Nitride phosphors with interstitial cations for charge balance
09695357 ยท 2017-07-04
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Inventors
Cpc classification
International classification
Abstract
Phosphors comprising a nitride-based composition represented by the chemical formula: M.sub.(x/v)(M.sub.aM.sub.b)Si.sub.(cx)Al.sub.xN.sub.d:RE, wherein: M is a divalent or trivalent metal with valence v; M is at least one divalent metal; M is at least one trivalent metal; 2a+3b+4c=3d; and RE is at least one element selected from the group consisting of Eu, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb. Furthermore, the nitride-based composition may have the general crystalline structure of M.sub.aM.sub.bSi.sub.cN.sub.d, where Al substitutes for Si within the crystalline structure and M is located within the crystalline structure substantially at the interstitial sites.
Claims
1. A nitride-based phosphor comprising calcium, silicon, aluminum, nitrogen and europium, wherein said nitride-based composition has the general crystalline structure of -Si.sub.3N.sub.4, and Al substitutes for Si within said crystalline structure, and wherein said nitride-based phosphor absorbs radiation at a wavelength ranging from about 400 nm to about 480 nm and emits light with a photoluminescence peak emission wavelength within a range from about 592 nm to about 663 nm, wherein said nitride-based phosphor has a composition represented by the chemical formula Ca.sub.(1.5x0.03)(Si.sub.(1x)Al.sub.x).sub.3N.sub.4Eu.sub.0.03, where x satisfies 0.1x0.6, and calcium is located within said crystalline structure substantially at the interstitial sites.
2. The nitride-based phosphor of claim 1, wherein said orange-red nitride-based phosphor emits light having CIE(x) coordinates ranging from 0.522 to 0.688 and CIE(y) coordinates ranging from 0.473 to 0.312.
3. A nitride-based phosphor comprising strontium, silicon, aluminum, nitrogen and europium, wherein said nitride-based composition has the general crystalline structure of -Si.sub.3N.sub.4, and Al substitutes for Si within said crystalline structure, and wherein said nitride-based phosphor absorbs radiation at a wavelength ranging from about 400 nm to about 480 nm and emits light with a photoluminescence peak emission wavelength within a range from about 545 nm to about 640 nm, wherein said nitride-based phosphor has a composition represented by the chemical formula Sr.sub.(1.5x0.03)(Si.sub.(1x)Al.sub.x).sub.3N.sub.4Eu.sub.0.03, where x satisfies 0.1x0.4, and strontium is located within said crystalline structure substantially at the interstitial sites.
4. The nitride-based phosphor of claim 3, wherein said nitride-based phosphor emits light having CIE(x) coordinates ranging from 0.426 to 0.577 and CIE(y) coordinates ranging from 0.543 to 0.414.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) These and other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures, wherein:
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DETAILED DESCRIPTION OF THE INVENTION
(8) Embodiments of the present invention will now be described in detail with reference to the drawings, which are provided as illustrative examples of the invention so as to enable those skilled in the art to practice the invention. Notably, the figures and examples below are not meant to limit the scope of the present invention to a single embodiment, but other embodiments are possible by way of interchange of some or all of the described or illustrated elements. Moreover, where certain elements of the present invention can be partially or fully implemented using known components, only those portions of such known components that are necessary for an understanding of the present invention will be described, and detailed descriptions of other portions of such known components will be omitted so as not to obscure the invention. In the present specification, an embodiment showing a singular component should not be considered limiting; rather, the invention is intended to encompass other embodiments including a plurality of the same component, and vice-versa, unless explicitly stated otherwise herein. Moreover, applicants do not intend for any term in the specification or claims to be ascribed an uncommon or special meaning unless explicitly set forth as such. Further, the present invention encompasses present and future known equivalents to the known components referred to herein by way of illustration.
