U.S. patent application number 12/453681 was filed with the patent office on 2009-09-17 for light phosphor with zeolitic structure.
This patent application is currently assigned to National Tsing Hua University. Invention is credited to Yueh-Chun Liao, Chia-Her Lin, Sue-Lein Wang.
Application Number | 20090230358 12/453681 |
Document ID | / |
Family ID | 38002840 |
Filed Date | 2009-09-17 |
United States Patent
Application |
20090230358 |
Kind Code |
A1 |
Wang; Sue-Lein ; et
al. |
September 17, 2009 |
Light phosphor with zeolitic structure
Abstract
The present invention is related to a phosphor that can be
excited by UV light between 375 to 400 nm to emit white light,
which is intrinsically produced by emitting blue light with yellow
light simultaneously. This compound is synthesized from organic
amine, metal oxide and phosphate under hydrothermal conditions, and
gives rise to a zeolitic structure with the chemical formula of
(A).sub.5-x/2[Zn.sub.9-xGa.sub.xO(HPO.sub.4)(PO.sub.4).sub.8].yH.sub.2O
(0<x<9, 0<y<15). On the other hand, when synthesized by
different solvents, it is possible to obtain a phosphor of the same
chemical formula and structure, but it can emit yellow light when
excited by UV light or blue light emitted by LED between 300 to 500
nm.
Inventors: |
Wang; Sue-Lein; (Hsinchu,
TW) ; Liao; Yueh-Chun; (Hsinchu, TW) ; Lin;
Chia-Her; (Hsinchu, TW) |
Correspondence
Address: |
BACON & THOMAS, PLLC
625 SLATERS LANE, FOURTH FLOOR
ALEXANDRIA
VA
22314-1176
US
|
Assignee: |
National Tsing Hua
University
Hsinchu
TW
|
Family ID: |
38002840 |
Appl. No.: |
12/453681 |
Filed: |
May 19, 2009 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11454944 |
Jun 19, 2006 |
|
|
|
12453681 |
|
|
|
|
Current U.S.
Class: |
252/301.16 |
Current CPC
Class: |
C09K 11/625 20130101;
C09K 11/703 20130101; Y02B 20/181 20130101; Y02B 20/00
20130101 |
Class at
Publication: |
252/301.16 |
International
Class: |
C09K 11/06 20060101
C09K011/06 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 7, 2005 |
TW |
94139015 |
Claims
1-12. (canceled)
13. A method for preparing a phosphor having a chemical formula as
follows:
(A).sub.5-x/2[M.sub.9-xGa.sub.xO(HPO.sub.4)(PO.sub.4).sub.8].yH-
.sub.2O wherein 0<x<9; 0<y<15, M is a transition metal,
and A is a cation of Group 1A metal or a protonated organic amine,
said method comprising the following steps: preparing a mixed
solution comprising a gallium source, a source of M, phosphate, a
template, and water, and optionally an alcohol; and heating the
mixed solution to carry out a hydrothermal reaction, wherein the
gallium source comprises a gallium metal, a gallium salt, or a
gallium oxides, and the M source comprises a M metal, a M metal
salt, or a M metal oxide.
14. The method of claim 13, wherein the template comprises an
organic amine.
15. The method of claim 14, wherein the organic amine is
4,4'-trimethylenedipyridine.
16. The methods of claim 13, wherein M is a transition metal of
Group 2B.
17. The method of claim 15, wherein M is Zn.
18. The method of claim 16, wherein the alcohol is ethylene glycol
or n-butanol.
19. The method of claim 17, wherein x is 6; y is 5.
20. The method of claim 19, wherein the mole ratio of
4,4'-trimethylenedipyridine:Zn:Ga:H.sub.3PO.sub.4 in the mixed
solution equals to 6.4:1:1:6.
21. The method of claim 20, wherein the mixed solution does not
comprise the alcohol.
22. The method of claim 20, wherein the mixed solution comprises
the alcohol.
