Thermoelectric power and superconducting properties of Y_{1}Ba_{2}Cu_{3}O_{7-δ} and R_{1}Ba_{2}Cu_{3}O_{7-δ}

The high-$T_c$ superconductors $R_1$ ${\mathrm{Ba}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ (R denotes rare-earth elements) and ${\mathrm{Y}}_1$ ${\mathrm{Ba}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ are prepared in several different processes. ${\mathrm{Y}}_1$ ${\mathrm{Ba}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ prepared in flowing ${\mathrm{O}}_2$ and slowly cooled shows $T_c$=94 K, a lattice parameter ratio c/b=3.00 and negative thermoelectric power S, while quench-cooled ${\mathrm{Y}}_1$ ${\mathrm{Ba}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ shows reduced $T_c$, an elongated structure along the c axis with c/b=3.02, and positive S. Most of the rare-earth-element superconductors show $T_c$ near or higher than 90 K. Rare-earth-element superconductors with the rare-earth-element ionic radius larger than 0.92 Å show positive S, while those with the ionic radius smaller than 0.92 Å show negative S. These experimental results seem to indicate a close correlation between the structural strain and the superconducting properties.