The thermal conductivity of $\mathrm{Y}{\mathrm{Ba}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-\delta }$ and $\mathrm{Y}{\mathrm{Ba}}_2{\mathrm{Cu}}_{3-x}{\mathrm{Co}}_x{\mathrm{O}}_{7-\delta }\mathrm{}(x=0.1\mathrm{})\mathrm{}$ 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 $2\Delta \mathrm{}\left(T\right)\mathrm{}$.

• Received 19 July 1995

DOI:https://doi.org/10.1103/PhysRevB.53.5901