23. The method of claim 21, wherein when the phosphor is excited by
a light from UV light to blue light with a wavelength between 270
to 500 nm, it emits yellow light with a wavelength between 520 to
620 nm.
24. The method of claim 22, wherein when the phosphor is excited by
a light source with a wavelength between 270 to 420 nm, it emits
blue light with a wavelength between 400 to 500 nm; when it is
excited by a light source with a wavelength between 280 to 500 nm,
it emits yellow light with a wavelength between 520-650; when it is
excited by a light source with a wavelength between 280 to 420, it
emits white light that is produced by mixing blue light and yellow
light.
25. The method of claim 19 further comprising contacting the
resulting phosphor from the hydrothermal reaction with a solution
containing cations of Group 1A metal, so that the protonated
4,4'-trimethylenedipyridine and the cations of Group 1A metal are
cation exchanged.
26. The method of claim 16, wherein the hydrothermal reaction is
carried out at 160 to 180.degree. C. for a period of 1 to 10
days.
27. The method of claim 26, wherein the hydrothermal reaction is
carried out for a period of 3 to 7 days.
28. The method of claim 13, wherein the hydrothermal reaction is
carried out in the mixed solution having a pH value of 3.5 to
6.5.
29. The method of claim 28, wherein the pH value is 5.0.
30. The method of claim 13, wherein the mixed solution further
comprises a diacid.
31. The method of claim 30, wherein the diacid is oxalic acid.
Description
FIELD OF THE INVENTION
[0001] The present invention is related to a phosphor with a
zeolitic structure of a transition metal gallophosphate, and more
particularly, the present invention is related to a phosphor that
can emit yellow light, or can emit blue light, yellow light, or
white light that is the mixture of blue light and yellow light.
BACKGROUND OF THE INVENTION
[0002] The main purpose of white LED in the future is thought to be
the substitution for the traditional lighting, especially lighting
equipment such as tungsten bulbs or fluorescent lights. This is
because LED has more advantages than the traditional lighting; such
as its small size, low heat emission, low energy consumption,
longer longevity, shorter response time, and zero mercury
pollution. Therefore, in addition to being employed in traditional
lighting in the future, LED also has wide applications in various
industries, such as being used as the indicator and internal
lighting of cars, dashboard, as well as LCD backlight panel.
[0003] There are currently two major techniques for producing white
LED globally; the first one is mainly employed in commerce right
now, which produces white light by using a blue light emitting
diode to excite yellow phosphor powder. However, the phosphor
powder required by this technique is owned by companies in Japan
and the U.S. For example, a yellow phosphor powder that is
abbreviated as YAG, and with the composition of (Y,
Ce).sub.3Al.sub.5O.sub.12, was developed by Nichia Corporation of
Japan. On the other hand, a second technique that is still being
developed now produces white light by using the UV-LED of the
wavelength less than 400 nm to excite phosphor powders with three
different RGB colors. Because more than one phosphor powders are
required by this technique, it is not only necessary to find the
phosphor powders that can complement one another, whether the
deterioration rates of various phosphor powders are uniform must
also be considered, which is an important factor that affects the
quality of the resultant white light. Therefore, it can be
concluded from above that phosphor powder will play a crucial role
in the development of white LED, no matter in the current white LED
techniques or the ones in the coming future.
[0004] The luminescence properties of a phosphor powder is related
to its chemical composition, a phosphor powder of the same chemical
composition and structure but with different luminescence
properties has not yet be developed so far.
SUMMARY OF THE INVENTION
[0005] A primary objective of the present invention is to provide a
novel phosphor, which has a zeolitic structure.
[0006] Another objective of the present invention is to provide a
novel phosphor with zeolitic structure that can intrinsically emit
yellow light, blue light, or white light that is produced by mixing
blue light and yellow light.
[0007] Another objective of the present invention is to provide a
method for emitting light, comprising exciting the phosphor of the
present invention by a light from UV light to blue light having a
wavelength between 270 to 500 nm, to emit yellow light, blue light,
or white light that is produced by mixing blue light and yellow
light.
