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. Genera lly, 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 necessar y to control both the mercury and the oxygen activities. The importance of this check is evident in the preparation of single-phase samples, where com petitive phases are often obtained; knowledge of these phases will provide an improvement. Even the famous superconductor phase HgBa2CuO4+delta is sti ll the subject of discussion. To study these compounds, thermogravimetric a nd differential thermal analyses, X-ray diffractometry, scanning electron m icroscopy and oxygen titration are the most important analyses. In particul ar, we applied the well known effusion technique, a programmed decompositio n by the saturated vapour method, rarely used for this purpose.