The role of CuO chain length on superconductivity emergence in YBa2Cu3O6.30

The authors investigate the tetragonal(T)-orthorhombic(O) transient zone of YBa2Cu3O6+x, in a comparative way on pair samples one of which is produced by deintercalation [D] and the other by intercalation [I] of intrinsic oxy gen in the basal Cu(1)O-x plane and having the same oxygen content (k) and thermal history. Resistive and electron diffraction measurements, performed on [D](k)-[I](k) pairs within the composition range 0.28 less than or equa l to k less than or equal to 0.32, are reported. Direct evidence is provide d that the T-OII transient is a structural and electronic two phase region characterized by the (T + OII)[D](0.30) nonsuperconducting (non-SC) and (OI I + OIII*)[I](0.30) superconducting (SC) phases. The OII superstructure rep resents the minority component of [D]0.30 phase and the majority one of [I] (0.30) and OIII* is a new orthorhombic anti-OIII superstructure. The nature of the non-SC and SC behaviours has been comparatively investigated by NQR analysis at the T-OII borderline. The evaluated different values of the av erage chain lengths emphasize the role of the Cu-O chain length on the hole doping efficiency in YBCO at constant oxygen content.