[0008] A further objective of the present invention is to provide a
method for preparing a novel phosphor with zeolitic structure.
[0009] In order to accomplish the above-mentioned objectives, a
phosphor synthesized according to the present invention has a
zeolitic structure and has a chemical formula as follows:
(A).sub.5-x/2[M.sub.9-xGa.sub.xO(HPO.sub.4)(PO.sub.4).sub.8].yH.sub.2O
wherein 0<x<9; 0<y<15, M is a transition metal, and A
is a cation of Group 1A metal or a protonated organic amine.
Preferably, the organic amine is 4,4'-trimethylenedipyridine, and
the Group 1A metal is lithium, sodium, or potassium.
[0010] Preferably, M is a transition metal of Group 2B. More
preferably, M is Zn.
[0011] Preferably, x is 6; y is 5.
[0012] The present invention also discloses a method of emitting
light comprising exciting a phosphor powder as defined in claim 1
by using a light from UV light to blue light of the wavelength
ranging from 270 to 500 nm.
[0013] The present invention further discloses a method for
preparing a phosphor having a chemical formula as follows:
(A).sub.5-x/2[M.sub.9-xGa.sub.xO(HPO.sub.4)(PO.sub.4).sub.8].yH.sub.2O
wherein 0<x<9; 0<y<15, M is a transition metal, and A
is a cation of Group 1A metal or a protonated organic amine, said
method comprising the following steps:
[0014] preparing a mixed solution comprising a gallium source, a
source of M, phosphate, a template, and water, and optionally an
alcohol; and
[0015] heating the mixed solution to carry out a hydrothermal
reaction, wherein the gallium source comprises a gallium metal, a
gallium salt, or a gallium oxides, and the M source comprises a M
metal, a M metal salt, or a M metal oxide.
[0016] Preferably, the template comprises an organic amine, and
more preferably, the organic amine is
4,4'-trimethylenedipyridine.
[0017] Preferably, M is a transition metal of Group 2B. More
preferably, M is Zn.
[0018] Preferably, the alcohol is ethylene glycol or n-butanol.
[0019] Preferably, x is 6; y is 5.
[0020] Preferably, the mole ratio of
4,4'-trimethylenedipyridine:Zn:Ga:H.sub.3PO.sub.4 in the mixed
solution equals to 6.4:1:1:6.
[0021] Preferably, the mixed solution does not comprise the
alcohol. In this case, the phosphor so prepared emits yellow light
with a wavelength between 520 to 620 nm, when the phosphor is
excited by a light from UV light to blue light with a wavelength
between 270 to 500 nm.
[0022] Preferably, wherein the mixed solution comprises the
alcohol. In this case, the phosphor so prepared emits blue light
with a wavelength between 400 to 500 nm, when the phosphor is
excited by a light source with a wavelength between 270 to 420 nm;
it emits yellow light with a wavelength between 520-650, when it is
excited by a light source with a wavelength between 280 to 500 nm;
it emits white light that is produced by mixing blue light and
yellow light when it is excited by a light source with a wavelength
between 280 to 420.
[0023] Preferably, the method for preparing a phosphor of the
present invention further comprises contacting the resulting
phosphor from the hydrothermal reaction with a solution containing
cations of Group 1A metal, so that the protonated
4,4'-trimethylenedipyridine and the cations of Group 1A metal are
cation exchanged.
[0024] Preferably, the hydrothermal reaction is carried out at 160
to 180.degree. C. for a period of 1 to 10 days, and more
preferably, for a period of 3 to 7 days.
[0025] Preferably, the hydrothermal reaction is carried out in the
mixed solution having a pH value of 3.5 to 6.5, and more
preferably, a pH value of 5.0.
[0026] Preferably, the mixed solution further comprises a diacid,
and more preferably, the diacid is oxalic acid.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 is a schematic view showing the zeolitic structure of
the phosphor having the formula (I) of the present invention.
[0028] FIG. 2 is a powder X-ray diffraction pattern of the phosphor
I-Y prepared by using water as the solvent in EXAMPLE 1 of the
present invention.
