Cominco, Ltd.

Comino Ltd.

Cominco Electronic Materials Inc.

Robert W Smyth

John Alden Dunlop

Gerald W Toop

Edward Francis Milner

Horst E Hirsch

Lead with a low alpha particle emission is produced by selecting an orebody wherein lead mineral is present in a coarsely disseminated form and substantially free of impurities. The ore is selected from a host rock that is relatively low in alpha emitters, such as a carbonate rock. The ore is mined and is milled such that the lead mineral can be separated from the host rock and any other minerals. The ground ore may be screened into one or more fractions having a narrow range of particle sizes. Each fraction is formed into a fluid suspension, and each suspension is subjected to gravity separation to remove the host rock and any other minerals which substantially contain the alpha particle-emitting substances, and to recover the lead mineral as a concentrate with a low alpha count. The lead concentrate is subjected to a suitable reduction operation that may include a conversion of the concentrate into a reducible form, without the introduction of alpha emitters, for the recovery of a low alpha lead. When the lead mineral is galena, suitable reductions include the smelting with sodiuim carbonate with or without an oxygen-bearing gas and electrolytic reduction in a molten bath of lead chloride. The low alpha lead recovered from these operations has an alpha count of about 0.02 alpha particle per cm.sup.2 per hour or less, and the count does not substantially increase with time. The recovered low alpha lead may be further purified by electro-refining.

Method for making low alpha count lead

Lead with a low alpha particle emission is produced by selecting an orebody wherein lead mineral is present in a coarsely disseminated form and substantially free of impurities. The ore is selected from a host rock that is relatively low in alpha emitters, such as a carbonate rock. The ore is mined and is milled such that the lead mineral can be separated from the host rock and any other minerals. The ground ore may be screened into one or more fractions having a narrow range of particle sizes. Each fraction is formed into a fluid suspension, and each suspension is subjected to gravity separation to remove the host rock and any other minerals which substantially contain the alpha particle-emitting substances, and to recover the lead mineral as a concentrate with a low alpha count. The lead concentrate is subjected to a suitable reduction operation that may include a conversion of the concentrate into a reducible form, without the introduction of alpha emitters, for the recovery of a low alpha lead. When the lead mineral is galena, suitable reductions include the smelting with sodium carbonate with or without an oxygen-bearing gas and electrolytic reduction in a molten bath of lead chloride. The low alpha lead recovered from these operations has an alpha count of about 0.02 alpha particle per cm.sup.2 per hour or less, and the count does not substantially increase with time. The recovered low alpha lead may be further purified by electro-refining.

Lead with a low alpha particle emission is produced by selecting an orebody wherein lead mineral is present in a coarsely disseminated form and substantially free of impurities. The ore is selected from a host rock that is relatively low in alpha emitters, such as a carbonate rock. The ore is mined and is milled such that the lead mineral can be separated from the host rock and any other minerals. The ground ore may be screened into one or more fractions having a narrow range of particle sizes. Each fraction is formed into a fluid suspension, and each suspension is subjected to gravity separation to remove the host rock and any other minerals which substantially contain the alpha particle-emitting substances, and to recover the lead mineral as a concentrate with a low alpha count. The lead concentrate is subjected to a suitable smelting operation, without the introduction of alpha emitters for the recovery of a low alpha lead. When the lead mineral is galena, the smelting is preferaby carried out with sodium carbonate and an oxygen-bearing gas in the presence of sodium chloride as a fluxing agent to form a low melting point slag. The low alpha lead has an alpha count of about 0.02 alpha particles per cm.sup.2 per hour or less, and the count does not substantially increase with time.

Embodiments of a method are disclosed for producing large size cadmium mercury telluride (CMT) sputtering targets of a homogeneous composition. Sputtering targets of CMT having a general formula Cd.sub.x Hg.sub.1-x Te wherein x has values in the range of about 0.14 to 0.60 are prepared by compacting finely divided CMT of a particle size smaller than 150.mu. in a die into a coherent compact having a density of at least 97% theoretical density. CMT with an x value of about 0.14 to about 0.20 preferably is compacted at a die preheat temperature of about 100 to 300.degree. C. and at a compacting pressure of at least about 400 MPa. CMT having an x value of about 0.20 to about 0.60 preferably is compacted at a die preheat temperature of about 300.degree. C. and a compacting pressure of about 160 to 275 MPa. The die may be evacuated to a pressure of less than about 133 Pa absolute prior to compacting.

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Trail, Canada

Robert W Smyth