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Process for Improving Properties of High Temperature Oxide Superconductors

IP.com Disclosure Number: IPCOM000035257D
Original Publication Date: 1989-Jun-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Gallagher, WJ: AUTHOR [+2]

Abstract

Mixed valance oxide high superconducting transition temperature superconductors achieve their metallic character by having a crystallographic structure whose ideal formula does not balance the negative valences of the oxygen atoms with the sum of the usual positive valences of the metals. This imbalance is compensated by the sum of two effects: (a) the presence of oxygen atom vacancies in the real lattice and (b) a fraction of one of the metals acquiring an unusual valence state. The latter effect controls the extent to which the allowed energy bands are filled and thereby profoundly effects the electrical properties of both the normal and of the superconducting state.

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Process for Improving Properties of High Temperature Oxide Superconductors

Mixed valance oxide high superconducting transition temperature superconductors achieve their metallic character by having a crystallographic structure whose ideal formula does not balance the negative valences of the oxygen atoms with the sum of the usual positive valences of the metals. This imbalance is compensated by the sum of two effects: (a) the presence of oxygen atom vacancies in the real lattice and (b) a fraction of one of the metals acquiring an unusual valence state. The latter effect controls the extent to which the allowed energy bands are filled and thereby profoundly effects the electrical properties of both the normal and of the superconducting state.

The concentration of oxygen atom vacancies in high Tc oxide superconductors was heretofore determined by conditions of equilibrium, i.e., the oxygen partial pressure during the preparation or during subsequent annealing of the materials. This concentration can also be varied by non-equilibrium means,
i.e., by exposing the oxide surface to some energetic form of oxygen, such as free atoms or metastable electronic excited states, at a temperature at which oxygen atoms can diffuse into the bulk, the material is then cooled to a temperature at which diffusion is not rapid enough for outdiffusion.

A simple means for doing this is to expose the mixed oxide superconductor samples held at an elevated temperature to a glow discharge...