[0029] FIG. 3 is a powder X-ray diffraction pattern of the
phosphor-I-W prepared by using a mixed solvent of water and
ethylene glycol as the solvent in EXAMPLE 2 of the present
invention.
[0030] FIG. 4 is an emission spectrum of the phosphor I-Y prepared
in EXAMPLE 1 of the present invention, which is excited by
utilizing blue LED of 494 nm.
[0031] FIG. 5 is an excitation spectrum of the phosphor I-Y
prepared in EXAMPLE 1 of the present invention.
[0032] FIG. 6 is an emission spectrum of the phosphor I-W powder
prepared in EXAMPLE 2 the present invention, which is excited by
utilizing UV light of 384 nm.
[0033] FIG. 7 is the excitation spectrum of phosphor I-W prepared
in EXAMPLE 2 of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0034] A novel phosphor with zeolitic structure synthesized in one
of the preferred embodiments of the present invention has a
chemical composition described as below:
(A).sub.5-x/2[Zn.sub.9-xGa.sub.xO(HPO.sub.4)(PO.sub.4).sub.8].yH.sub.2O
(I)
wherein 0<x<9, 0<y<15, and A is a
NH.sub.4.sup.+-containing cation or cation of Group 1A metal. As
shown in FIG. 1, a zeolitic structure build up with unique
tetrahedral of two GaO.sub.4 and three ZnO.sub.4/GAO.sub.4
corner-shared with HPO.sub.4 or PO.sub.4 to generate a
three-dimensional network. The cation of A in the formula (I) and
water molecule reside in the channel intersections in the zeolitic
structure.
[0035] A suitable method for preparing the phosphor of formula (I)
is the hydrothermal technique, comprising the following steps:
[0036] (a) Organic amine, zinc source, and gallium source are
dissolved or dispersed in aqueous phosphate solution, which is then
placed in a reactor. [0037] (b) A solvent is added into the reactor
until the content in the reactor reaches 60% of the height of the
reactor, and the resulting mixture is stirred thoroughly, and the
pH value thereof is controlled at 5.0. [0038] (c) The synthesis
reaction is carried out under hydrothermal condition at a constant
temperature of 160.degree. C. for 1 to 10 days; the resultant
product is a phosphor powder with zeolitic structure and has the
chemical formula of (I). The yield is approximately 90%.
[0039] Preferably, the reactants in step (a) are
4,4'-trimethylenedipyridine (abbreviated as tmdp); zinc chloride
(ZnCl.sub.2), gallium oxide (Ga.sub.2O.sub.3), and aqueous
phosphate solution (85% H.sub.3PO.sub.4). More preferably, the mole
ratio between tmdp:ZnCl.sub.2:Ga.sub.2O.sub.3:H.sub.3PO.sub.4 are
6.4:1:0.5:6. The constant temperature for reaction in step (c) is
preferably maintained for 3 to 7 days.
[0040] The type of solvent utilized in step (b) will directly
affect the luminescence properties of the resultant product. In one
of the preferred embodiments of the present invention, where pure
water was used as the solvent, the resultant product emitted yellow
light with a wavelength of 550 nm when it was excited by UV light
or blue LED. On the other hand, when the solvent used contained an
organic solvent in addition to water, the resultant product emitted
blue-purple light with a wavelength of 430 nm and yellow light with
a wavelength of 550 nm when it was excited by UV light of 384 nm.
These two emitted lights would then mix and generate a white light.
Said organic solvent is a solvent having an OH radical, such as
alcohols, and preferably is ethylene glycol or n-butanol. When the
solvent used in step (b) contained an organic solvent having an OH
radical, the amount of said organic solvent to pure water is 1:1 in
volume to.
[0041] In the present invention, the cation A in the formula
(A).sub.5-x/2[Zn.sub.9-xGa.sub.xO(HPO.sub.4)(PO.sub.4).sub.8].yH.sub.2O
is ion exchangeable, for example some or substantially all the
organic amine cations (A in the formula) can be replaced by alkali
metal ions by carrying out ion exchange in an aqueous solution
containing metal ions of Group 1A at 80.degree. C. Accordingly, A
can be protonated tmdp (organic amine) or cation of Group 1A metal,
but the luminescence properties thereof are the same.
