Long-persistence blue phosphors

• US 6,117,362 A
• Filed: 11/06/1998
• Issued: 09/12/2000
• Est. Priority Date: 11/07/1997
• Status: Expired due to Term

• Current Assignee: The University of Georgia Research Foundation, Inc., University of Puerto Rico
• Original Assignee: The University of Georgia Research Foundation, Inc., University of Puerto Rico
• Inventors: Yen, William M., Jia, Weiyi, Yuan, Huabiao, Lu, Lizhu
• Primary Examiner(s): KOSLOW, CAROL M
• Application Number:
  US09/187,944
• Time in Patent Office: 676 Days
• Field of Search: 252/301.4 R, 117/946, 117/950
• US Class Current: 252/301.40R
• CPC Class Codes: C09K 11/7734 Aluminates
• CPC Class Codes: C30B 29/22 Complex oxides

Abstract

This invention relates to phosphors including long-persistence blue phosphors. Phosphors of the invention are represented by the general formula:

MO . mAl.sub.2 O.sub.3 :Eu.sup.2+,R.sup.3+

wherein m is a number ranging from about 1.6 to about 2.2, M is Sr or a combination of Sr with Ca and Ba or both, R³⁺ is a trivalent metal ion or trivalent Bi or a mixture of these trivalent ions, Eu²⁺ is present at a level up to about 5 mol % of M, and R³⁺ is present at a level up to about 5 mol % of M. Phosphors of this invention include powders, ceramics, single crystals and single crystal fibers. A method of manufacturing improved phosphors and a method of manufacturing single crystal phosphors are also provided.

Claims

1. A phosphor represented by the formula:

space="preserve" listing-type="equation">MO . mAl.sub.2 O.sub.3 ;

Eu .sup.2++,R.sup.3+

wherein m is a number ranging from about 1.6 to about 2.2, M is Sr or a combination of Sr with Ca, Ba or both, R³⁺ is a trivalent metal ion or a mixture thereof, Eu²⁺ is present at a level from about 0.02 mol % to about 10 mol % of M, and R³⁺ is present at a level from about 0.02mol % to about 20 mol % of M.

2. The phosphor of claim 1 wherein R³⁺ is selected from the group Pr³⁺, Ho³⁺, Nd³⁺, Dy³⁺, Er³⁺, La³⁺, Lu³⁺, Ce³⁺, Y³⁺, Sm³⁺, Gd³⁺, Tb³⁺, Tm³⁺, Yb³⁺ and Bi³⁺.

3. The phosphor of claim 1 wherein R³⁺ is Pr³⁺, Ho³⁺, Dy³⁺, Nd³⁺ or mixtures thereof.

4. The phosphor of claim 1 which is a single crystal.

5. The phosphor of claim 1 which has the formula:

space="preserve" listing-type="equation">SrAl.sub.4 O.sub.7 ;

2xEu.sup.2+,2yR.sup.3+

wherein x can range from about 0.0001 to about 0.05, and y can range from about 0.0001 to about 0.10.

6. The phosphor of claim 5 wherein R³⁺, is Pr³⁺, Ho³⁺, a combination of Pr³⁺ with Dy³⁺, or a combination of Ho³⁺ with Dy³⁺.

7. The phosphor of claim 5 wherein x is a number ranging from about 0.0001 to about 0.005.

8. The phosphor of claim 1 wherein m is 2 or 1.75.

9. The phosphor of claim 8 wherein M is Sr.

10. A phosphor represented by the formula:

space="preserve" listing-type="equation">MO . mAl.sub.2 O.sub.3 ;

Eu.sup.2+,R.sup.3+

wherein m is a number ranging from about 1.6 to about 2.2, M is Sr or a combination of Sr with Ca, Ba or both, R³⁺ is a mixture of Y³⁺ with another trivalent metal ion, Eu²⁺ is present at a level from about 0.02 mol % to about 10 mol % of M, and R³⁺, is present at a level from about 0.02 mol % to about 20 mol % of M.

11. The phosphor of claim 10 wherein R³⁺ is a mixture of Y³⁺ with a trivalent metal ion selected from the group Pr³⁺, Ho³⁺, Nd³⁺, Dy³⁺, Er³⁺, La³⁺, Lu³⁺, Ce³⁺, Sm³⁺, Gd³⁺, Tb³⁺, Tm³⁺, Yb³⁺ and Bi³⁺.

