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Superconducting Oxyfluoride Films

IP.com Disclosure Number: IPCOM000034377D
Original Publication Date: 1989-Feb-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Gambino, RJ: AUTHOR [+3]

Abstract

High Tc superconductivity has been reported in bulk material with the approximate composition YBa2Cu3F2Oy, where y is about 6. Attempts to incorporate fluorine into these compounds by various methods of fluorination have not been very successful. This article provides a method of incorporating fluorine into thin films of these compounds and controllably removing excess fluorine over the stoichiometry required for good superconducting properties. Thin films were prepared by three-source electron beam evaporation using Cu and Y metals as sources of those elements and barium fluoride as the source of both Ba and F. The BaF2 was fired overnight at 900oC in air to outgas and sinter it. It was evaporated from a tungsten hearth liner.

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Superconducting Oxyfluoride Films

High Tc superconductivity has been reported in bulk material with the approximate composition YBa2Cu3F2Oy, where y is about 6. Attempts to incorporate fluorine into these compounds by various methods of fluorination have not been very successful. This article provides a method of incorporating fluorine into thin films of these compounds and controllably removing excess fluorine over the stoichiometry required for good superconducting properties. Thin films were prepared by three-source electron beam evaporation using Cu and Y metals as sources of those elements and barium fluoride as the source of both Ba and F. The BaF2 was fired overnight at 900oC in air to outgas and sinter it. It was evaporated from a tungsten hearth liner. The rates set on the feedback control system for the quartz crystal rate monitors were based on the deposition of Y2O3,BaF2 and CuO. The evaporation was carried out in 7x10-5 Torr O2 . The rates were adjusted to give the nominal composition YBa2Cu3O4.5F4 . The film was found to have the composition Y1.8Ba1.83Cu3OyF6.6 in the as- deposited state and the fluorine concentration was uniform through the thickness of the film. When these films are annealed in dry O2 they do not become conducting and superconducting as the oxide films do when prepared under similar conditions. In order to selectively remove F from the films in a controlled manner, high temperature hydrolysis is used. The sample is fired for sever...