[0042] The present invention can be better understood from the
following examples which are merely for elucidation, not for
restricting the scope of the present invention.
Example 1
Phosphor I-Y
[0043] 1.267 g of tmdp, 0.136 g of zinc chloride (ZnCl.sub.2),
0.094 g of gallium oxide (Ga.sub.2O.sub.3), and 0.405 ml of aqueous
phosphate solution (85% H.sub.3PO.sub.4) were mixed together (the
mole ratio between
tmdp:ZnCl.sub.2:Ga.sub.2O.sub.3:H.sub.3PO.sub.4:=6.4:1:0.5:6). The
resulting aqueous solution was placed in a reactor, and then 12 ml
of deionized water was added into the reactor. The content in the
reactor was stirred thoroughly and an inorganic acid was added in
order to control the pH value of the solution at 5.0. A
hydrothermal reaction was carried out in the reactor at a constant
temperature of 160.degree. C. for 7 days, and a crystalline product
of phosphor (I-Y) was obtained. Yield: approximately 90%.
[0044] A yellow plate-shaped crystal of adequate size was selected
to carry out single-crystal X-ray diffraction analysis, from which
its chemical formula is known to be
(H.sub.2tmdp).sub.2[Zn.sub.3Ga.sub.6O(HPO.sub.4)(PO.sub.4).sub.8].5H.sub.-
2O. Electron probe X-ray micro-analysis (EPMA) further proved that
the atom ratio between Zn and Ga is 1:2. In addition, the following
element analysis also proved that the organic contents in the
formula.
Element Analysis:
TABLE-US-00001 [0045] N % C % H % Calculated Found Calculated Found
Calculated Found I-Y 2.83 2.76 15.78 15.52 2.29 2.29
Example 2
Phosphor I-W
[0046] 1.267 g of tmdp, 0.136 g of zinc chloride (ZnCl.sub.2),
0.094 g of gallium oxide (Ga.sub.2O.sub.3), and 0.405 ml of aqueous
phosphate solution (85% H.sub.3PO.sub.4) were mixed together (the
mole ratio between
tmdp:ZnCl.sub.2:Ga.sub.2O.sub.3:H.sub.3PO.sub.4:=6.4:1:0.5:6). The
resulting aqueous solution was placed in a reactor, and then a
mixed solvent of 6 ml of deionized water and 6 ml of ethylene
glycol was added into the reactor. The content in the reactor was
stirred thoroughly and an inorganic acid was added in order to
control the pH value of the solution at 5.0. A hydrothermal
reaction was carried out in the reactor at a constant temperature
of 160.degree. C. for 7 days, and a crystalline product of phosphor
(I-W) was obtained. Yield: approximately 90%.
[0047] A yellow plate-shaped crystal of adequate size was selected
to carry out single-crystal X-ray diffraction analysis, from which
its chemical formula is known to be
(H.sub.2tmdp).sub.2[Zn.sub.3Ga.sub.6O(HPO.sub.4)(PO.sub.4).sub.8].5H.sub.-
2O. EPMA data further proved that the atom ratio between Zn and Ga
is 1:2. In addition, the following element analysis also proved
that the organic contents in the formula.
Element Analysis:
TABLE-US-00002 [0048] N % C % H % Calculated Found Calculated Found
Calculated Found I-W 2.83 2.76 15.78 15.52 2.29 2.29
[0049] The solvent used in EXAMPLE 1 is pure water, and the
resultant product is a yellow powder I-Y with the chemical formula
of
(H.sub.2tmdp).sub.2[Zn.sub.3Ga.sub.6O(HPO.sub.4)(PO.sub.4).sub.8].5H.sub.-
2O. Its luminescence properties are shown is FIG. 4. When the
powder is excited by UV or blue light, it emits yellow light with a
wavelength of 550 nm.
