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Electrodrift purification of materials for room temperature radiation detectors

United States Patent

5,641,392
June 24, 1997
View the Complete Patent at the US Patent & Trademark Office
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A method of purifying nonmetallic, crystalline semiconducting materials useful for room temperature radiation detecting devices by applying an electric field across the material. The present invention discloses a simple technology for producing purified ionic semiconducting materials, in particular PbI.sub.2 and preferably HgI.sub.2, which produces high yields of purified product, requires minimal handling of the material thereby reducing the possibility of introducing or reintroducing impurities into the material, is easy to control, is highly selective for impurities, retains the stoichiometry of the material and employs neither high temperatures nor hazardous materials such as solvents or liquid metals. An electric field is applied to a bulk sample of the material causing impurities present in the sample to drift in a preferred direction. After all of the impurities have been transported to the ends of the sample the current flowing through the sample, a measure of the rate of transport of mobile impurities, falls to a low, steady state value, at which time the end sections of the sample where the impurities have concentrated are removed leaving a bulk sample of higher purity material. Because the method disclosed here only acts on the electrically active impurities, the stoichiometry of the host material remains substantially unaffected.
James; Ralph B. (Livermore, Alameda County, CA), Van Scyoc, III; John M. (Plainfield, Cumberland County, PA), Schlesinger; Tuviah E. (Mt. Lebanon, Allegheny County, PA)
08/ 504,001
July 19, 1995
STATEMENT OF GOVERNMENT INTEREST This invention was made with Government support under contract no. DE - AC04 - 94AL8500 awarded by the U.S. Department of Energy to Sandia Corporation. The Government has certain rights in the invention.