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) ext rinsic impurity were simultaneously measured as a function of temperat ure. Samples were prepared following the same synthesis runs, and char acterized by X-ray, EDX, and magnetic susceptibility techniques. When increasing copper oxide concentration, the transition is unaffected wi th 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 oxygena tion systems. Fe doped sample with CuO revealed also the partial absor ption of Fe by the ''extra CuO phase'' due to the 'dilution' of iron i n the excess of CuO al grain boundaries. Fe-doping and excess CuO mark edly reduce the thermal conductivity.