Structural and charge-transfer description of high-T/sub c/ superconductivity in Y1Ba2Cu3O/sub 7-δ/

The observation of high-T/sub c/ superconductivity is described in terms of the unique structure of the ceramic Y1Ba2Cu3O/sub 7-δ/ and treated as a special defect case of the A2BX4 archtypes normally represented by K2MnF4 or K2NiF4. The recently elucidated structure of the ceramic superconductor (known as the 1-2-3 material) can be shown to be a substitutive distortion defect modification of the well-known antiferromagnetic K2NiF4 structure if it is written in the defect A4B2X8 form (Ba22+ Cu22+)(Y13+ Cu13+)O/sub 8-w/. This material is superconducting for 1 < w < 1.5. The presence of the corner Cu3+ in the basal planes of the 1-2-3 unit cell coupled with the linking region of an oxygen-vacancy, capable of forming an F center, and further influenced by the distorted square planar coordinated oxygens of the corner copper ions (CuO3 units) allows for a mediation of BCS theory via exciton interactions, and influenced by a Jahn-Teller distortion. The edge Cu2+ ions are hybridized in CuO2 layers, and the five-fold coordination allows for a shared oxygen ion with the corner copper ions establishing an interactive element between a-b plane and the z axis