NITRIDE NEAR-INFRARED FLUORESCENT MATERIAL AND PREPARATION METHOD AND APPLICATION THEREOF

Abstract

A nitride near-infrared fluorescent material has a general molecular formula of the nitride near-infrared fluorescent material is (Ca.sub.1-x-y-zSr.sub.xBa.sub.yEu.sub.z).sub.3[Li.sub.aMg.sub.bAl.sub.cSi.sub.d]N.sub.6. In the general molecular formula, 0≤x<1; 0≤y≤0.3; 0<z≤0.02; 3.4≤a≤4; 0≤b≤0.2; 0≤c≤0.4; 1.8≤d≤2; a+2b+3c+4d=12. The material can be adjusted and controlled to achieve a maximum emission peak wavelength of 830 nm, a maximum half-peak width of 4283 cm.sup.−1, and a quantum yield of 77%.

Claims

1. A nitride near-infrared fluorescent material, wherein a general molecular formula of the nitride near-infrared fluorescent material is (Ca.sub.1-x-y-zSr.sub.xBa.sub.yEu.sub.z).sub.3[Li.sub.aMg.sub.bAl.sub.cSi.sub.d]N.sub.6, wherein the Eu element enters a crystal site of at least one of Ca, Sr, and Ba, as a luminous element and activator, and wherein in the general molecular formula, 0≤x<1; 0≤y≤0.3; 0<z≤0.02; 3.4≤a≤4; 0≤b≤0.2; 0≤c≤0.4; 1.8≤d<2; a+2b+3c+4d=12.

2. The nitride near-infrared fluorescent material of claim 1, wherein in the general molecular formula (Ca.sub.1-x-y-zSr.sub.xBa.sub.yEu.sub.z).sub.3[Li.sub.aMg.sub.bAl.sub.cSi.sub.d]N.sub.6, 0.4≤x<1; 0≤y≤0.3; 0<z≤0.02.

3. The nitride near-infrared fluorescent material of claim 1, wherein in the general molecular formula (Ca.sub.1-x-y-zSr.sub.xBa.sub.yEu.sub.z).sub.3[Li.sub.aMg.sub.bAl.sub.cSi.sub.d]N.sub.6, 3.4≤a≤4; 0≤b≤0.2; 0≤c≤0.4; 1.8≤d≤2.

4. The nitride near-infrared fluorescent material of claim 1, wherein in the general molecular formula, x=0.699, y=0.3, z=0.001, and a=4, b=0, c=0, d=2, and wherein a peak wavelength of an emission spectrum is longest; and is 830 nm.

5. The nitride near-infrared fluorescent material of claim 4, wherein in the general molecular formula, x=0.5, y=0, z=0.001, and a=4, b=0, c=0, d=2, and wherein a half-peak width of the emission spectrum is maximum; and is 4283 cm.sup.−1.

6. The nitride near-infrared fluorescent material of claim 4, wherein in the general molecular formula, x=0.999, y=0, z=0.001, and 3.4≤a<4; 0≤b≤0.2; 0≤c≤0.4; 1.8≤d<2, and wherein half-peak widths of the emission spectrum are all greater than 3500 cm.sup.−1.

7. The nitride near-infrared fluorescent material of claim 4, wherein in the general molecular formula, x=0.999, y=0, z=0.001, and a=4, b=0, c=0, d=2, and wherein quantum efficiency of the emission spectrum is maximum; and is 77%.

8. The nitride near-infrared fluorescent material of claim 1, wherein the nitride near-infrared fluorescent material emits fluorescence with a peak in a wavelength range of 600 to 1100 nm under excitation of ultraviolet light with a wavelength of 250 to 700 nm.

9. The nitride near-infrared fluorescent material of claim 1, wherein crystals of the nitride near-infrared fluorescent material are generated in a manner of a mixture containing other crystalline or non-crystalline compounds, and wherein a mass content of the crystals of the nitride near-infrared fluorescent material in the mixture is not less than 40%.

10. The nitride near-infrared fluorescent material of claim 1, wherein the nitride near-infrared fluorescent material comprises compounds represented by one or more of following chemical formulas: (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6, (Ca.sub.0.5Sr.sub.0.499Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6, (Sr.sub.0.699Ba.sub.0.3Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6, (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3.9Al.sub.0.3Si.sub.1.5]N.sub.6, (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3.9Mg.sub.0.1Al.sub.0.1Si.sub.1.9]N.sub.6, (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3.6Al.sub.0.4Si.sub.1.5]N.sub.6, (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3.7Mg.sub.0.1Al.sub.0.3Si.sub.1.5]N.sub.6, (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3.7Mg.sub.0.2Al.sub.0.1Si.sub.1.9]N.sub.6.

