THERMAL-CONDUCTIVITY OF IMPURITY-DOPED HIGH-T(C) SUPERCONDUCTORS

The thermal conductivity K(T) of polycrystalline YBa2(Cu1-xMx)3O7 with M=Zn and Al (0 less-than-or-equal-to x less-than-or-equal-to 0.1) and Y1-yRyBa2Cu3O7 with R=Pr and Gd(0 less-than-or-equal-to y less-than-or-equal-to 1.0) has been measured for temperatures 1.2 less-than-or-equal-to T less-than-or-equal-to 200 K. In the pure material, K(T) decreases slightly with decreasing temperature above T(c) and below T(c) there is a strong enhancement of K(T) reaching a maximum at approximately 50 K followed by a sharp decrease. At temperatures below 10 K a T2 dependence is evident similar to behavior reported for amorphous systems with glasslike phonon scattering on the tunneling states. Doping with Zn or Pr rapidly depresses T(c) and also depresses the maximum in K(T) even at concentrations that remain superconducting. This effect is observable to a lesser degree for the Al and Gd dopants. Comparisons between the K(T) behavior for impurities that do not depress T(c) with those that diversely alter the superconducting properties are presented together with an analysis of the data using the Tewordt-Wolkhausen (TW) theory.