SUPERCONDUCTING TRANSITION TEMPERATURES AND NORMAL-STATE ELECTRICAL RESISTIVITIES OF Tm_1-xPr_xBa₂Cu₃O_7-\delta

Superconducting transition temperature T_c and normal-state electrical resistivities \rho of the Tm_1-xPr_xBa₂Cu₃O_7-\delta system have been measured. The results indicate that T_c remains constant for x = 0 to 0.08 before it drops steadily with higher x. Following the Abrikosov-Gor'kov model, a total suppression of superconductivity occurs at a critical Pr concentration x_cr≈0.56. It is found for the first time, as far as we know, that the logarithmic resistivity at 270 K increases linearly with increasing x, yielding \rho = \rho₀e^ax. Judging from the relation between d\rho/dT and x, a metal to insulator transition occurs just beyond x_cr.