11. A preparation method of the nitride near-infrared fluorescent material of claim 1, said method comprising: weighing Ca.sub.3N.sub.2 powder, Sr.sub.3N.sub.2 powder, Ba.sub.3N.sub.2 powder, Li.sub.3N powder, Mg.sub.3N.sub.2 powder, AlN powder, Si.sub.3N.sub.4 powder, and EuN and/or Eu.sub.2O.sub.3 and/or EuF.sub.3 and/or EuCl.sub.2 powder, respectively according to a stoichiometric ratio of the general molecular formula as starting materials; fully mixing the materials uniformly in a glove box filled with nitrogen atmosphere to prepare a raw material mixture; and keeping and sintering the obtained raw material mixture at a temperature range of 800-1000° C. for 2-6 hours in a nitrogen-hydrogen mixed atmosphere or a nitrogen-hydrogen-ammonia mixed atmosphere to obtain the nitride near-infrared fluorescent material.

12. The preparation method of the nitride near-infrared fluorescent material of claim 11, wherein during said weighing a particle size of the powder is at micron, sub-micron or nanometer level.

13. The preparation method of the nitride near-infrared fluorescent material of claim 11, wherein during said keeping and sintering the obtained raw material mixture the mixed atmosphere is normal pressure or micro-positive pressure, and a pressure value of the micro-positive pressure is 0-1 MPa.

14. The preparation method of the nitride near-infrared fluorescent material of claim 11, wherein during said keeping and sintering the obtained raw material mixture which is characterized in: in the step the raw material mixture is kept and sintered at a temperature range of 850-950° C. for 2-6 hours.

15. The preparation method of the nitride near-infrared fluorescent material of claim 1, wherein said keeping and sintering the obtained raw material mixture comprises: keeping sintering the obtained raw material mixture at a temperature range of 800-1000° C. for 2-6 hours in a nitrogen-hydrogen mixed atmosphere or a nitrogen-hydrogen-ammonia mixed atmosphere; and subjecting the sintered product to heat treatment at a temperature greater than 500° C. and less than 800-1000° C. for 1-10 hours in a hydrogen atmosphere to obtain the nitride near-infrared fluorescent material.

16. A light-emitting device comprising a fluorescent material and an excitation light source, wherein the fluorescent material is the nitride near-infrared fluorescent material of claim 1, and wherein a wavelength of the excitation light source is 250-700 nm.

17. (canceled)

Description

BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to explain the technical solution of the present invention more clearly, the figures will be introduced briefly below. Obviously, the following described figures merely relate to some of the embodiments of the present invention, but do not limit the present invention.

[0028] FIG. 1 is an emission spectrum diagram of Embodiments 1-7 of the present invention, of which chemical compositions are (Ca.sub.0.999Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6 (abbreviated as Ca100), (Ca.sub.0.899Sr.sub.0.1Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6 (abbreviated as Ca90Sr10), (Ca.sub.0.799Sr.sub.0.2Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6 (abbreviated as Ca80Sr20), (Ca.sub.0.699Sr.sub.0.3Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6 (abbreviated as Ca70Sr30), (Ca.sub.0.599Sr.sub.0.4Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6 (abbreviated as Ca60Sr40), (Ca.sub.0.499Sr.sub.0.5Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6 (abbreviated as Ca50Sr50), (Ca.sub.0.399Sr.sub.0.6Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6 (abbreviated as Ca40Sr60), respectively, under excitation of blue light;

[0029] FIG. 2 is an emission spectrum diagram of Embodiments 8-14 of the present invention, of which chemical compositions are (Ca.sub.0.299Sr.sub.0.7Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6 (abbreviated as Ca30Sr70), (Ca.sub.0.199Sr.sub.0.8Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6 (abbreviated as Ca20Sr80), (Ca.sub.0.099Sr.sub.0.9Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6 (abbreviated as Ca10Sr90), (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6 (abbreviated as Sr100), (Sr.sub.0.899Ba.sub.0.1Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6 (abbreviated as Sr90Ba10), (Sr.sub.0.799Ba.sub.0.2Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6 (abbreviated as Sr80Ba20), (Sr.sub.0.699Ba.sub.0.3Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6 (abbreviated as Sr80Ba20), respectively, under excitation of blue light;

[0030] FIG. 3 is a half-peak width comparison diagram of the emission spectrum of materials of Embodiments 1-14 of the present invention under excitation of blue light;

[0031] FIG. 4 is a diagram of quantum yield and absorption rate of Embodiment 11 of the present invention, of which a chemical composition is (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6, excited under different excitation wavelengths;