(9) Embodiments of the invention generally provide nitride-based phosphors and methods for forming such nitride-based phosphors. The nitride-based phosphors emit fluorescent light in at least the red, orange, and green regions of the electromagnetic spectrum. The nitride-based phosphors may be used in light emitting diode (LED) devices.
(10) In general, the present invention is based on the substitution of Si by Al in Sr.sub.2Si.sub.5N.sub.8:RE, Si.sub.3N.sub.4:RE, and related phosphor compounds, with Li, Na, K, Mg, Ca, Sr, Y, or other small metal ions and the combinations of these metal ions being incorporated substantially at the interstitial sites into the crystal lattice to provide charge balancecompensating for the charge imbalance due to substitution of Si by Al. The interstitial metal may also contribute to improved thermal and chemical stability of the crystal structure. The substitution and charge balance is effected while maintaining the same general crystal structure of the unsubstituted material. (Note that in materials science theory the vacancy density of a pure crystalline material may be on the order of a hundred parts per million of the existing lattice sites depending on the thermal equilibrium conditions of the crystal. As such, a small percentage of the charge balance ions may actually end up in vacant metal ion sites, rather than the interstitial sitesthe charge balance ions filling the vacancies before the interstitial sites.)
(11) Support for this proposed structure of the phosphor material is found in the literature for ceramic materials with an -silicon nitride crystal structure. For example, see Hampshire et al. -Sialon ceramics, Nature 274, 880 (1978) and Huang et al. Formation of -Si.sub.3N.sub.4 Solid Solutions in the System Si.sub.3N.sub.4AlNY.sub.2O.sub.3 J. Amer. Ceram. Soc. 66 (6), C-96 (1983). These articles state that it is known that the -silicon nitride unit cell contains two interstitial sites large enough to accommodate other atoms or ions. Furthermore, the -sialon structure is derived from the -silicon nitride structure by partial replacement of Si with Al, and valency compensation is effected by cationssuch as Li, Ca, Mg and Yoccupying the interstices of the (Si,Al)N network, and also by oxygen replacing nitrogen when an oxide is used. (The -sialon structure is represented by M.sub.x(Si,Al).sub.12(O,N).sub.16, where x is not greater than 2.) Yet furthermore, it is accepted that the -sialon structure requires the equivalent of at least half a cationic valency in each of the two interstices within the unit cell to stabilize the structure.
(12) Embodiments of the present invention may be described generally as phosphors comprising a nitride-based composition represented by the chemical formula: M.sub.(x/v)(M.sub.aM.sub.b)Si.sub.(cx)Al.sub.xN.sub.d:RE, wherein: M is a monovalent, divalent or trivalent metal with valence v; M is at least one divalent metal; M is at least one trivalent metal; 2a+3b+4c=3d; and RE is at least one element selected from the group consisting of Eu, Ce, Pr, Nd, Sm, Gd, Th, Dy, Ho, Er, Tm, Yb. Furthermore, the nitride-based composition may have the general crystalline structure of M.sub.aM.sub.bSi.sub.cN.sub.d, where Al substitutes for Si within the crystalline structure and M is located within the crystalline structure substantially at the interstitial sites. Yet furthermore, M may be selected from the group consisting of Li, Na, K, Ca, Sr, Mg, Ba, Zn, Sc, Y, Lu, La, Ce, Gd, Sm, Pr, Tb, and Yb, M may be selected from the group consisting of Mg, Ca, Sr, Ba, and Zn, and M may be selected from the group consisting of Sc, Y, Lu, La, Gd, Tb, Sm, Pr, Yb and Bi. Furthermore, x may satisfy 0.01x0.6c. Some examples of compositions according to embodiments of the present invention are: M.sub.x/2MSi.sub.1xAl.sub.xN.sub.2:RE; M.sub.x/2MMSi.sub.1xAl.sub.xN.sub.3:RE; M.sub.x/2MSi.sub.3xAl.sub.xN.sub.5:RE; M.sub.x/2M.sub.2MSi.sub.2xAl.sub.xN.sub.5:RE; M.sub.x/2MSi.sub.4xAl.sub.xN.sub.6:RE; M.sub.x/2M.sub.4Si.sub.3-xAl.sub.xN.sub.8:RE; M.sub.x/2M.sub.6Si.sub.3xAl.sub.xN.sub.8:RE; M.sub.x/2M.sub.3M.sub.2Si.sub.3xAl.sub.xN.sub.8:RE; M.sub.x/2M.sub.3Si.sub.3xAl.sub.xN.sub.7:RE; M.sub.x/2M.sub.3MSi.sub.3xAl.sub.xN.sub.7:RE; M.sub.x/2M.sub.2MSi.sub.5xAl.sub.xN.sub.9:RE; M.sub.x/2MM.sub.3Si.sub.4xAl.sub.xN.sub.9:RE; M.sub.x/2MSi.sub.6xAl.sub.xN.sub.9:RE; M.sub.x/2M.sub.3Si.sub.6xAl.sub.xN.sub.11:RE; and M.sub.x/2MMSi.sub.5xAl.sub.xN.sub.11:RE.
