The effects of cobalt substitution on the thermal diffusivity of YBa2Cu3O7−δ superconductor

Abstract

The thermal diffusivity r(T) of the cobalt-substituted sintered YBCO system, YBa2Cu3-xCoxOT-~ (x = 0.0, 0.1), has been measured to investigate effects of atomic substitution and charge carrier concentration on the thermal diffusion processes. The thermal diffusivity was measured in the temperature range 35-300 K using the transient-plane-source technique. The results show that, below To, the ~c(T) values of the doped (x=0.1) samples are lower than the corresponding values for the undoped (x = 0.0) samples. This may be due to the difference in the free-charge carrier concentrations of the two samples. A decoupling between the conducting Cu-O planes as a result of Co-doping in the chain sites may contribute to additional decrease in the thermal diffusivity of the doped sample. An attempt was made to explain the rise in the thermal diffusivity below Tc by adopting a recent theoretical model based on the existence of weakly damped collective electron excitations of Bose type, with acoustic dispersion relation (acoustic plasmons) inside the superconducting gap.

The Effective Thermal Transport in Composite Materials

“…This technique has an additional advantage of using a flat thin sensor, which makes it more suitable to substantially, reduce the contact resistance between the specimen and the sensor. This technique has been used several times to report thermal conductivity measurements over a wide range of temperatures (Gustafsson, 1991) & (Suleiman et al, 1996 including the www.intechopen.com…”