Long persistence red phosphors and method of making
AssigneeSarnoff Corporation
InventorsPerry Niel Yocom, Diane Zaremba
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Abstract
Long persistence phosphors based on strontium sulfide and activated with a divalent rare earth such as europium and a trivalent rare earth that does not change valence in a strontium sulfide host, and including oxygen and a halide, have long persistence and emit in the red-to-orange colors of the spectrum.
Claims29
A long persistence, red-emitting phosphor comprising the formula SrS:Eu:M.O.X wherein M is a trivalent rare earth that does not change valence in the SrS host, and X is a halogen.
A method of making a phosphor having the formula SrS:Eu:M.O.X wherein M is a trivalent rare earth that does not change valence in the SrS host and X is a halogen comprising
- a) mixing strontium sulfate doped with europium and one or more trivalent rare earths that does not change valence in a SrS host with a hydrocarbon and sulfur in a closed inert crucible;
- b) heating the mixture at about 900 to 1200° C. and
- c) heating the product with sulfur, a hydrocarbon and an ammonium halide to form SrS:Eu:M.O.X wherein M and X have the meanings given above.
A phosphor comprising a long persistence, red-emitting strontium sulfide doped with europium and a coactivator M where M is a rare earth ion selected from the group consisting of:
- praseodymium, neodymium, gadolinium, terbium, dysprosium, holmium, erbium and lutetium.
Dependencies are inferred from the claim text.