MICROWAVE-ABSORPTION CHARACTERIZATION OF THE YBA2CU3O7-DELTA HIGH-TEMPERATURE SUPERCONDUCTOR PREPARED BY DIFFERENT SINTERING AND OXYGEN ANNEALING TIMES

Low-field microwave absorption (LFMA) has been used to characterize and monitor subtle structural changes produced during the sintering and oxygen annealing process in the preparation of high-temperature superconductors such as YBa2Cu3O7-delta. LFMA measurements are compared with Meissner effect and resistance measurements and to the sample morphology. The LFMA technique as a probe is found to be more sensitive and discriminatory. It allows for an accurate determination of the onset transition temperature and is sensitive to identify multi-superconducting phases. Oxygen stoichiometry, grain size and inter-, intra-granular contacts are found to affect the LFMA intensity.