T-O, OII-OIII and OIII-OI phase boundary in oxygen-chain-equalized and order-stabilized polycrystalline pair samples of YBa{sub 2}Cu{sub 3}O{sub 6+x}
- Univ. di Parma (Italy). Dipt. di Chimica Generale ed Inorganica
- Univ. di Cagliari, Monserrato (Italy)
- CNR-LAMEL, Bologna (Italy)
A comparative investigation, performed on Oxygen-Chain-equalized(k) Deintercalated [OCD]{sub k} and Intercalated [OCI]{sub k} pair-samples (k-pairs) of YBa{sub 2}Cu{sub 3}O{sub 6+x} by resistive {Tc} and electron diffraction (ED) at steps {Delta}k = 0.02--0.03, revealed that equivalent or non-equivalent microscopic oxygen-chain arrangements are produced, at the same oxygen content k, by intercalation and deintercalation of oxygen in the Cu(1)O{sub x} chains. These arrangements manifest in {Tc}-singularities or {Tc}-splittings of the k-pairs, whose occurrence can be straightforwardly explained by taking into account the non equivalence of the structural phase diagrams of YBCO, pointed out by electron diffraction, when produced by intercalation of oxygen in the tetragonal T structure or by deintercalation from the orthorhombic OI structure. {Tc}-singularities are produced in the k ranges for which a superimposition of the phase diagrams occurs, whereas {Tc}-splittings are pointed out in correspondence of split structural regions. The maximum {Tc}-splitting is observed in proximity of the semiconductor-metal transition with the appearing of superconductivity related to an anti-OIII (OIII{sup *}) superstructure in intercalated samples at k = 0.30, where the corresponding deintercalated samples are tetragonal and semiconductor. This result confirms that the vanishing of the antiferromagnetic ordering, the emergence of hole doped superconductivity and the symmetry breaking at the T-O transition are nearly coincident phenomena in YBCO. However, the related critical oxygen stoichiometry is strictly dependent on the ordering parameter in the Cu(1) plane, i.e., on the formation of extended chains. The OIII{sup *} structure, for the first time observed in a systematic way at the T-O transition in intercalated samples, seems to exhibit in analogy with OII and OIII a characteristic {Tc}.
- OSTI ID:
- 687416
- Report Number(s):
- CONF-9810174-; ISSN 0217-9792; TRN: 99:010371
- Journal Information:
- International Journal of Modern Physics B, Vol. 13, Issue 9-10; Conference: 9. national congress on high temperature superconductivity (SATT9), Ravenna (Italy), 6-9 Oct 1998; Other Information: PBD: 20 Apr 1999
- Country of Publication:
- United States
- Language:
- English
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