Osram Sylvania Inc.

Anthony L Diaz

Charles F Chenot

Shelley A Sonner

Jenace A Yurchisin

A novel phosphate treated silicate phosphor has been invented that exhibits improved lumen maintenance with respect to the untreated phosphor when used in a fluorescent lamp. In one aspect, a protective phosphate-containing surface layer is formed by treating the phosphor in an aqueous phosphate solution, filtering, and annealing. In particular, a BaSi,O,:Pb phosphor that has been treated in this way exhibits improved maintenance in a fluorescent lamp and a characteristic X-ray diffraction pattern evidencing the presence of the protective phosphate-containing surface layer.

Phosphate treated silicate phosphor

A cation-treated silicate phosphor and fluorescent lamp made therefrom are provided wherein the 100 hour radiance maintenance is significantly improved. The cation treatment method involves adding an amount of a silicate phosphor to a salt solution containing a cation wherein the ratio of cation to phosphor in the solution is from about 1:2 to about 4:1 moles of cation to moles of phosphor. The solution is then stirred for a time sufficient to cause the cation to attach to the phosphor surface to form a cation-treated phosphor. The cation-treated phosphor is separated from the solution and annealed at a temperature and for a time sufficient to increase radiance maintenance of the cation-treated phosphor.

Cation-treated silicate phosphor

A CaSiO.sub.3 :Pb,Mn phosphor is synthesized using a colloidal silica suspension wherein a cationic species is added to the suspension to form a well-mixed, easily-filtered, raw blend which reduces the filtering and calcining times required to produce a commercial quality phosphor.

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Athens, PA, United States of America

Anthony L Diaz