High temp. yttrium barium copper oxide superconductor prodn. - from yttria, hydrated barium hydroxide and copper oxide by two=stage firing process

摘要

Prodn. of YBa2Cu3O7-x high temp. superconductor material comprises (a) intensively grinding and mixing Y2O3, hydrated Ba(OH)2 contg. max. 2.5 mol. H2O per mol. Ba(OH)2, and CuO; (b) firing the compacted material by heating at 80-100 deg. C/hr. from ambient temp. to 880-900 deg. C to drive off any CO2 combined as carbonate in the material, heating to 920-950 deg. C, holding at this temp. for 5-15 hrs. and then cooling, the cooling rate being 25-60 deg./hr. down to 500 deg. C; and (c) intensively mixing and crushing the material, pressing at 500-1000 bars and re-firing by heating to 935-945 deg. C, holding at this temp. for 15-25 hrs. and cooling, the cooling rate being 250-60 deg. C/hr. down to 500 deg. C.. Steps (b) and (c) are carried out in the presence of O2 at least between reaching 880 deg. C during heating and reacting 200 deg. C during cooling. ADVANTAGE - The superconductor material has high homogeneity and thus an attainable high critical temp. (92K), as well as an extremely low carbon content (below 0.02).