Preparation, Structure, Transport Properties and Photoemission Studies of the High-Tc-Superconductors YBa2Cu3O4-δ and La1-xSrxCuO4

Single-phase bulk-YBa 2 Cu 3 O 9-δ was prepared by solid-state reaction under oxygen atmosphere as well as exclusively in air, observing a transition from semi- to superconducting behaviour depending on the preparation. Low temperature powder x-ray diffraction from 300K down to 10K was carried out to investigate the structure. The upper critical field is estimated to B c2 (T=0) = 110T (T c -midpoint), critical current densities of up to 180A/cm 2 are determined at different temperatures in magnetic fields up to 7T. Photoemission experiments show, that grains are only coupled by semiconducting interfaces and reveal a strong hybridization between O-2p and Cu-3d states.