A contribution to the study of the Hg-Ba-Cu-O system

This work aims to contribute to the study of the Hg-Ba-Cu-O diagram. Generally, we can see that high-temperature superconductor phase diagrams are far from complete. Of these, the Hg-Ba-Cu-O diagram is very interesting owing to the high mercury fugacity. However, to study this diagram it is necessary to control both the mercury and the oxygen activities. The importance of this check is evident in the preparation of single-phase samples, where competitive phases are often obtained; knowledge of these phases will provide an improvement. Even the famous superconductor phase HgBa2CuO4+delta is still the subject of discussion. To study these compounds, thermogravimetric and differential thermal analyses, X-ray diffractometry, scanning electron microscopy and oxygen titration are the most important analyses. In particular, we applied the well known effusion technique, a programmed decomposition by the saturated vapour method, rarely used for this purpose.