[0032] FIG. 5 is an excitation spectrum diagram of Embodiments 1, 11 and 14, of which chemical compositions are (Ca.sub.0.999Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6, (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6 and (Sr.sub.0.699Ba.sub.0.3Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6, respectively;

[0033] FIG. 6 is an emission spectrum diagram of Embodiments 11 and 15-16 of the present invention, of which chemical compositions are (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6, (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3.9Al.sub.0.3Si.sub.1.8]N.sub.6 and (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3.9Mg.sub.0.1Al.sub.0.1Si.sub.1.9]N.sub.6, respectively, under excitation of blue light;

[0034] FIG. 7 is an emission spectrum diagram of Embodiments 11 and 17-20 of the present invention, of which chemical compositions are (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6, (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3.8Mg.sub.0.1Si.sub.2]N.sub.6, (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3.8Al.sub.0.2Si.sub.1.9]N.sub.6, (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3.7Mg.sub.0.1Al.sub.0.3Si.sub.1.8]N.sub.6 and (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3.7Mg.sub.0.2Al.sub.0.1Si.sub.1.9]N.sub.6, respectively, under excitation of blue light;

[0035] FIG. 8 is an emission spectrum diagram of Embodiments 11 and 21-22 of the present invention, of which chemical compositions are (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6, (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3.6Mg.sub.0.2Si.sub.2]N.sub.6 and (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3.6Mg.sub.0.4Si.sub.1.8]N.sub.6, respectively, under excitation of blue light;

[0036] FIG. 9 is an emission spectrum diagram of Embodiments 11 and 23-25 of the present invention, of which chemical compositions are (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6, (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3.7Al.sub.0.1Si.sub.2]N.sub.6, (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3.6Mg.sub.0.1Al.sub.0.2Si.sub.1.9]N.sub.6 and (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3.4Al.sub.0.2Si.sub.2]N.sub.6, respectively, under excitation of blue light;

[0037] FIG. 10 is a luminescence spectrum diagram of a near-infrared light source under excitation of different currents (25-200 mA), the near-infrared light source being implemented by using Embodiment 11 and a blue light LED package of the present invention;

[0038] FIG. 11 is an optical power diagram of blue light and near-infrared light output by the Embodiment 11 and blue light LED package of the present invention under excitation of different currents (25-200 mA);

[0039] FIG. 12 is a scene diagram of the near-infrared light source of the Embodiment 11 and blue light LED package of the present invention for security imaging;

[0040] FIG. 13 is a comparison photo of imaging in a dark room without a near-infrared light source;

[0041] FIG. 14 is an emission spectrum diagram of comparative sample 1;

[0042] FIG. 15 is an emission spectrum diagram of comparative sample 2; and

[0043] FIG. 16 is an emission spectrum diagram of comparative sample 3.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0044] Definitions of some terms used in the present invention are provided below, and other unmentioned terms have definitions and meanings well known in the art. A near-infrared fluorescent material: a material having a fluorescence emission spectrum in a near-infrared band range of 700-1100 nm. In the present invention, the near-infrared fluorescent material is the nitride, of which a crystal structure is the same as that of a.sub.3[Li.sub.4Si.sub.2]N.sub.6, and a general molecular formula is: (Ca.sub.1-x-y-zSr.sub.xBa.sub.yEu.sub.z).sub.3[Li.sub.aMg.sub.bAl.sub.cSi.sub.d]N.sub.6 (0≤x<1; 0≤y≤0.3; 0<z≤0.02; 3.4≤a≤4; 0≤b≤0.2; 0≤c≤0.4; 1.8≤d≤2; a+2b+3c+4d=12). Eu element enters a crystal site of at least one of Ca, Sr and Ba as a light emitting element and activator, thereby having fluorescence characteristics. When y>0.3 and/or b>0.2 and/or c>0.4, an impurity phase will appear in a crystalline phase, resulting in decrease in luminous efficiency.

[0045] Preferably, in the general molecular formula, 0≤x<1; 0≤y≤0.3; 0<z≤0.02; more preferably, in the general molecular formula, 0.5≤x<1; 0≤y≤0.3; 0<z≤0.005. Sr element and/or Ba element are/or introduced to reduce a content of Ca element, which can achieve a significant effect of red-shifting a peak wavelength of an emission spectrum from 700 nm to 830 nm.

[0046] Preferably, in the general molecular formula, 3.4≤a≤4; 0≤b≤0.2; 0≤c≤0.4; 1.8≤d≤2. By introducing Mg element and/or Al element, a half-peak width of the emission spectrum of the material is significantly increased from 3108 to 4101 cm.sup.−1.