12. A phosphor having the formula:

space="preserve" listing-type="equation">Sr.sub.k Ba.sub.p Ca.sub.n O . mAl.sub.2 O.sub.3 ;

2xEu.sup.2+,2yR.sup.3+

where k=1-n-p-2x-2y and k is greater than 0, and n and p are numbers greater than or equal to 0 and less than 1, x is a number that can range from about 0.0001 to about 0.05 and v is a number that can range from 0.0001 to about 0.10.

13. A method for making a single crystal phosphor which comprises the steps of:

(a) combining the phosphor components according to the stoichiometry of the formula;

space="preserve" listing-type="equation">MO . mAl.sub.2 O.sub.3 ;

Eu.sup.2+,R.sup.3+

wherein m is a number ranging from about 1.6 to about 2.2, M is Sr or a combination of Sr with Ca, Ba or both, R³⁺ is a trivalent metal ion or a mixture thereof, Eu²⁺ is present at a level from about 0.02mol % to about 10 mol % of M, and R³⁺ is present at a level from about 0.02 mol % to about 20 mol % of M to form a powder;

(b) sintering the powder in a reducing atmosphere;

(c) growing single crystals from the sintered powder under an inert atmosphere.

14. The method of claim 13 wherein a flux is combined with phosphor components in step (a).

15. A phosphor represented by the formula:

space="preserve" listing-type="equation">MO . mAl.sub.2 O.sub.3 ;

Eu.sup.2+,R.sup.3+

wherein m is a number ranging from about 1.6 to about 2.2, M is Sr or a combination of Sr with Ca, Ba or both, R³⁺ is a trivalent rare earth metal ion, Bi³⁺ or mixtures thereof, Eu²⁺ is present at a level from about 0.02 mol % to about 10 mol % of M, and R³⁺ is present at a level from about 0.02 mol % to about 20 mol % of M in which a portion of the Al³⁺ in the host is substituted by a divalent metal ion or in which a portion of the M² in the phosphor is substituted by a monovalent metal ion.

16. A phosphor of claim 15 wherein a portion of the Al³⁺ in the host is substituted by a divalent metal ion.

17. The phosphor of claim 16 wherein the divalent ion is Mg²⁺ or Zn²⁺ or a mixture thereof.

18. The phosphor of claim 16 in which M²⁺ in the phosphor is substituted by a monovalent metal ion.

19. The phosphor of claim 16 in which the amount of divalent metal ion substituted into the phosphor is equal to the amount of R³⁺ in the phosphor.

20. The phosphor of claim 16 in which the amount of divalent metal ion substituted into the phosphor ranges from about 0.02 mol % to about 20 mol %.

21. The phosphor of claim 15 in which a portion of the M²⁺ in the phosphor is substituted by a monovalent metal ion.

22. The phosphor of claim 21 in which the monovalent metal ion is Na⁺ or K⁺.

23. The phosphor of claim 22 in which the monovalent metal ion is present in the phosphor in an amount about equal to the amount of R³⁺ trivalent metal ion doped into the phosphor.

24. The phosphor of claim 21 in which the amount of divalent metal ion substituted into the phosphor ranges from about 0.02 mol % to about 20 mol %.

25. The phosphor of claim 15 wherein R³⁺ is selected from the group Pr³⁺, Ho³⁺, Nd³⁺, Dy³⁺, Er³⁺, La³⁺, Lu³⁺, Ce³⁺, Y³⁺, Sm³⁺, Gd³⁺, Tb³⁺, Tm³⁺, Yb³⁺ and Bi³⁺.

26. The phosphor of claim 15 wherein R³⁺ is Pr³⁺, Ho³⁺, Dy³⁺, or Nd³⁺ or mixtures thereof.

27. The phosphor of claim 15 wherein R³⁺ is a mixture of Y³⁺ with another trivalent metal ion.

28. The phosphor of claim 15 which is a single crystal.

29. The phosphor of claim 15 further comprising from about 2 mol % to about 20 mol % of B₂ O₃.

30. The phosphor of claim 15 wherein M is Sr.