(13) Some specific embodiments of the present invention that are based on the 2-5-8 compositions (a=2, b=0, c=5 and d=8), such as Sr.sub.2Si.sub.5N.sub.8:RE, are as follows.
(14) RE.sub.x(Ca.sub.xSr.sub.(1x)).sub.(2+0.5xx)Si.sub.(5x)Al.sub.xN.sub.8 for Red and Other Phosphors
(15) In one embodiment, a phosphor (e.g., a red phosphor) containing a nitride-based compound is represented by the chemical formula Eu.sub.x(Ca.sub.xSr.sub.(1x)).sub.(2+0.5xx)Si.sub.(5x)Al.sub.xN.sub.8, (note that this formula may be rewritten in the format of the general formula, M.sub.(x/v)(M.sub.aM.sub.b)Si.sub.(cx)Al.sub.xN.sub.d:RE, as Ca.sub.0.5x(Ca.sub.xSr.sub.1x).sub.2xEu.sub.xSi.sub.5xAl.sub.xN.sub.8, similarly all formulas provided herein may be rewritten in this format) wherein 0.1x1.3, 0.00001x0.2, and 0x1, Al substitutes for Si within the crystalline structure, and the Ca charge balance cations are located within the crystalline structure substantially at the interstitial sites. In some examples, the chemical formula Eu.sub.x(Ca.sub.xSr.sub.(1x)).sub.(2+0.5x)Si.sub.(5x)Al.sub.xN.sub.8 is more narrowly represented wherein 0.3x1.3, 0.0001x0.1, and 0.05x0.4, more narrowly wherein 0.5x1.3, 0.001x0.1, and 0.1x0.3, and more narrowly wherein 0.7x1.3, for example, wherein 1.0x1.3 or wherein 1.05x1.25.
(16) The nitride-based compounds of the phosphor may have a crystalline structure with a single phase or a mixed phase and include a 2-5-8 phase in pure or mixed form. The nitride-based compounds described herein distinguish previous nitride phosphors having a 1-1-1-3 phase or CASN phase (e.g., CaSiAlN.sub.3)which generally have the space group Cmc2.sub.1. Generally, the crystalline structures of the 2-5-8 nitride-based compounds as described herein have a space group selected from Pmn2.sub.1, Cc, derivatives thereof, or mixtures thereof. In some examples, the space group is Pmn2.sub.1.
