THE INFLUENCE OF WEAKLY BONDED OXYGEN ON THE CRYSTAL-STRUCTURE, ELECTRICAL AND RELAXATION PROPERTIES OF HTSC YBA2CU3O7-DELTA CERAMICS

Results are reported from studies of crystal structure, superconductiv ity, electrical resistance and internal friction of high-T-c Y Ba2Cu3O 7-delta ceramics (6.05 less than or equal to 7-delta less than or equa l to 6.95). The temperature dependence of internal friction Q(-1)(T) e xhibits the peaks at, 200-400 degrees C, which are due to the diffusio n of oxygen atoms at O4 and O5 sites. Ortho-tetra and orthoI-orthoII p hase transitions as well as the jumps of elastic moduli at 6.3 less th an or equal to 7-delta less than or equal to 6.5, associated with phas e transitions, have been observed.