Aluminate phosphor containing bivalence metal elements, its preparation and the light emitting devices incorporating the same

This application is a continuation application filed under 35 U.S.C. §111(a), claiming the benefit under 35 U.S.C. §120 and §365(c) of a PCT International Application Number PCT/CN2007/003205, filed Nov. 13, 2007, it being further noted that foreign priority benefit is based upon Chinese Patent Application 200610114519.8, filed Nov. 13, 2006 in the State Intellectual Property Office of P.R. China, the disclosures of which are thereby incorporated by reference.

This invention relates to an aluminate phosphor that can be excited by ultraviolet, purple or blue light, its preparation methods and the light emitting devices incorporating the same.

Solid state light sources (LEDs, light emitting diodes) have been paid much attention for many years. Since LEDs have many advantages, such as small volume, low power consumption, long lifetime, fast-response, environmental friendliness, high reliability, etc., they are widely used as components in decorating lamps, indicating lamps, etc. According to recent developments, it is possible for LEDs to be advanced into the general lighting field.

As for current LED technologies, white LEDs are recommended to generate by packaging blue LED and phosphors. In U.S. Pat. No. 5,998,925, Nichia achieved the white-light LED by combining (RE 1-r Sm r ) 3 (Al 1-s ,Ga s ) 5 O 12 yellow phosphor with GaInN blue-light LED. Then, Osram developed (Tb 1-x-y RE x Ce y ) 3 (Al,Ga) 5 O 12 phosphor for LEDs in U.S. Pat. No. 6,669,866. In 2002, General Research Institute for Nonferrous Metals and Grirem Advanced Materials Co., Ltd made public that the luminous intensity can be improved by coactivation mode in patent CN1482208 (general formula, R (3-x-y) M 5 O 12 :Ce x R′ y ). It is thought by the General Electric Company in U.S. Pat. No. 6,409,938 that the quantum efficiency and emission intensity of aluminate phosphor are far away from goals, and they could be improved when O 2− is partly substituted by F − .

However, our research results show that bivalent metal element can be introduced to improve the quantum efficiency and emission intensity. The bivalent metal element partly substitutes Al 3+ or Y 3+ of the phosphor, and can compensate for the charge center formed by F − substituting O 2− , which can promote the light conversion efficiency and improve the stability of this phosphor.

In this invention, the inventors present an aluminate phosphor by co-doped with bivalent metal element and fluorine. This phosphor has a broad excitation range, which can be excited by ultraviolet, purple or blue light, and exhibits high luminous efficiency and good stability. On the other hand, a light emitting device incorporating this phosphor is also concerned.

One aspect of the present invention is to provide a kind of phosphor that can be excited by ultraviolet, purple or blue light, and has excellent luminescent properties and stability.

Another aspect of the present invention is to provide a light emitting device which is incorporated above mentioned phosphor.

As one embodiment, the phosphor can be represented by the general formula

Ln a M b (O,F) 12 :(R 3+ ,M′ 2+ ) x , wherein

Ln is at least one metal element selected from a group consisting of Sc, Y, La, Pr, Nd, Gd, Ho, Yb and Sm, 2.6≦a≦3.4;

M is at least one metal element selected from a group consisting of B, Al and Ga, 4.5≦b≦5.5;

R is at least one metal element selected from a group consisting of Ce and Tb; and

M′ is at least one metal element selected from a group consisting of Ca, Sr, Ba, Mn and Zn, 0.001≦x≦0.4.

A preparation method necessary to produce the phosphor described above

according to the general formula Ln a M b (O,F) 12 :(R 3+ ,M′ 2+ ) x , wherein

Ln is at least one metal element selected from the group consisting of Sc, Y, La, Pr, Nd, Gd, Ho, Yb and Sm, 2.6≦a≦3.4;

M is at least one element selected from the group consisting of B, Al and Ga, 4.5≦b≦5.5; and

R is at least one metal element selected from the group consisting of Ce and Tb; M′ is at least one metal element selected from the group consisting of Ca, Sr, Ba, Mn and Zn, 0.001≦x≦0.4, includes the following:

1. selecting elementary substance or compounds (I) of Ln, M, R, M′ and fluoride (II) as raw materials, weighing the raw materials according to appropriate stoichiometric ratio, and adding the flux (III) into above raw materials, then mixing and grinding the raw materials together to form a mixture (IV),

2. baking the mixture (IV) at high temperature in reducing atmosphere to form a baked product, and

3. carrying out a post-treatment to the baked product to obtain the phosphor of the present invention.

According to step 1, compounds (I) of Ln, M, R and M′ are selected from the group of oxide, hydroxide, carbonate, nitrate and organic salt of Ln, M, R, M′, and fluoride (II) is at least one compound selected from fluorides of Ln, M, R, M′ and ammonium. Flux (III) is at least one compound selected from the group of alkali halide, alklide-earth halide, H 3 BO 3 , ammonium halide and compounds of Ln, M, R, M′.

According to 1 above, the amount of the flux is 0.01˜20% by weight of the mixture (IV).

According to 1 above, the starting materials could be mixed and grinded in alcohol, acetone or water.

According to 2 above, baking can be operated once, twice or more.

According to 2 above, the temperature of baking is in the range of 500˜1600° C.

According to 2 above, each baking should last for 0.5˜30 h.

