THERMOELECTRIC-POWER AND THERMAL-CONDUCTIVITY IN YBA2(CU1-XFEX)(3)O-7-DELTA WITH OR WITHOUT EXCESS OF COPPER-OXIDE

Thermoelectric power and thermal conductivity of YBa2(Cu1-xFex)(3)O-7-delta polycrystals for 0<x<0.03 and with y% CuO (y equals 0 and 5) extrinsic impurity were simultaneously measured as a function of temperature. Samples were prepared following the same synthesis runs, and characterized by X-ray, EDX, and magnetic susceptibility techniques. When increasing copper oxide concentration, the transition is unaffected with respect to the pure sample, and the thermal transport coefficients correspond to very well oxygenated systems. Fe doped samples showed a lower transition temperature and features corresponding to low oxygenation systems. Fe doped sample with CuO revealed also the partial absorption of Fe by the ''extra CuO phase'' due to the 'dilution' of iron in the excess of CuO al grain boundaries. Fe-doping and excess CuO markedly reduce the thermal conductivity.