HgBa2CuO4+δ (Hg-1201) samples synthesized with various initial compositions and at different Hg vapor pressures were examined by SEM, TEM, EDS and X-ray diffraction. The results suggest that Hg-1201 is intrinsically a Hg non-stoichiometry phase. The allowed Hg vapor pressure, which is limited by the competitions from HgBaO2, required an equilibrium defect density in the Hg site at synthesis temperatures. These defects correspond to a 30% Hg deficiency at ∼800°C with a balance Hg vapor pressure at the order of 10-1 atm. However, the equilibrium defect density should decrease with temperature, and is approximately zero at room temperature based on our EDS data. Therefore, cation diffusion, defect coarsening, and possible phase segragation occur during the cooling, which create various impurities and inclusions in the samples obtained. Further investigations on the related phase diagrams are needed to design a better synthesis procedure.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Energy Engineering and Power Technology
- Electrical and Electronic Engineering