CRYSTAL-STRUCTURE AND RESISTIVITY STUDIES ON PRBA2-XPRXCU3O7-Y OXIDE SYSTEM

The compound PrBa2Cu3O7-y is not superconducting while most other RBa2Cu3O7-y (R = rare earth) compounds exhibit superconductivity in the 90 K range. The system PrBa2-xPr(x)Cu3O7-y has been prepared to study the effect of excess Pr at the Ba site on the structure, resistivity and magnetic behaviour of this system. It is observed that single-phase compounds in the above series form for x = 0.8-that is up to the composition Pr1.8Ba1.2Cu3O7-y. While stoichiometric PrBa2Cu3O7-y is orthorhombic, the compounds with excess Pr show tetragonal structure. Four-probe dc resistivity measurements show that all the single-phase compounds in the above series do not exhibit superconductivity and are semiconducting down to 12 K. Magnetic susceptibility measurements reveal deviation from Curie-Weiss behaviour starting at a characteristic temperature, which is taken to be the ordering temperature (T(N)) of the Pr moments. Both T(N) and overall resistivity decrease with increasing x and may have a common origin.