Fluorescent substance and light-emitting device using the same
View Patent ↗An field effect transistor includes a first semiconductor region, a gate electrode insulatively disposed over the first semiconductor region, source and drain electrodes between which the first semiconductor region is sandwiched, and second semiconductor regions each formed between the first semiconductor region and one of the source and drain electrodes, and having impurity concentration higher than that of the first semiconductor region, the source electrode being offset to the gate electrode in a direction in which the source electrode and the drain electrode are separated from each other with respect to a channel direction, and one of the second semiconductor regions having a thickness not more than a thickness with which the one of second semiconductor regions is completely depleted in the channel direction being in thermal equilibrium with the source electrode therewith.
1. A method for manufacturing a fluorescent substance comprising:
mixing a raw material for Eu, a raw material for Si, at least one raw material powder of alkaline earth, and at least one selected from the group consisting of raw materials for La, Gd, Cs, and K to obtain a mixture of raw materials;
pre-firing the mixture for 1 to 3 hours in an air atmosphere at a temperature ranging from 500 to 700° C. to obtain a baked material;
mixing the baked material and firing for 3 to 7 hours in a reducing atmosphere consisting of a mixed gas of N 2 /H 2 at a temperature ranging from 1000 to 1600° C. to obtain a first fired product;
pulverizing the first fired product to obtain a pulverized first fired product;
placing the pulverized first fired product into a vessel;
placing the vessel housing the pulverized first fired product in a furnace;
purging the furnace with nitrogen gas in vacuum;
firing the pulverized first fired product for 2 to 6 hours in a reducing atmosphere consisting of N 2 /H 2 and having a hydrogen concentration of 5% to 100% at a temperature ranging from 1000 to 1600° C. to obtain a fluorescent substance consisting of an alkaline earth ortho-silicate.
2. The method according to claim 1 , wherein the raw material for Eu is Eu 2 O 3 powder.
3. The method according to claim 1 , wherein the raw material for Si is SiO 2 powder.
4. The method according to claim 1 , wherein the oxide raw material powder of alkaline earth comprises SrCO 3 powder.
5. The method according to claim 1 , wherein the oxide raw material powder of alkaline earth comprises CaCO 3 powder.
6. The method according to claim 1 , wherein the raw material for La is La 2 O 3 powder.
7. The method according to claim 1 , wherein the raw material for Gd is Gd 2 O 3 powder.
8. The method according to claim 1 , wherein the raw material for Cs is CsCl powder.
9. The method according to claim 1 , wherein the raw material for K is KCl powder.
10. The method according to claim 1 , further comprising adding a crystal growth-promoting agent to the mixture of raw materials.
11. The method according to claim 10 , wherein a content of the crystal growth-promoting agent is 0.5%-30% by weight based on an entire quantity of raw material powders.
12. The method according to claim 10 , wherein the crystal growth-promoting agent is selected from the group consisting of ammonium chloride, ammonium bromide, ammonium iodide, chloride of alkaline metal, bromide of alkaline metal, iodide of alkaline metal, chloride of alkaline earth metal, bromide of alkaline earth metal, and iodide of alkaline earth metal.
13. The method according to claim 1 , wherein the vacuum is 1000 Pa or less.
14. The method according to claim 1 , further comprising pulverizing the fluorescent substance to obtain a fluorescent particle.
15. The method according to claim 14 , further comprising sieving the fluorescent particle.
16. The method according to claim 15 , further comprising providing a surface-covering material on a surface of the fluorescent particle.
17. The method according to claim 16 , wherein the covering material is applied to the surface of the fluorescent particle by using a dispersion or solution of the covering material.
18. The method according to claim 17 , wherein the fluorescent particle is immersed in the dispersion or solution for a prescribed period of time and then dried by heating to deposit the covering material on the surface of the fluorescent particle.
19. The method according to claim 16 , wherein the surface-covering material is formed of at least one selected from the group consisting of silicone resin, epoxy resin, fluorinated resin, tetraethoxy silane, silica, zinc silicate, aluminum silicate, calcium polyphosphate, silicone oil, and silicone grease.
20. The method according to claim 16 , wherein the covering material is provided at a ratio of 0.1 to 50% by volume based on the volume of the fluorescent substance.