NOVEL SILICATE-BASED YELLOW-GREEN PHOSPHORS

• US 20080116786A1
• Filed: 12/24/2007
• Published: 05/22/2008
• Est. Priority Date: 08/04/2004
• Status: Active Grant

• Current Assignee: Intematix Corporation
• Original Assignee: Intematix Corporation
• Inventors: Dong, Yi, Cheng, Shifan, Li, Yi-Qun, Wang, Ning
• Granted Patent: US 8,017,035 B2
• Time in Patent Office: Days
• US Class Current: 313/503
• CPC Class Codes: C09K 11/0883 Arsenides; Nitrides; Phosphides
• CPC Class Codes: C09K 11/77348 Silicon Aluminium Nitrides or Silicon Aluminium Oxynitrides
• CPC Class Codes: H01L 33/502 Wavelength conversion materials
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps

Abstract

Novel phosphor systems are disclosed having the formula A₂SiO₄:Eu²⁺D, where A is at least one of a divalent metal selected from the group consisting of Sr, Ca, Ba, Mg, Zn, and Cd; and D is a dopant selected from the group consisting of F, Cl, Br, I, P, S, N, and B. In one embodiment, the novel phosphor has the formula (Sr_1−x−yBa_xM_y)₂SiO₄:Eu²⁺F (where M is one of Ca, Mg, Zn, or Cd in an amount ranging from 0<y<0.5). The phosphor is configured to absorb visible light from a blue LED, and luminescent light from the phosphor plus light from the blue LED may be combined to form white light. The novel phosphors can emit light at intensities greater than either conventionally known YAG compounds, or silicate-based phosphors that do not contain the inventive dopant ion.

Claims

1. A silicate-based yellow-green phosphor having the formula A₂SiO₄:

Eu²⁺D, wherein;

A is at least one of a divalent metal selected from the group consisting of Sr, Ca, Ba, Mg, Zn, and Cd; and

D is a dopant selected from the group consisting of F, Cl, Br, I, P, S, N, and B, wherein D is present in the phosphor in an amount ranging from about 0.01 to 20 mole percent, and wherein at least some of the D dopant substitutes for oxygen anions to become incorporated into the crystal lattice of the silicate-based yellow-green phosphor.

2. The silicate-based phosphor of claim 1, wherein the phosphor is configured to absorb radiation in a wavelength ranging from about 280 nm to 490 nm.

3. The silicate-based phosphor of claim 1, wherein the phosphor emits visible light having a wavelength ranging from about 460 nm to 590 mm.

4. The silicate-based phosphor of claim 1, wherein the phosphor has the formula (Sr₁₋

x−

yBa_xM_y)₂SiO₄;

Eu²⁺D, where M is at least one of an element selected from the group consisting of Ca, Mg, Zn, and Cd, and where

0≦

x≦

1;

0≦

y≦

1 when M is Ca;

0≦

y≦

1 when M is Mg; and

0≦

y≦

1 when M is selected from the group consisting of Zn and Cd.

5. The silicate-based phosphor of claim 1, wherein D is selected from the group consisting of N, B, Cl, and S.

6. The silicate-based phosphor of claim 1, wherein the phosphor has the formula (Sr₁₋

x−

yBa_xM_y)₂SiO₄;

Eu²⁺Cl, S, N, B, where M is at least one of an element selected from the group consisting of Ca, Mg, Zn, Cd, and where

0≦

x≦

0.3;

0≦

y≦

0.5 when M is Ca;

0≦

y≦

0.1 when M is Mg; and

0≦

y≦

0.5 when M is selected from the group consisting of Zn and Cd.

7. The silicate-based phosphor of claim 6, wherein the phosphor emits light in the yellow region of the electromagnetic spectrum, and has a peak emission wavelength ranging from about 540 to 590 nm.

8. The silicate-based phosphor of claim 1, wherein the phosphor has the formula (Sr₁₋

x−

yBa_xM_y)₂SiO₄;

Eu²⁺Cl, S, N, B, where M is at least one of an element selected from the group consisting of Ca, Mg, Zn, and Cd, and where

0.3≦

x≦

1;

0≦

y≦

0.5 when M is Ca;

0≦

y≦

0.1 when M is Mg; and

0≦

y≦

0.5 when M is selected from the group consisting of Zn and Cd.

