Coating processes – Electrical product produced – Fluorescent or phosphorescent base coating
Patent
1989-10-02
1990-05-15
Cooper, Jack
Coating processes
Electrical product produced
Fluorescent or phosphorescent base coating
2523014R, 2523014F, 427219, C09K 1179
Patent
active
049257021
ABSTRACT:
A process is disclosed for producing M' phase YTaO.sub.4 :Nb X-ray phosphor which comprises forming a mixture of components Y.sub.2 O.sub.3, Ta.sub.2 O.sub.5, and Nb.sub.2 O.sub.5, and a flux which can be lithium chloride, lithium sulfate or a mix of lithium sulfate and potassium sulfate in an 80 to 20 mole ratio, the flux making up about 25% to 50% by weight of the mixture, the components being provided in stoichiometric amounts to form the phosphor, firing the mixture in a furnace by heating to a temperature of about 1200.degree. C. to 1300.degree. C. at a heating rate of about 1.0.degree. C./min. to 1.5.degree. C./min. and maintaining the temperature for about 10 to 14 hours to react the components and produce luminescent material, cooling the material by turning off the heat to the furnace and allowing the material to remain therein until the temperature is no higher than about 300.degree. C., washing with deionized water, removing the wash water and drying, and classifying to obtain a -325 mesh particle size, forming a uniform blend of the phosphor and silicon dioxide wherein the amount of silicon dioxide is about 0.01% to 0.1% by weight, and wherein the silicon dioxide has a particle size of less than about 1 micrometer in diameter, and dry milling to produce a silicon dioxide coated phosphor having a bulk density of at least about 50% greater than the phosphor produced absent the coating and a luminescence improvement of at least about 4% over the phosphor produced absent the coating.
REFERENCES:
patent: 3459674 (1969-08-01), Emoto et al.
patent: 4024069 (1977-05-01), Larach
patent: 4225653 (1980-09-01), Brixner
patent: 4690832 (1987-09-01), Yale
patent: 4707635 (1987-11-01), Tateyama et al.
patent: 4717590 (1988-01-01), Wolfe et al.
Brixner & Chen (J. Electrochemical Soc., 130 (12), 1983, 2435-43), "On the Structural and Luminescent Properties of the M'LnTaO.sub.4 Rare Earth Tantalates".
Cooper Jack
GTE Products Corporation
Quatrini L. Rita
Walter Robert E.
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