Oxygen order and charge-transfer mechanism in Zn-doped ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$

The structural and electronic properties of ${\mathrm{YBa}}_2$(${\mathrm{Cu}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Zn}}_{\mathit{x}}$ ${)}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ have been investigated as a function of δ and at 0≤x≤0.05. The oxygen-deficient compounds were obtained with the low-temperature Zr-gettering technique. It was found that the structural characteristics and anomalies, and the oxygen-ordering phenomena, observed in undoped ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$, also occur in Zn-doped compounds at the same oxygen concentration, although they are not related to the corresponding electronic features. This seems to suggest that the charge-transfer mechanism, controlling ${\mathit{T}}_{\mathit{c}}$ in pure ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$, is modified by the presence of Zn.