(17) In embodiments described herein, the phosphors are enabled to emit a fluorescent light at a desired or predetermined wavelength when irradiated with an excitation source. (Herein an excitation source is typically a blue excitation source having a wavelength ranging from about 420 nm to about 470, although the excitation source may have a wider range from about 250 nm to about 420 nm; a common blue excitation source is a InGaN LED, or GaN LED, emitting with a peak wavelength of about 460 nm.) The phosphor containing Eu.sub.x(Ca.sub.xSr.sub.(1x)).sub.(2+0.5xx)Si.sub.(5x)Al.sub.xN.sub.8 is generally enabled to emit a red fluorescent light, although the phosphor is also enabled to emit a fluorescent light of other colors. The fluorescent light emitted by the phosphor containing Eu.sub.x(Ca.sub.xSr.sub.(1x)).sub.(2+0.5xx)Si.sub.(5x)Al.sub.xN.sub.8 may have a peak emission wavelength within a range from about 600 nm to about 675 nm under an excitation wavelength within a range from about 400 nm to about 480 nm. In some examples, the peak emission wavelength is within a range from about 610 nm to about 640 nm, more narrowly within a range from about 620 nm to about 625 nm. In other examples, the peak emission wavelength is within a range from about 630 nm to about 660 nm, more narrowly within a range from about 640 nm to about 655 nm.
(18) In another embodiment, a phosphor (e.g., a red phosphor) containing a nitride-based compound is represented by the chemical formula RE.sub.x(Ca.sub.xSr.sub.(1x)).sub.(2+0.5xx)Si.sub.(5x)Al.sub.XN.sub.8, wherein RE is at least one element selected from Eu, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, or combinations thereof, 0.1x3, 0.00001x0.2, and 0x1, and the nitride-based compound has a crystalline structure having a space group selected from Pmn2.sub.1, Cc, derivatives thereof, or mixtures thereof, Al substitutes for Si within the crystalline structure, and the Ca charge balance cations are located within the crystalline structure substantially at the interstitial sites. A phosphor activator is represented by M which contains one element, two elements, or more elements for activating the nitride-based compound of the phosphor. In some examples, the phosphor activator contains Eu and at least one or more elements. Therefore, the M is Eu and one or more elements selected from Ce, Pr, Nd, Sm, Gd, Th, Dy, Ho, Er, Tm, Yb, or combinations thereof. In some examples, the chemical formula RE.sub.x(Ca.sub.xSr.sub.(1x)).sub.(2+0.5xx)Si.sub.(5x)Al.sub.xN.sub.8 is more narrowly represented wherein 0.3x2.5, 0.0001x0.1, and 0x1, more narrowly wherein 1x2, 0.001x0.1, and 0.05x0.4, more narrowly wherein x=2, 0.001x0.1, and 0.1x0.3.
(19) In another embodiment, a phosphor (e.g., a red phosphor) containing a nitride-based compound is represented by the chemical formula Eu.sub.x(Ca.sub.xSr.sub.(1x)).sub.(2+0.5xx)Si.sub.(5x)Al.sub.xN.sub.8, wherein 0.1x3, 0.00001x0.2, and 0x1, and the nitride-based compound has a crystalline structure having a space group selected from Pmn2.sub.1, Cc, derivatives thereof, or mixtures thereof, Al substitutes for Si within the crystalline structure, and the Ca charge balance cations are located within the crystalline structure substantially at the interstitial sites. In some examples, the chemical formula Eu.sub.x(Ca.sub.xSr.sub.(1x)).sub.(2+0.5xx)Si.sub.(5x)Al.sub.xN.sub.8 is more narrowly represented wherein 0.5x2.5, 0.0001x0.1, and 0x1, more narrowly wherein 1x2, 0.001x0.1, and 0.05x0.4, and more narrowly wherein x=2, 0.001x0.1, and 0.1x0.3. In other examples, the chemical formula Eu.sub.x(Ca.sub.xSr.sub.(1x)).sub.(2+0.5xx)Si.sub.(5x)Al.sub.xN.sub.8 is more narrowly represented wherein 0.1x1.3, 0.0001x0.1, and 0.05x0.4, and more narrowly wherein 0.51.3, 0.001x0.1, and 0.1x0.3.
