Abstract
Low-temperature oxygen annealing was performed on Na-doped and undoped Hg-1223 phases. It is argued that Na could perturb the electronic band structure of the material by changing the distribution of oxygen in the Hg-O layer, which then could affect the superconductivity of the material during the annealing process. It has been found that Tc can be increased by more than 20 K using an annealing temperature of 300 °C for 10 h, while annealing above 350 °C leads to loss of superconductivity due to Hg loss. Normal state-ρ tends to decrease with increasing annealing temperatures up to 400 °C. In addition, flattening in the normal state-ρ curves of doped samples indicated an increasingly insulating behavior.
| Original language | English |
|---|---|
| Pages (from-to) | 121-126 |
| Number of pages | 6 |
| Journal | Physica C: Superconductivity and its Applications |
| Volume | 313 |
| Issue number | 1-2 |
| DOIs | |
| State | Published - 1999 |
| Externally published | Yes |
Funding
This work is supported in part by US AFOSR and NSF EPSCOR funds. We also thank Y.Y. Xie for his valuable help in preparation of samples and we are very grateful to the Midwest Superconductivity for the use of their SQUID.