Synthesizing and physical properties of GdPr-123 high-Tc superconductor

Ceramic Gd1-xPrxBa2Cu3O7-y (GdPr-123) high-T-c superconductors have been synthesized by the standard solid state reaction method and characterized by XRD, SEM, TGA, and DT techniques in the range of x, 0.0 less than or equal to x less than or equal to 1.0 Samples have orthorhombic structure with Pmmm symmetry and there is a small percentage (less than I%) of the Ba sites occupied by Pr ions in some Pr-rich samples. In these samples a small trace of BaCuO2 and Pr BaO3 secondary phases persist with the main peaks at 2 theta approximate to 29.3 degrees and 28.9 degrees respectively. Microstructure analysis indicates a uniform grain size distribution with a mean size of 5 mu m. No significant change of grain size is shown throughout the range of x studied. The valence of Pr and Cu were determined by magnetization measurements in the temperature range 100 to 250 degrees K. These data reveal a valence of 3.86+ for Pr in all samples independant of x. The similarity of the superconducting and insulating properties in this system to those of the oxygen deficient RBa2Cu3O7-y (R-123) (R:Y or rare earth) system implies that the mechanism of superconductivity in high-T-c superconductors cannot be two-dimensional, even though the superconductive current occurs in two dimensions.