(20) In another embodiment, a phosphor (e.g., a red phosphor) containing a nitride-based compound is represented by the chemical formula Eu.sub.x(Ca.sub.xSr.sub.(1x)).sub.(3x)Si.sub.3Al.sub.2N.sub.8, wherein 0.00001x0.2, and 0x1, and the nitride-based compound has a crystalline structure having a space group selected from Pmn2.sub.1, Cc, derivatives thereof, or mixtures thereof, Al substitutes for Si within the crystalline structure, and the Ca charge balance cations are located within the crystalline structure substantially at the interstitial sites. In some examples, the chemical formula Eu.sub.x(Ca.sub.xSr.sub.(1x)).sub.(3x)Si.sub.3Al.sub.2N.sub.8 is more narrowly represented wherein 0.0001x0.1, and 0.05x0.4, more narrowly wherein 0.001x0.1, and 0.1x0.3, and more narrowly wherein 0.001x0.1, and 0.1x0.3.
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(24) Some specific embodiments of the present invention that are based on the alpha silicon nitride compositions (a=0, b=0, c=3 and d=4), such as Si.sub.3N.sub.4:RE, are as follows.
(25) RE.sub.xCa.sub.(0.5xx)Si.sub.(3x)Al.sub.xN.sub.4 for Orange and Other Phosphors
(26) In another embodiment, a phosphor (e.g., an orange phosphor) containing a nitride-based compound is represented by the chemical formula RE.sub.xCa.sub.(0.5xx)Si.sub.(3x)Al.sub.xN.sub.4, wherein RE is at least one element selected from Eu, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, or combinations thereof, 0.1<x<3, and 0.0001x0.2, and wherein said nitride-based compound has the general crystalline structure of -Si.sub.3N.sub.4 (i.e. an -Si.sub.3N.sub.4 structure), Al substitutes for Si within said crystalline structure, and the Ca atoms are located within the crystalline structure substantially at the interstitial sites. In some examples, the chemical formula RE.sub.xCa.sub.(0.5xx)Si.sub.(3x)Al.sub.xN.sub.4 is more narrowly represented wherein 0.1<x<3 and 0.0001x0.2, more narrowly wherein 0.2x2 and 0.001x0.1, more narrowly wherein 0.3x1.8 and 0.005x0.1, and more narrowly wherein 0.3x1.8 and x=0.03.
(27) In many examples, the phosphor contains a nitride-based compound represented by the chemical formula Eu.sub.xCa.sub.(0.5xx)Si.sub.(3x)Al.sub.xN.sub.4, wherein 0.3x1.8 and 0.005x0.1, such as wherein 0.3x1.8 and x=0.03, and wherein said nitride-based compound has the general crystalline structure of -Si.sub.3N.sub.4, Al substitutes for Si within said crystalline structure, and the Ca atoms are located within the crystalline structure substantially at the interstitial sites. In other examples, the nitride-based compound is represented by the chemical formula Eu.sub.0.03Ca.sub.(0.5x)Si.sub.(3x)Al.sub.xN.sub.4, wherein 0.1<x<3, and wherein said nitride-based compound has the general crystalline structure of -Si.sub.3N.sub.4, Al substitutes for Si within said crystalline structure, and the Ca atoms are located within the crystalline structure substantially at the interstitial sites. In some examples, the phosphor activator contains Eu and at least one or more elements. Therefore, the RE is Eu and one or more elements selected from Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, or combinations thereof.
(28) The phosphor containing RE.sub.xCa.sub.(0.5xx)Si.sub.(3x)Al.sub.xN.sub.4 is generally enabled to emit an orange fluorescent light when irradiated with an excitation source, although the phosphor is also enabled to emit a fluorescent light of other colors. The fluorescent light emitted by the phosphor containing RE.sub.xCa.sub.(0.5xx)Si.sub.(3x)Al.sub.xN.sub.4 may have a peak emission wavelength within a range from about 570 nm to about 680 nm under an excitation wavelength within a range from about 400 nm to about 480 nm. In some examples, the peak emission wavelength is within a range from about 580 nm to about 620 nm, more narrowly within a range from about 590 nm to about 600 nm. In other examples, the peak emission wavelength is within a range from about 590 nm to about 670 nm, more narrowly within a range from about 650 nm to about 670 nm.