[0047] The nitride near-infrared fluorescent material of the present invention has the same crystal structure as the crystal structure of Ca.sub.3[Li.sub.4Si.sub.2]N.sub.6, but it reflects performances prior to the Ca.sub.3[Li.sub.4Si.sub.2]N.sub.6 material due to the changes in the elements in corresponding lattice positions in the crystal structure. Specifically, the peak wavelength of the emission spectrum has achieved significant red-shift from 700 nm to 830 nm; the half-peak width of the emission spectrum has achieved significant increase from 3195 cm.sup.−1 to 4283 cm.sup.−1; the quantum yield of the emission spectrum has been significantly improved from <20% to 77%.

[0048] In a preparation method of the nitride near-infrared fluorescent material of the present invention, raw materials adopt nitrides of respective elements, for example: Ca.sub.3N.sub.2 powder, Sr.sub.3N.sub.2 powder, Ba.sub.3N.sub.2 powder, Li.sub.3N powder, Mg.sub.3N.sub.2 powder, AlN powder, Si.sub.3N.sub.4 powder, and it needs to explain that Eu source can adopt its nitride EuN, and can also adopt Eu.sub.203, EuF.sub.3 or EuCl.sub.2 powder and the like. A temperature for sintering and holding after mixing the raw materials is 800 to 1000° C., preferably 850 to 950° C., more preferably 865 to 935° C., such as 875° C., 880° C., 890° C., 900° C., or 915° C. The product obtained by sintering can be further heat-treated at a temperature greater than 500° C. and less than 800-1000° C. in a hydrogen atmosphere for 1-10 hours to increase the relative content of Eu.sup.2 in the material.

[0049] Further, the product obtained by sintering can also be subjected to at least one method of pulverization, surface coating, and classification treatment to perform particle size adjustment and surface modification on the obtained fluorescent material. These methods can all be the same as the prior art, which can be well known by those skilled in the art, and will not be repeated here.

[0050] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments illustrated herein. The embodiments in which specific techniques or conditions are not noted, are performed according to the techniques or conditions described in the documents within the prior art or according to the product specifications. The used reagents or instruments that are not marked with manufacturers are all conventional products that can be obtained through market shopping. In the following embodiments, if not explicitly explained, “%” refers to weight percentage.

Embodiments 1-14

[0051] Embodiments 1-14 of the present invention provide fourteen nitride near-infrared fluorescent materials activated by Eu.sup.2+, of which chemical formulas are respectively: (Ca.sub.0.899Sr.sub.0.1Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6 (abbreviated as Ca90Sr10), (Ca.sub.0.799Sr.sub.0.2Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6 (abbreviated as Ca80Sr20), (Ca.sub.0.699Sr.sub.0.3Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6 (abbreviated as Ca70Sr30), (Ca.sub.0.599Sr.sub.0.4Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6 (abbreviated as Ca60Sr40), (Ca.sub.0.499Sr.sub.0.5Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6 (abbreviated as Ca50Sr50), (Ca.sub.0.399Sr.sub.0.6Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6 (abbreviated as Ca40Sr60), (Ca.sub.0.299Sr.sub.0.7Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6 (abbreviated as Ca30Sr70), (Ca.sub.0.199Sr.sub.0.8Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6 (abbreviated as Ca20Sr80), (Ca.sub.0.099Sr.sub.0.9Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6 (abbreviated as Ca10Sr90), (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6 (abbreviated as Sr100), (Sr.sub.0.899Ba.sub.0.1Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6 (abbreviated as Sr90Ba10), (Sr.sub.0.799Ba.sub.0.2Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6 (abbreviated as Sr80Ba20), (Sr.sub.0.699Ba.sub.0.3Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6 (abbreviated as Sr70Ba30).

[0052] Embodiments 1-14 of the present invention provide a preparation method of the nitride near-infrared fluorescent materials activated by Eu.sup.2+, including weighing Ca.sub.3N.sub.2 powder, Sr.sub.3N.sub.2 powder, Ba.sub.3N.sub.2 powder, Li.sub.3N powder, Si.sub.3N.sub.4 powder, and EuN powder according to stoichiometric ratio as starting materials, keeping and sintering the materials at 900° C. for 6 hours in a nitrogen-hydrogen mixed atmosphere, and furnace cooling, and taking a sample from the furnace for grinding, pulverization and subsequent related tests.

