Transition-Metal Oxide Superconductivity
Abstract
Superconductivity in transition-metal oxides is discussed from the standpoints of electron transfer mechanisms and the transition from superconduction to normal conduction. As explanations for the reported superconducting effects, it is suggested that polarons associated with ion pairs of the d9 yields d8 ion combination in 180-degree bond geometries (e.g., Cu(2+) yields Cu(3+) + e(-) ion perovskites) and d1 yields d0 combination in 90-degree geometries (e.g., Ti(3+) yields Ti(4+) + e(-) in spinels) become itinerant within cell boundaries through energy-free electron transfers made possible by strong orbital exchange coupling. The proposed superconduction model is based on continuous linkages between cells that result in moving chains of uniformly spaced charge carriers. A phenomenological theory of normal resistivity and superconduction transition temperature as functions of composition for the La(2- x)Sr(x)CuO4 and YBa2Cu3O(y) perovskite families provides excellent agreement with experiment. Reported superconduction and structural data for the related Bi2(Sr,Ca)3Cu2O(8+y) system are also included. Optimized lattice ordering of the sources that produce the mixed-valence Cu(2+)(3+) ions could result in critical temperatures above 300 K. Keywords: Covalent bonding, Critical temperature, Magnetic exchange, Activation energy.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 20, 1988
- Accession Number
- ADA197069
Entities
People
- Gerald F. Dionne
Organizations
- Massachusetts Institute of Technology