[0050] The solvent used in EXAMPLE 2 is a mixed solvent containing
water and ethylene glycol (the volume ratio was 1:1), and the
resultant product I-W is a brown powder that also has the chemical
formula of
(H.sub.2tmdp).sub.2[Zn.sub.3Ga.sub.6O(HPO.sub.4)(PO.sub.4).sub.8].5H.sub.-
2O. Its luminescence properties are shown is FIG. 6. When the
powder is excited by the most preferred UV light with the
wavelength of 384 nm, it emits a blue-purple light of 430 nm and a
yellow light of 550 nm simultaneously, and the two emitted lights
intrinsically mix and produce a white light.
[0051] FIG. 1 shows the structure of phosphor powder I-Y or I-W
prepared in EXAMPLEs 1 and 2, which is derived from the
single-crystal X-ray diffraction analysis. They are of the
monoclinic system, and the lattice constants are as follows:
a=30.736(2) .ANG., b=13.557(1) .ANG., c=14.272(1) .ANG.;
.beta.=109.728(2).degree.. From the figure, it can be seen that the
structure is a zeolitic structure containing extra-large channels,
wherein the longest distance across the cross-section of the
channel is approximately 1.4 nm, and the shortest distance is
approximately 0.96 nm.
[0052] FIG. 2 shows the powder X-ray diffraction pattern of the
product I-Y prepared in EXAMPLE 1. It can be seen from FIG. 2 that
the product I-Y is single phase.
[0053] FIG. 3 shows the powder X-ray diffraction pattern of the
product I-W prepared in EXAMPLE 2. It can be seen from FIG. 3 that
the structure of the product I-W is identical to that of I-Y, and
it is also single phase.
[0054] FIG. 4 is the emission spectrum emitted from the product I-Y
prepared in EXAMPLE 1 when it is excited by blue light of
wavelength 494 nm, wherein yellow light having a wavelength between
520 to 650 nm is emitted.
[0055] FIG. 5 displays the excitation spectrum of product I-Y
prepared in EXAMPLE 1, and it shows that when the product I-Y is
excited by light sources of the wavelength between 280 to 500 nm, a
yellow light of the wavelength between 520 to 650 nm will be
emitted. This outcome indicates that when the phosphor powder I-Y
of the present invention is excited by blue LED, a white light can
be produced. Therefore, the product I-Y of the present invention
can be used as a substitution for the traditional fluorescent
lighting.
[0056] FIG. 6 shows the emission spectrum of product I-W prepared
in EXAMPLE 2 when it is excited by UV light of wavelength 384 nm.
The spectrum shows product I-W emits two types of light
simultaneously, one is a blue light of wavelength between 400 to
500 nm, and the other is a yellow light of wavelength between 520
to 650 nm. The results indicate that when product I-W of the
present invention is excited by UV LED, a white light can be
produced. CIE coordinates of the white light are (0.29, 0.34).
Therefore, the product I-W of the present invention can be used as
a substitution for the traditional fluorescent lighting.
[0057] FIG. 7 displays the excitation spectrum of product I-W
prepared in EXAMPLE 2, wherein there are two different types of
wavelength for the light source. When product I-W is excited by
light source of the wavelength between 270 to 420 nm, as indicated
by the solid line, a blue light of wavelength between 400 to 500 nm
will be emitted. When product I-W is excited by light source of the
wavelength between 280 to 500 nm, as indicated by the dotted line,
a yellow light of wavelength between 520 to 650 nm will be emitted.
The overlapping range of the two light sources is between 280 to
420 nm, and the best light source for white light is between 350
and 420 nm. The outcome indicates that when the phosphor powder I-W
of the present invention is excited by UV LED with long wavelength,
a white light can be produced. Even when the phosphor powder is
excited by blue LED of wavelength between 430 to 500 nm, a white
light can also be produced. These results suggest that the present
invention has wide applications, and the products of the present
invention can be used to replace the traditional fluorescent
lighting.
* * * * *