Alkali metal alkaline earth metal sulfate phosphor activated with cerium and terbium and lamp containing same
AssigneeGeneral Electric Company
InventorJacob G. Rabatin
Life of this patent
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Abstract
Mixed rare earth alkali and alkaline earth sulfates activated with cerium and terbium are used as a phosphor coating system for fluorescent lamps. The phosphor efficiently emits light in the green region and the emission spectrum of the phosphor demonstrates a prominent peak in the 520-560 nm region with minor inflections at other visible wavelengths.
Claims6
A luminescent material comprising crystals of:
- M.sub.w Ca.sub.x Ce.sub.y Tb.sub.z SO.sub.4
- wherein M = Lithium or sodium
- w = y + z
- x = 1 - (w + Y + z) >
- 0.3
- y = 0.05 to 0.25
- z = 0.05 to 0.20
- said material exhibiting relatively high quantum efficiencies for emissions in the visible green spectral region, when excited by 2537A radiation
A fluorescent lamp including a sealed glass envelope having means contained therein to generate 254 nm radiation and coated on an inner surface of said envelope a phosphor material comprising crystals of:
- M.sub.w Ca.sub.x Ce.sub.y Tb.sub.z SO.sub.4
- wherein M = lithium or sodium
- w = y + z
- x = 1 - (w+Y+z)>0.3
- y = 0.05 to 0.25
- z = 0.05 to 0.20
a method of phosphor preparation comprising the steps:
- a. blending a mixture of phosphor ingredients consisting essentially of:
- a. one salt from the group Li.sub.2 CO.sub.3, Na.sub.2 CO.sub.3
- b. CaCO.sub.3
- c. Ce(NO.sub.3).sub.3.sup.. 6H.sub.2 O
- d. Tb.sub.4 O.sub.7
- e. (NH.sub.4).sub.2 SO.sub.4
- in preselected amounts to form
- M.sub.w Ca.sub.x Ce.sub.y Tb.sub.z SO.sub.4
- wherein
- M = lithium or sodium
- w = y+z
- x = 1 - (w+y+z)>0.3
- y = 0.05 to 0.25
- z = 0.05 to 0.20
- b. and firing the blended mixture in a covered vessel at elevated temperatures in the range 300.degree.-500.degree. C for 1-2 hours.
Dependencies are inferred from the claim text.