DIRECT OBSERVATION OF MICROSCOPIC INHOMOGENEITIES WITH ENERGY-DISPERSIVE DIFFRACTION OF SYNCHROTRON-PRODUCED X-RAYS

Evidence of structural inhomogeneities in two high-transition-temperat ure superconductors, YBa2CU3O7-delta and Nd2-xCexCuO4-y, is presented. When samples were illuminated by highly collimated x-rays produced on a synchrotron wiggler, small changes in the lattice were detected ove r a spatial scale of 10 micrometers. These changes are interpreted as evidence of variations in the oxygen content in one case and in the ce rium content in the other; both affect the superconducting properties. The existence of such structural inhomogeneities brings into question whether exotic experimental results obtained from superconducting mat erials with high transition temperatures actually reflect intrinsic pr operties.