Pressure effects on the carbon nano-tube embedded Y-123 superconductors

It has been known that applying pressure and doping carbon nano-tubes (CNTs) can each affect the behavior of high temperature superconductors. Here, bridging these two effects in order to see how they can interplay, we investigate how the dc resistivity varies in both pure and CNT-doped polycrystalline YBa2Cu3O7−δ (Y-123) compounds under hydrostatic pressure. We demonstrate that the broadening of the resistivity transition in the CNT-doped samples (of 0.7 wt%) is smaller than the undoped samples. In addition, by increasing applied pressure, the doped samples exhibit a higher rate of the increase of the transition temperatures Tcon and Tcmid than the undoped samples. Interestingly as well, under applied pressure of 1.5 GPa, it is found that Tcon for the doped samples (99.39 K) is relatively higher than in the undoped samples (96.88 K). The doped samples also show more robustness versus applied pressure in the sense that they have smaller variations of resistivity. In particular, we observed that the increase rate of the normal resistivity in the CNT-doped samples is nearly four times smaller than the undoped samples. This may be a manifestation of relative robustness of the doped samples against fractures of the links between grains. These observations, overall, may suggest that the CNT doping, due to unique mechanical characteristics of CNTs, can enhance superconductivity properties of Y-123 superconductors under applied pressure.