ELECTRICAL-RESISTIVITY OF THE SUPERCONDUCTOR-INSULATOR GD1-XPRXBACU3O7-Y (0-GREATER-THAN-OR-EQUAL-TO-X-GREATER-THAN-OR-EQUAL-TO-1) SYSTEM

Gd1-xPrxBa2Cu3O7-y polycrystalline specimens in the orthorhombic form for 0 less than or equal to x less than or equal to 1 have been prepared by a solid state reaction and their electrical resistivity has been measured at temperatures ranging from 300 to 10 K. The measured resistivity increased with increasing x, exhibiting a metallic behaviour for T > T-c and x < 0.5. For x > 0.5, the superconductivity of these specimens was suppressed and a metal-insulator transition occurred. The resistivity obeyed a fit of rho = A/T + BT according to the Anderson-Zou theory. In the insulating region, the variable range hopping cannot be explained as the sole mechanism responsible for the conduction. The value of the superconducting transition temperature determined by the data on resistivity is quenched with an increase in x following the Abrikosov-Gor'kov pair-breaking theory. However, for small values of x the variation of T-c is nonlinear.