Anisotropy of the thermal conductivity of bulk melt-cast Bi-2212 superconducting tubes

Abstract

We investigate experimentally the anisotropy of the temperature dependence of the thermal conductivity of bulk Bi2Sr2CaCu2O8 (Bi-2212) cylinders fabricated by the melt-cast process. The thermal conductivity κ(T) along the axial and azimuthal directions are found to be equal within experimental uncertainty, while κ along the radial direction is found to be ~ 40% larger than the other two. The results are in qualitative agreement with the weak partial texture of such tubes, corresponding also to an anisotropy of the resistivity ρ(T) above the critical temperature Tc. This resistivity anisotropy in the normal state is responsible for an anisotropy of the electronic contribution of thermal conductivity (∆κe), which is much smaller than the anisotropy ∆κ of the total thermal conductivity. This indicates an anisotropic contribution of the phonons. The temperature dependence of the specific heat C(T) is also measured and shows that C(T)/T exhibits a well-defined maximum close to Tc. The combination of these experimental data can be used for assessing the thermal effects in bulk melt-cast Bi-2212, and underline the importance of taking the anisotropy of κ into account, e.g. for predicting the self-heating when the material is subjected to losses.

Evaluation of irradiation effects on the microstructure and properties of Ag-sheathed Bi-2212 superconducting round wire for future application in CFETR

“…It is widely accepted that the current in the Bi-2212 round wire generally transports through the grain boundary and the a-b plane within the grain, while the current flow can be readily inhibited by the lattice distortion due to the presence of defects [15][16][17][18][19][20][21]. As demonstrated by the heavily disordered atomic arrangement in the irradiated sample (figures 6(b) and (d)), it can be briefly concluded that the irradiation defects could disrupt the connectivity of the Bi-2212 superconducting region, thereby resulting in the J C degradation of Bi-2212 round wire, consistent well with the previous reports [12,18,19].…”

“…It is well-known that the Bi-2212 superconductor possesses a number of inherent merits, such as excellent critical current density (J C ) at high magnetic fields (>25 T), good phase stability, and high phase-transition temperature (T C ). More importantly, the Bi-2212 has been currently considered as the only HTS that can be made into round wires with isotropic cross sections, greatly simplifying the winding process for coils and cables [7][8][9][10][11][12]. Therefore, the Bi-2212 exhibits great potentials and promising for the applications in fusion reactors in years to come.…”