EFFECT OF COBALT DOPING ON THERMAL-CONDUCTIVITY OF YBA2CU3O7-DELTA SUPERCONDUCTOR

The thermal conductivity of YBa2Cu3O7-delta and YBa2Cu3-xCoxO7-delta ( x = 0.1) sintered compounds has been measured to investigate the effec t of Co doping on the thermal conduction processes. The measurements w ere performed using the transient-plane-source technique. The thermal conductivity of the doped sample qualitatively resembles that of the c orresponding undoped sample, but with values a factor of 2 lower. This decrease in thermal conductivity is attributed to scattering mechanis ms due to enhancement of the microstructural imperfections and the dec oupling between the conducting Gu-O planes as a result of Go-doping in the chain sites. An attempt was made to interpret the peak of the the rmal conductivity below T-c in terms of a theoretical model based on w eakly damped collective electron excitations of the Bose type, with an acoustic dispersion relation (acoustic plasmons), inside the supercon ducting gap 2 Delta(T).