THERMAL-CONDUCTIVITY OF DOPED YBCO SINGLE-CRYSTALS

Thermal conductivity K of the three systems: oxygen deficient YBa2Cu3O x(x=6.05-6.95), Y1-2Pr2Ba2Cu3Ox (z=0-1, x=6.05-6.95), nnd YBa2(Cu1-yZn y)(3)O-6.95(y=0.0-0.05) in a-b plane have been systematically studied as function of temperature and magnetic field. The evolution of the th ermal conductivity upon doping depends on the origin of metal-insulato r transition. The unusual temperature dependence K(T) of non-metallic crystals suggests that some unconventional mechanism of phonon relaxat ion dominates in these crystals. Analysis of the experimental data con firms the phononic explanation of the K(T) for YBa2Cu3O7.