Thermoelectric power and superconducting properties of Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-//sub delta/ and R/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-//sub delta/

The high-T/sub c/ superconductors R/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-//sub delta/ (R denotes rare-earth elements) and Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-//sub delta/ are prepared in several different processes. Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-//sub delta/ prepared in flowing O/sub 2/ and slowly cooled shows T/sub c/ = 94 K, a lattice parameter ratio c/b = 3.00 and negative thermoelectric power S, while quench-cooled Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-//sub delta/ shows reduced T/sub c/, an elongated structure along the c axis with c/b = 3.02, and positive S. Most of the rare-earth-element superconductors show T/sub c/ near or higher than 90 K. Rare-earth-element superconductors with the rare-earth-element ionic radius larger than 0.92 A show positive S, while those with the ionic radius smaller than 0.92 A show negative S. These experimental results seem to indicate a close correlation between the structural strain and the superconducting properties.