(29) Table 1 includes data from emission spectra of Ca.sub.((3x/2)0.03)(Si.sub.(1x)Al.sub.x).sub.3N.sub.4Eu.sub.0.03, with different x values, as described by embodiments herein. Note that Ca.sub.((3x/2)0.03)(Si.sub.(1x)Al.sub.x).sub.3N.sub.4Eu.sub.0.03, which is equivalent to Eu.sub.0.03Ca.sub.(0.5x0.03)Si.sub.(3x)Al.sub.xN.sub.4 if the x values listed in Table 1 are multiplied by 3.
(30) TABLE-US-00001 TABLE 1 Ca.sub.((3x/2)0.03)(Si.sub.1xAl.sub.x).sub.3N.sub.4Eu.sub.0.03 Sample Peak wavelength # x (nm) PL CIEx CIEy 154 0.10 592 0.89 0.522 0.473 153 0.20 599 0.97 0.546 0.451 150 0.25 598 1.05 0.547 0.450 162 0.30 599 1.09 0.554 0.443 171 0.40 652 0.70 0.592 0.406 172 0.50 663 1.09 0.637 0.362 173 0.60 663 1.54 0.688 0.312
(31) TABLE-US-00002 TABLE 2 Ca.sub.0.44(Si.sub.0.69Al.sub.0.31).sub.3N.sub.4Eu.sub.0.025 Peak wavelength D50V Sample # Eu type PL (nm) CIEx CIEy (m) 213-175-7h EuCl.sub.3 1.22 595.79 0.554 0.444 3.71 214-175-7h EuF.sub.3 1.07 598.96 0.566 0.433 4.62 213-175-14h EuCl.sub.3 1.27 595.62 0.553 0.445 5.56 214-175-14h EuF.sub.3 1.13 599.17 0.565 0.433 6.10 D50V is the median particle size of the cumulative volume distribution.
RE.sub.xSr.sub.(0.5xx)Si.sub.(3x)Al.sub.xN.sub.4 for Green and Other Phosphors
(32) In another embodiment, a phosphor (e.g., a green phosphor) containing a nitride-based compound is represented by the chemical formula RE.sub.xSr.sub.(0.5xx)Si.sub.(3x)Al.sub.xN.sub.4, wherein RE is at least one element selected from Eu, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, or combinations thereof, 0.1<x<3, and 0.0001x0.2, and wherein said nitride-based compound has the general crystalline structure of -Si.sub.3N.sub.4, Al substitutes for Si within said crystalline structure, and the Sr atoms are located within the crystalline structure substantially at the interstitial sites. In some examples, the chemical formula RE.sub.xSr.sub.(0.5xx)Si.sub.(3x)Al.sub.xN.sub.4 is more narrowly represented wherein 0.1<x<3 and 0.0001x0.2, more narrowly wherein 0.2x2 and 0.001x0.1, more narrowly wherein 0.3x1.8 and 0.005x0.1, and more narrowly wherein 0.3x1.8 and x=0.03.
(33) In many examples, the phosphor contains a nitride-based compound represented by the chemical formula Eu.sub.xSr.sub.(0.5xx)Si.sub.(3x)Al.sub.xN.sub.4, wherein 0.3x1.8 and 0.005x0.1, such as wherein 0.3x1.8 and x=0.03, and wherein said nitride-based composition has the general crystalline structure of -Si.sub.3N.sub.4, Al substitutes for Si within said crystalline structure, and the Sr atoms are located within the crystalline structure substantially at the interstitial sites. In other examples, the nitride-based compound is represented by the chemical formula Eu.sub.0.03Sr.sub.(0.5x)Si.sub.(3x)Al.sub.xN.sub.4, wherein 0.1<x<3, and wherein said nitride-based composition has the general crystalline structure of -Si.sub.3N.sub.4, Al substitutes for Si within said crystalline structure, and the Sr atoms are located within the crystalline structure substantially at the interstitial sites. In some examples, the phosphor activator contains Eu and at least one or more elements. Therefore, the RE is Eu and one or more elements selected from Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, or combinations thereof.
