Phosphor composition

• US 9,428,688 B2
• Filed: 11/17/2008
• Issued: 08/30/2016
• Est. Priority Date: 11/17/2008
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Collins, Brian T., Hussell, Christopher P., Emerson, David T., Le Toquin, Ronan P.
• Primary Examiner(s): Choi, Ling
• Assistant Examiner(s): Miller, David L.
• Application Number:
  US12/271,945
• Publication Number:
  US 20100123104A1
• Time in Patent Office: 2,843 Days
• Field of Search: 252/586, 252/301.4 R, 252/301.4 F, 252/301.6 F, 252/301.6 R, 313/485, 313/486, 313/503, 313/512, 423/263, 257/98, 257/100, 257/E33.061, 257/78, 428/690, 345/37, 345/41, 345/45, 345/47, 345/60, 345/75, 345/76
• US Class Current: 1/1
• CPC Class Codes: C04B 2235/3224 Rare earth oxide or oxide forming salts thereof, e.g. scandium oxide
• CPC Class Codes: C04B 2235/3852 Nitrides, e.g. oxynitrides, carbonitrides, oxycarbonitrides, lithium nitride, magnesium nitride
• CPC Class Codes: C04B 2235/3865 Aluminium nitrides
• CPC Class Codes: C04B 2235/3869 Aluminium oxynitrides, e.g. AlON, sialon
• CPC Class Codes: C04B 2235/3873 Silicon nitrides, e.g. silicon carbonitride, silicon oxynitride
• CPC Class Codes: C04B 2235/445 Fluoride containing anions, e.g. fluosilicate
• CPC Class Codes: C04B 35/58 based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides containing free binder metal C22C29/00
• CPC Class Codes: C04B 35/581 based on aluminium nitride
• CPC Class Codes: C04B 35/584 based on silicon nitride
• CPC Class Codes: C04B 35/591 obtained by reaction sintering
• CPC Class Codes: C04B 35/593 obtained by pressure sintering
• CPC Class Codes: C04B 35/5935 obtained by gas pressure sintering
• CPC Class Codes: C04B 35/597 based on silicon oxynitride, e.g. SIALONS
• CPC Class Codes: C09K 11/025 non-luminescent particle coatings or suspension media
• CPC Class Codes: C09K 11/0883 Arsenides; Nitrides; Phosphides
• CPC Class Codes: C09K 11/7728 containing europium
• CPC Class Codes: C09K 11/77348 Silicon Aluminium Nitrides or Silicon Aluminium Oxynitrides
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps

Abstract

A method is disclosed for forming a blended phosphor composition. The method includes the steps of firing precursor compositions that include europium and nitrides of at least calcium, strontium and aluminum, in a refractory metal crucible and in the presence of a gas that precludes the formation of nitride compositions between the nitride starting materials and the refractory metal that forms the crucible. The resulting compositions can include phosphors that convert frequencies in the blue portion of the visible spectrum into frequencies in the red portion of the visible spectrum.

Claims

1. A method of making a phosphor composition, the method comprising:

forming a powder mixture comprising Ca₃N₂, Sr₂N, AlN, Si₃N₄ and

a europium source composition;

heating the powder mixture at or near atmospheric pressure in the presence of a forming gas mixture comprising nitrogen and hydrogen; and

forming from the powder mixture a first phase comprising a nitride phosphor having a nominal composition of Ca_1-x-ySr_xEu_yAlSiN₃, where 0<

x<

1 and 0<

y<

1, and a second phase comprising silicon aluminum oxynitride.

2. The method according to claim 1 comprising:

heating the powder mixture in a refractory crucible that is substantially inert in the presence of the forming gas mixture for a time sufficient to produce a phosphor composition that will down convert photons in the blue and ultraviolet regions of the spectrum into photons in the longer wavelength regions of the visible spectrum.

3. The method according to claim 1, comprising heating the powder mixture at atmospheric pressure.

4. The method according to claim 1, wherein the powder mixture is heated to a temperature of between about 1500 to 180°

C.

5. The method according to claim 1 wherein the silicon aluminum oxynitride comprises Si₂Al₄O₄N₄.

6. The method according to claim 1 wherein the forming gas mixture comprises between about 5% and 10% hydrogen and a balance nitrogen.

7. The method according to claim 1 wherein x is between about 0.5 and 0.7.

8. The method according to claim 7 wherein x is between about 0.55 and 0.67.

9. The method according to claim 1 wherein y is between about 0.013 and 0.017.

10. The method according to claim 1 wherein the forming gas mixture includes about 95% nitrogen and about 5% hydrogen.

11. The method according to claim 1 wherein the heating is carried out at a temperature of 1750°

C.

12. The method according to claim 1 wherein the heating comprises at least three heating steps at increasingly higher temperatures.

13. The method according to claim 12 comprising a first heating step at 800°

C., a second heating step at 1200°

C., and a third heating step above 1600°

C.

14. The method according to claim 13 wherein ramping steps of about 350°

C. per hour are employed between the first, second and third heating steps.

15. The method according to claim 13 wherein the first and second heating steps are carried out for one hour each, and wherein the third heating step is carried out for two hours.