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High temperature superconductors in the La/sub 1+x/Ba/sub 2-x/Cu/sub 3/O/sub y/ system

Conference ·
OSTI ID:5573694
In the La Ba Cu oxide system the La ions can substitute on the Ba sites due to a close match in the ionic radius of the two (as opposed to the Y Ba Cu oxide system). Thus it is possible to make a solid solution La/sub 1+x/Ba/sub 2-x/Cu/sub 3/O/sub y/ where O approx. x less than or equal to 0.5 and y approx. 7. Several compounds of this family have been made, and their synthesis and crystal structure are described. LaBa/sub 2/Cu/sub 3/O/sub y/ can be made under high pressure O/sub 2/. This phase is orthorhombic: as the La content increases. La substitutes on the Ba sites until for La/sub 1.5/Ba/sub 1.5/Cu/sub 3/O/sub 7.33/, 1/4 of the Ba are replaced by La (disordered). This substitution changes the crystal symmetry from orthorhombic to tetragonal. The transition temperature and the critical current for various members of this series are presented. In particular, it will be shown that the midpoint in this series, La/sub 1.25/Ba/sub 1.75/Cu/sub 3/O/sub y/. Is a tetragonal bulk superconductor. Effect of various heat treatments on the superconducting properties is also presented. 19 refs., 3 figs., 2 tabs.
Research Organization:
Du Pont de Nemours (E.I.) and Co., Wilmington, DE (USA). Central Research and Development Dept.; Brookhaven National Lab., Upton, NY (USA); Virginia Univ., Charlottesville (USA). Dept. of Physics
DOE Contract Number:
AC02-76CH00016
OSTI ID:
5573694
Report Number(s):
BNL-40757; CONF-871124-85; ON: DE88006367
Country of Publication:
United States
Language:
English