(34) The phosphor containing RE.sub.xSr.sub.(0.5xx)Si.sub.(3x)Al.sub.xN.sub.4 is generally enabled to emit a green fluorescent light when irradiated with an excitation source, although the phosphor is also enabled to emit a fluorescent light of other colors. The fluorescent light emitted by the phosphor containing RE.sub.xSr.sub.(0.5xx)Si.sub.(3x)Al.sub.xN.sub.4 may have a peak emission wavelength within a range from about 530 nm to about 670 nm under an excitation wavelength within a range from about 400 nm to about 480 nm. In some examples, the peak emission wavelength is within a range from about 530 nm to about 650 nm, more narrowly within a range from about 540 nm to about 595 nm. In other examples, the peak emission wavelength is within a range from about 600 nm to about 670 nm, more narrowly within a range from about 625 nm to about 650 nm.
(35) Table 3 includes data from emission spectra of Sr.sub.((3x/2)0.03)(Si.sub.(1x)Al.sub.x).sub.3N.sub.4Eu.sub.0.03 with different x values, as described by embodiments herein. Note that Sr.sub.((3x/2)0.03)(Si.sub.(1x)Al.sub.x).sub.3N.sub.4Eu.sub.0.03, which is equivalent to Eu.sub.0.03Sr.sub.(0.5x0.03)Si.sub.(3x)Al.sub.xN.sub.4 if the x values listed in Table 3 are multiplied by 3.
(36) TABLE-US-00003 TABLE 3 Sr.sub.((3x/2)0.03)(Si.sub.1xAl.sub.x).sub.3N.sub.4Eu.sub.0.03 Sample Peak wavelength # x (nm) PL CIEx CIEy 183 0.5 634 0.36 0.639 0.361 182 0.4 640 0.47 0.577 0.414 184 0.3 545 0.69 0.426 0.543 181 0.2 566 0.39 0.447 0.508 180 0.1 590 0.41 0.481 0.487
Exemplary Method for Forming Phosphors
(37) In one embodiment, the raw materials Ca.sub.3N.sub.2, AlN, Si.sub.3N.sub.4, and EuX.sub.3 (X=Cl or F) are sealed within an inert atmosphere such as nitrogen and/or argon, and maintained in such a state using a glove box. The raw materials are then weighed within the inert atmosphere, usually in a glove box, and then mixed using ordinary methods known in the art, including mixing with either a mortar or ball mill. The resulting mixture is placed in a crucible, which is then transferred to a tube furnace or a high-pressure furnace connected directly to the glove box. This is so that exposure of the mixed raw materials to an inert atmosphere is maintained. In the furnace, the mixed raw materials are heated to a temperature of about 1,400 C. to about 1,700 C. using a heating rate of about 10 C. per minute, and maintained at that temperature for a time anywhere from about 2 to about 12 hours. The sintered product is cooled to room temperature, and pulverized using known methods, including mortar, ball mill, and the like, to produce a powder with the desired composition.
(38) Exemplary synthesis processes for related nitride phosphors that may be helpful while fabricating the phosphors described herein are further disclosed in the commonly assigned U.S. application Ser. No. 12/250,400, filed Oct. 13, 2008 and published as U.S. Pub. No. 2009/0283721, which is herein incorporated by reference.
(39) Although the present invention has been particularly described with reference to certain embodiments thereof, it should be readily apparent to those of ordinary skill in the art that changes and modifications in the form and details may be made without departing from the spirit and scope of the invention.