According to 3 above, post-treatment involves grinding, air flow crushing, washing, drying and grading, etc.

According to 3 above, the washing in post-treatment uses acid solution, alkali solution or water.

According to 3 above, the grading step in post-treatment can be at least a method selected from sieving method, hydraulic classification and air flow grading.

It is easily found that the above synthetic method for producing the phosphor of the present invention is advantageous for being very simple, involving no pollution and having low cost. This phosphor can be excited by UV, purple or blue light, and then emits broadband visible light with wavelengths peaking at 500-600 nm and having full width at half maximum (FWHM) beyond 30 nm. That is to say, the phosphor in present invention can be satisfied with UV, purple or blue LED. Thus the present phosphor can be incorporated directly or along with other phosphors into LEDs to produce white or color light emitting devices.

In accordance with an aspect of the present invention, a light emitting device can be produced by combining the phosphor of the present invention with at least one kind of LED, such as UV, purple or blue LED. The phosphor can be expressed by general formula:

Ln a M b (O,F) 12 :(R 3+ ,M′ 2+ ) x , wherein

Ln is at least one metal element selected from a group consisting of Sc, Y, La, Pr, Nd, Gd, Ho, Yb and Sm, 2.6≦a≦3.4;

M is at least one metal element selected from a group consisting of B, Al and Ga, 4.5≦b≦5.5;

R is at least one metal element selected from a group consisting of Ce and Tb; and

M′ is at least one metal element selected from a group consisting of Ca, Sr, Ba, Mn and Zn, 0.001≦x≦0.4.

In the above-mentioned light emitting devices, other phosphors can be introduced.

1 The above-described phosphors of the present invention have novel composition and excellent luminescent properties and stability.

The preparation methods for producing the phosphors are simple, involving no pollution and having lower cost.

New light emitting devices can be obtained by incorporating the phosphor into LED, which have long lifetime and high luminous efficiency.

FIG. 1 shows the excitation spectrum of Example 1;

FIG. 2 shows the emission spectra of the samples of Examples 1, and 2 and Comparative Examples 1-3.

Raw materials Y 2 O 3 (4N), BaCO 3 (4N), Al 2 O 3 (4N), CeO 2 (4N) and NH 4 F (AR) are weighed with appropriate stoichiometric ratio. NH 4 F (AR) acts as both reactant and flux. Preparation of this Phosphor is Carried Out with Mixing and Grinding of these Materials, and baking at 1450° C. for 3 hours in reducing atmosphere. After that, the phosphor Y 2.75 Al 5 O 11.8 F 0.2 :(Ce 0.05 ,Ba 0.2 ) can be obtained by crushing, washing, drying and sieving sequentially. The excitation spectrum and emission spectrum are shown in FIG. 1 , it can be seen that the phosphor can be excited by UV, purple and blue light and emits 541 nm yellow light.

Comparative Example 1

Raw materials Y 2 O 3 (4N), Al 2 O 3 (4N), CeO 2 (4N) and AlF 3 (4N) are weighed with appropriate stoichiometric ratio. AlF 3 (4N) acts as both reactant and flux. Preparation of the Phosphor is Carried Out with Mixing and Grinding of these Materials, and baking at 1450° C. for 3 hours in reducing atmosphere. After that, the phosphor Y 2.95 Al 5 O 11.8 F 0.2 :Ce 0.05 can be obtained by crushing, washing, drying and sieving sequentially.

Comparative Example 2

Raw materials Y 2 O 3 (4N), Al 2 O 3 (4N), CeO 2 (4N) and YF 3 (4N) are weighed with appropriate stoichiometric ratio. YF 3 (4N) acts as both reactant and flux. Preparation of the phosphor is carried out with mixing and grinding of these materials, and baking at 1450° C. for 3 hours in reducing atmosphere. After that, the phosphor Y 2.95 Al 5 O 11.8 F 0.2 :Ce 0.05 can be obtained by crushing, washing, drying and sieving sequentially.

Comparative Example 3

Raw materials Y 2 O 3 (4N), Al 2 O 3 (4N), CeO 2 (4N) and H 3 BO 3 (AR) are weighed with appropriate stoichiometric ratio. H 3 BO 3 (AR) acts as flux. Preparation of the phosphor is carried out with mixing and grinding of these materials, and baking at 1450° C. for 3 hours in reducing atmosphere. After that, the phosphor Y 2.95 Al 5 O 12 :CeO 0.05 can be obtained by crushing, washing, drying and sieving sequentially.

The main emission peak wavelength and relative intensity of the phosphors of the above examples are shown in Table 1. It can be found that bivalence metal element improves the emission intensity of the phosphor greatly.

Examples 2-11

Each sample is synthesized according to the corresponding formula as shown in Table 2 respectively. Hosts, activators and fluxes are changed in those embodiments. Synthetic method is the same as Example 1. The main emission peak wavelength and relative intensity of the phosphors for these embodiments are shown in Table 2.

White light emitting device can be obtained by incorporating the phosphor of Example 1 into a GaInN blue light LED. The powder of the phosphor is firstly dispersed in resin, and then coated on a GaInN LED chip. After welding circuit and packaging, a white light emitting device is produced.

The above-described phosphor is readily produced and shows high emission intensity in light emitting device, and a light emitting device using the phosphor are provided.