Pressure-dependent oxygen diffusion in superconducting Tl2Ba2CuO6+δ, YBa2Cu3O7−δ, and HgBa2CuO4+δ: Measurement and model calculation

Abstract

In a variety of high-temperature superconductors the transition temperature Tc has been found to depend on the sample’s detailed temperature and pressure history. Tl2Ba2CuO6+δ (Tl-2201) exhibits two distinct relaxation channels, one activated below 100 K and the other above 150 K, that have been attributed to oxygen ordering effects. In the present studies to 0.8 GPa we find that the activation energy for the low-temperature process, EALT(1 bar)≈0.25 eV, is independent of pressure, whereas the activation energy for the high-temperature process, EAHT(1 bar)≈0.75 eV, appears to increase with pressure yielding an activation volume ∼1.5 cm3/mol. The activation volumes for the diffusion of oxygen defects in the high-temperature superconductors Tl-2201, YBa2Cu3O7−δ (Y-123), and HgBa2CuO4+δ (Hg-1201) are estimated using a simple hard-sphere model and found to be roughly half the experimental values. For Tl-2201 this comparison supports an indirect “interstitialcy” diffusion path for oxygen defects, whereas for Y-123 and Hg-1201 direct “interstitial” diffusion paths are indicated.

Source-reported materials — not catalogue approval

Similar papers