NEUTRON AND X-RAY-INVESTIGATIONS ON THE OXYGEN BONDING IN YBA2CU3O(7-X) COMBINED WITH PHYSICOCHEMICAL METHODS

The occupancy of the oxygen lattice positions at different annealing c onditions in YBa2Cu3O(7-x) were determined by Rietveld refinements usi ng neutron and X-ray diffraction data. The occupation density for the oxygen positions O1 to O4 were ascertained. The values of the oxygen c ontent of the samples from this method were compared with those measur ed by thermoanalysis. The O1 and O4 oxygen atoms are exchangeable by t hermal treatment. The oxygen in the planes is fixed and can not be rem oved by thermal treatment up to 935-degrees-C. The binding strength of O1 in the lattice is stronger than that of O4 atoms; this is demonstr ated by a higher temperature of dissociation of the O1 atoms. The amou nt of the oxygen taken up is not exactly equal to the oxygen actually in the lattice positions. In the temperature region below 400-degrees- C adsorption and chemisorption processes are become dominant.