chemistry is essential to understand the behaviour of Pr in YPSBCO.