Samples of HgBa2CuO4+δ (Hg-1201) were annealed under various conditions. After carefully controlling annealing time, annealing temperature (Ta), and O2 partial pressure (P0), we were able to find the reversible annealing conditions for Hg-1201. Under 1 atm O2 at 260°C≤Ta≤400°C, the obtained Tc is nearly the same (∼97 K). However, it decreases quickly with Ta≳300°C in high vacuum (P0∼10-8 atm), and reaches zero at Ta=400°C. On the other hand, T c decreases with the decrease of Ta in high-pressure O2 (∼500 atm) and reaches ∼20 K at about 240°C. In the entire annealing region, the oxygen surplus varies significantly from 0.03 to 0.4, and a wide range of Tc variation (0→97 K→20 K) was obtained with anion doping alone.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)