High-Tcsuperconductivity in regions of possible compound formation:Y2−xBaxCuO4−x/2+δandY2−xBa1+xCu2O6−x/2+δ

High-${T}_{c}$ superconductivity is investigated in the Y-Ba-Cu-O system. Regions of possible compound formation are ${\mathrm{Y}}_{2\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Ba}}_{\mathrm{x}}$${\mathrm{CuO}}_{4\mathrm{\ensuremath{-}}\mathrm{x}/2+\mathrm{\ensuremath{\delta}}}$ and ${\mathrm{Y}}_{2\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Ba}}_{1+\mathrm{x}}$${\mathrm{Cu}}_{2}$${\mathrm{O}}_{6\mathrm{\ensuremath{-}}\mathrm{x}/2+\mathrm{\ensuremath{\delta}}}$. ${T}_{c}$ values g90 K are found for the former with x=0.8 (the Chu material) and for the latter with x=0.2 and may imply a common superconductivity phase in both samples. Critical fields determined by resistance and low-field ${d}_{c}$ susceptibility measurements are reported.