Method for making small particle red emitting phosphors
AssigneeMatsushita Electric Industrial Co., Ltd.
InventorRavilisetty P. Rao
Life of this patent
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Abstract
Yttrium, gadolinium borate phosphor particles are produced by thermal decomposition of a xerogel or an aerogel including Rare Earth (yttrium, gadolinium and europium) and Alkaline Earth (barium, strontium, calcium, magnesium) salts. A sol-gel method is used and an organic precursor such as trimethyl borate obtains the respective xerogel or aerogel. Thermal decomposition of the gel takes place at a temperature well below the normal temperature of solid state reaction synthesis. The brightness of the final phosphor is improved by 5 to 10 by mixing the gel powder with respective nitrates thereof prior to calcination. The phosphor has the empirical formula: (Y1−x−y−z EuxGdy Mz)BO3 wherein: 0.01≦x≦0.1, 0≦y≦0.5, M=Ba/Sr/Ca/Mg and z≦0.1.
Claims16
A method of forming a europium activated yttrium, gadolinium borate phosphor having the empirical formula:
- (Y1−x−y−zEuxGdyMz) BO3
- wherein:
- 0.01≦x≦0.1, 0≦y≦0.5, M=Ba, Sr, Ca, Mg and z≦0.1;
- said method comprising the steps of:
- a) reacting a dilute solution comprising a source of yttrium, a source of gadolinium, a source of an alkaline earth element (i.e., barium or strontium or calcium or magnesium), a source of europium and an organic precursor providing a source of boron, in an acid medium to form a dilute gel;
- b) converting said dilute gel into a xerogel or an aerogel;
- c) adding a quantity of nitrates of said rare earth elements and said alkaline earth element reacted in step (a);
- and
- d) thermally decomposing the xerogel or aerogel and quantity of nitrates at a temperature below a solid state reaction temperature to obtain said phosphor.
A europium activated yttrium, gadolinium, alkaline earth borate phosphor having the empirical formula:
- (Y1−x−y−zEuxGdyMz) BO3
- wherein:
- 0.01≦x≦0.1, 0≦y≦0.5, M=Ba, Sr, Ca, Mg and z≦0.1;
- said phosphor produced by the steps of:
- a) reacting a dilute solution comprising a source of yttrium, a source of gadolinium, a source of an alkaline earth element(i.e., barium or strontium or calcium or magnesium), a source of europium and an organic precursor providing a source of boron, in an acid medium to form a dilute gel;
- b) converting said dilute gel into a xerogel or an aerogel;
- c) adding a quantity of nitrates of said rare earth elements and asaid alkaline earth element reacted in step (a);
- and
- d) thermally decomposing the xerogel or aerogel and quantity of nitrates at a temperature below a solid state reaction temperature to obtain said phosphor.
Dependencies are inferred from the claim text.