Effect of cobalt doping on thermal conductivity of YBa₂Cu₃O_7-δ superconductor

The thermal conductivity of YBa₂Cu₃O_7-δ and YBa₂Cu_3-xCo_xO_7-δ(x=0.1) sintered compounds has been measured to investigate the effect of Co doping on the thermal conduction processes. The measurements were performed using the transient-plane-source technique. The thermal conductivity of the doped sample qualitatively resembles that of the corresponding undoped sample, but with values a factor of 2 lower. This decrease in thermal conductivity is attributed to scattering mechanisms due to enhancement of the microstructural imperfections and the decoupling between the conducting Cu-O planes as a result of Co-doping in the chain sites. An attempt was made to interpret the peak of the thermal conductivity below T_c in terms of a theoretical model based on weakly damped collective electron excitations of the Bose type, with an acoustic dispersion relation (acoustic plasmons), inside the superconducting gap 2Δ(T).