9. The silicate-based phosphor of claim 8, wherein the phosphor emits light in the green region of the electromagnetic spectrum, and has a peak emission wavelength ranging from about 500 to 540 nm.

10. A white LED comprising:

a radiation source configured to emit radiation having a wavelength ranging from about 410 to 500 nm;

a yellow phosphor according to claim 7, the yellow phosphor configured to absorb at least a portion of the radiation from the radiation source and emit light with a peak intensity in a wavelength ranging from about 540 to 590 nm.

11. A white LED comprising:

a radiation source configured to emit radiation having a wavelength ranging from about 410 to 500 nm;

a yellow phosphor according to claim 7, the yellow phosphor configured to absorb at least a portion of the radiation from the radiation source and emit light with peak intensity in a wavelength ranging from about 540 to 590 nm; and

a green phosphor configured to absorb at least a portion of the radiation from the radiation source and emit light with peak intensity in a wavelength ranging from about 500 to 540 nm.

12. A white LED comprising:

a radiation source configured to emit radiation having a wavelength ranging from about 410 to 500 nm;

a green phosphor according to claim 9, the green phosphor configured to absorb at least a portion of the radiation from the radiation source and emit light with peak intensity in a wavelength ranging from about 500 to 540 nm; and

a red phosphor selected from the group consisting of

CaS;

Eu²⁺;

SrS;

Eu²⁺;

MgO*MgF*GeO;

Mn⁴⁺;

a nitridosilicate, an aluminonitridosilicate, an oxynitridosilicate, and an oxynitridoaluminosilicate;

M_xSi_yN_z;

Eu²⁺ where M is selected from the group consisting of Ca, Sr, Ba, and Zn; and

Z=⅔

x+ 4/3y;

M₂Si₅N₈;

Eu²⁺, where M is Ca, Sr, and Ba;

CaSiN₂;

Eu²⁺;

CaAlSiN₃;

Eu²⁺;

(Ca<sub>1−

x−

y−

z</sub>Sr_xBa_yMg_z)<sub>1−

n</sub>(Al<sub>1−

a+b</sub>B_a)Si<sub>1−

b</sub>N<sub>3−

b</sub>O_b;

RE_n, where 0≦

x≦

1, 0≦

y≦

1, 0≦

z≦

1, 0≦

a≦

1, 0<

b≦

1, 0.002≦

n≦

0.2, and RE is selected from the group consisting of Eu²⁺ and Ce³⁺; and

wherein the red phosphor is configured to absorb at least a portion of the radiation from the radiation source and emit light with peak intensity in a wavelength ranging from about 590 to 690 nm.

13. A white LED comprising:

a radiation source configured to emit radiation having a wavelength ranging from about 410 to 500 nm;

a yellow phosphor according to claim 7, the yellow phosphor configured to absorb at least a portion of the radiation from the radiation source and emit light with a peak intensity in a wavelength ranging from about 540 to 590 nm; and

a red phosphor selected from the group consisting of

CaS;

Eu²⁺;

SrS;

Eu²⁺;

MgO*MgF*GeO;

Mn⁴⁺;

a nitridosilicate, an aluminonitridosilicate, an oxynitridosilicate, and an oxynitridoaluminosilicate;

M_xSi_yN_z;

Eu²⁺ where M is selected from the group consisting of Ca, Sr, Ba, and Zn; and

Z=⅔

x+ 4/3y;

M₂Si₅N₈;

Eu²⁺, where M is Ca, Sr, and Ba;

CaSiN₂;

Eu²⁺;

CaAlSiN₃;

Eu²⁺;

(Ca<sub>1−

x−

y−

z</sub>Sr_xBa_yMg_z)<sub>1−

n</sub>(Al<sub>1−

a+b</sub>B_a)Si<sub>1−

b</sub>N<sub>3−

b</sub>O_b;

RE_n where 0≦

x≦

1, 0≦

y≦

1, 0≦

z≦

1, 0≦

a≦

1, 0<

b≦

1, 0.002≦

n≦

0.2, and RE is selected from the group consisting of Eu²⁺ and Ce³⁺; and

wherein the red phosphor is configured to absorb at least a portion of the radiation from the radiation source and emit light with peak intensity in a wavelength ranging from about 590 to 690 nm.

