AN EFFECTIVE METHOD FOR AVOIDING CAHGO2 PHASE-FORMATION DURING SINTERING AND CRYSTALLIZATION OF THE HG-FAMILY SUPERCONDUCTORS UNDER HIGH GAS-PRESSURE

Here we report a few methods of avoiding formation of the CaHgO2 phase during annealing and crystallization of mercury based superconducting ceramics. These methods are based on the following principles: rapid temperature raise to pass the temperature range at which CaHgO2 easily forms, combined temperature and pressure quenching, diluting gas carr ier concentration and processing highly reactive fine-grain-size powde r made by the sol-gel method, The report is supported with observation s made by the XRD, SEM and high-pressure DTA methods. Some of the obse rved reactions between the crystallized HTS materials and the various crucible materials are reviewed. This is important because processing the mercury based HTS materials encounters problems caused by high rea ctivity of mercury vapours. It results in limited corrosion resistance of crucibles and substrate plates. The choice of BaZrO3 is suggested as the corrosion resistant crucible material.