Process for producing cerium activated yttrium gallium aluminate

Details Process for producing cerium activated yttrium gallium aluminate Process for producing cerium activated yttrium gallium aluminate

1990-11-01

1991-12-31

Cooper, Jack

Compositions

Inorganic luminescent compositions

Compositions containing halogen; e.g., halides and oxyhalides

C09K 1180

Patent

active

050769642

ABSTRACT:
A process for producing cerium activated yttrium gallium aluminate phosphor comprises dry blending yttrium oxide, gallium oxide, cerium oxide, and unmilled aluminum hydroxide wherein the aluminum hydroxide is a small particle size aluminum hydroxide wherein the 50% size as measured by Coulter Counter 2 minute stir technique using about a 100 micrometer aperture is about 10.8.+-.5 micrometers in diameter and by Coulter Counter 5 minute sonic technique using about a 100 micrometer aperture is about 9.3.+-.3 micrometers in diameter to form a uniform mixture thereof, and firing the mixture in air at a temperature of about 1550.degree. C. to about 1625.degree. C. for about 4 hours to 8 hours to produce a once-fired phosphor wherein the brightness is at least about 24% higher than phosphors produced using milled aluminum hydroxide that is large in particle size than the small size aluminum hydroxide. By refiring the phosphor, the brightness is further increased by at least about 14% over the once-fired phosphor. When the firing temperature is about 1625.degree. C. to 1700.degree. C. the brightness of the once-fired phosphor is increased by at least about 34% over phosphors produced using larger particle size aluminum hydroxide. In the latter case, the refired phosphor is at least about 10% brighter than the once-fired phosphor.

REFERENCES:
patent: 4246630 (1981-01-01), Wolfe
patent: 4479886 (1984-10-01), Kasenga
patent: 4818433 (1989-04-01), Sigai et al.

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