14. A composition comprising:

a silicate-based yellow phosphor having the formula A₂SiO₄;

Eu²⁺D, wherein A is at least one divalent metal selected from the group consisting of Sr, Ca, Ba, Mg, Zn, and Cd; and

D is a negatively charged halogen ion that is present in the yellow phosphor in an amount ranging from about 0.01 to 20 mole percent;

wherein at least some of the negatively charged halogen ions D substitute for oxygen anions to become incorporated into the crystal lattice of the silicate-based yellow phosphor; and

a blue phosphor;

wherein the yellow phosphor is configured to emit visible light with a peak intensity in a wavelength ranging from about 540 nm to 590 nm; and

the blue phosphor is configured to emit visible light with a peak intensity in a wavelength ranging from about 430 to 510 nm.

15. The composition of claim 14, wherein the blue phosphor is selected from the group consisting of silicate-based phosphors and aluminate-based phosphors.

16. The composition of claim 15, wherein the silicate-based blue phosphor has the formula Sr₁₋

x−

yMg_xBa_ySiO₄;

Eu²⁺F; and

where

0.5≦

x≦

1.0; and

0≦

y≦

0.5.

17. The composition of claim 15, wherein the aluminate-based blue phosphor has the formula Sr₁₋

xMgEu_xAl₁₀O₁₇; and

where 0.01<

x≦

1.0.

18. A composition comprising:

a silicate-based green phosphor having the formula A₂SiO₄;

Eu²⁺D, wherein A is at least one of a divalent metal selected from the group consisting of Sr, Ca, Ba, Mg, Zn, and Cd; and

D is a negatively charged halogen ion that is present in the green phosphor in an amount ranging from about 0.01 to 20 mole percent, wherein at least some of the negatively charged halogen ion D substitutes for oxygen anions and thus are incorporated into the crystal lattice of the silicate-based green phosphor;

a blue phosphor; and

a red phosphor;

wherein the green phosphor is configured to emit visible light with a peak intensity in a wavelength ranging from about 500 nm to 540 nm;

the blue phosphor is configured to emit visible light with a peak intensity in a wavelength ranging from about 430 to 510 nm; and

the red phosphor is configured to emit visible light with a peak intensity in a wavelength ranging from about 575 to 690 nm.

19. A method of preparing a silicate-based yellow phosphor having the formula A₂SiO₄:

Eu²⁺D, wherein A is at least one of a divalent metal selected from the group consisting of Sr, Ca, Ba, Mg, Zn, and Cd; and

D is a dopant selected from the group consisting of F, Cl, Br, I, B, S, and N, wherein D is present in the phosphor in an amount ranging from about 0.01 to 20 mole percent, the method using a wet mixing step to incorporate at least some of the D dopant into the crystal lattice of the silicate-based yellow phosphor.

20. The method of claim 19, wherein the method comprises:

a) dissolving a desired amount of an alkaline earth nitrate selected from the group consisting of Mg, Ca, Sr, and Ba-containing nitrates with Eu₂O₃ and a compound selected from the group consisting of BaF₂, NH₄F, an alkaline earth metal halide and an ammonium halide, in an acid, to prepare a first solution;

b) dissolving a corresponding amount of a silica gel in de-ionized water to prepare a second solution;

c) stirring together the solutions produced in steps a) and b), and then adding ammonia to generate a gel from the mixture solution;

d) adjusting the pH of the solution produced in step c) to a value of about 9, and then stirring the solution continuously at about 60°

C. for about 3 hours;

e) drying the gelled solution of step d) by evaporation, and then decomposing the resulting dried gel at 500 to 700°

C. for about 60 minutes to decompose and acquire product oxides;

f) cooling and grinding the dried gel of step e) to produce a powder;

g) calcining/sintering the powder of step f) in a reduced atmosphere for about 6 to 10 hours, the sintering temperature ranging from about 1200 to 1400°

C.

21. The method of claim 19, wherein the method comprises:

a) wet mixing desired amounts of an alkaline earth oxide or carbonate, the alkaline earth selected from the group consisting of Mg, Ca, Sr, and Ba, Eu₂O₃, and a dopant selected from the group consisting of BaF₂, NH₄F, an alkaline earth metal halide, and an ammonium halide, and corresponding amounts of SiO;

b) after drying and grinding, calcining and/or sintering the resulting powder in a reduced atmosphere for about 6 to 10 hours at a calcining/sintering temperature ranging from about 1200 to 1400°

C.