[0053] FIGS. 1 and 2 illustrate emission spectrums of materials of Embodiments 1-14 of the present invention under excitation of blue light. For Embodiments 1-11, the emission spectrum exhibits double-peak emission, the peak position of the short wavelength is at 700 nm, and the peak position of the long wavelength is located at 800 nm. As the content of Ca in the chemical composition decreases, and the content of Sr increases, the emission intensity of the peak position at 700 nm gradually decreases, and at the same time, the emission intensity of the peak position located at 800 nm gradually increases. The dominant wavelength of the emission spectrum of Embodiment 1 is at 700 nm, and the peak wavelength of the emission spectrum of Embodiment 11 is at 800 nm. As the content of Ca in the chemical composition decreases, and the content of Sr increases, the main peak wavelength gradually red shifts. For Embodiments 11-14, as the content of Sr in the chemical composition decreases, and the content of Ba increases, the main peak wavelength gradually redshifts from 800 nm to 830 nm.

[0054] FIG. 3 illustrates a half-peak width of the emission spectrum of Embodiments 1-14 of the present invention. Since the relative intensities of double-peak emissions at 700 nm and 800 nm gradually change, the half-peak width of the emission spectrum exhibits a parabolic change rule. The half-peak width of Embodiment 6 is maximum, which is 4283 cm-1.

[0055] FIG. 4 illustrates a diagram of change rule of the quantum yield and absorption rate with the excitation wavelength of Embodiment 11 of the present invention. It is not difficult to find out that the near-infrared fluorescent material has excellent absorption rate under both ultraviolet and blue excitation; Under the excitation of 250 nm ultraviolet light, the quantum yield of the near-infrared fluorescent material is up to 77%, and under the excitation of 450 nm blue light, the quantum yield is up to 40%.

[0056] FIG. 5 shows the excitation spectrum of Embodiments 1, 11 and 14 of the present invention under the monitoring of the main emission wavelength, and the near-infrared fluorescent material can be effectively excited by ultraviolet light and blue-green light.

Embodiments 15-25

[0057] Embodiments 15-25 of the present invention provide eleven nitride near-infrared fluorescent materials activated by Eu.sub.2+, of which chemical formulas are respectively: (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3.9Al.sub.0.3Si.sub.1.8]N.sub.6, (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3.9Mg.sub.0.1Al.sub.0.1Si.sub.1.9]N.sub.6, (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3.8Mg.sub.0.1Si.sub.2]N.sub.6, (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3.8Al.sub.0.2Si.sub.1.9]N.sub.6, (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3.7Mg.sub.0.1Al.sub.0.3Si.sub.1.8]N.sub.6, (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3.7Mg.sub.0.2Al.sub.0.1 Si.sub.1.9]N.sub.6, (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3.6Mg.sub.0.2Si.sub.2]N.sub.6, (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3.6Mg.sub.0.4Si.sub.1.8]N.sub.6, (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3.7Al.sub.0.1Si.sub.2]N.sub.6, (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3.6Mg.sub.0.1Al.sub.0.2Si.sub.1.9]N.sub.6, (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3.4Al.sub.0.2Si.sub.2]N.sub.6.

[0058] Embodiments 15-25 of the present invention provide a preparation method of the nitride near-infrared fluorescent materials activated by Eu.sup.2+, including weighing Sr.sub.3N.sub.2 powder, Li.sub.3N powder, Mg.sub.3N.sub.2 powder, AlN powder, Si.sub.3N.sub.4 powder, and EuN powder according to stoichiometric ratio as starting materials, keeping and sintering the materials at 900° C. for 6 hours in a nitrogen-hydrogen mixed atmosphere, furnace cooling, and taking a sample from the furnace for grinding, pulverization and subsequent related tests.

[0059] FIGS. 6-9 illustrate emission spectrums of various different materials of Embodiments 11 and 15-25 of the present invention under excitation of blue light. Compared with Embodiment 11, by replacing Li and Si with Mg and Al, the luminous intensity of the emission spectrum in the short-wavelength range can be significantly increased, thereby increasing the half-peak width of the emission spectrum. The half-peak widths of Embodiments 15-25 all are greater than 3500 cm.sup.−1. As shown in Table 1, it can be seen that the maximum half-peak width reaches 4101 cm.sup.−1.

TABLE-US-00001 TABLE 1 Fluorescent materials and their half-peak widths table Half-Peak Width (Wave Chemical Composition Number) (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6 3108 (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3.9Al.sub.0.3Si.sub.1.8]N.sub.6 4058 (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3.9Mg.sub.0.1Al.sub.0.1Si.sub.1.9]N.sub.6 4096 (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3.8Mg.sub.0.1Si.sub.2]N.sub.6 3521 (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3.6Mg.sub.0.2Si.sub.2]N.sub.6 3785 (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3.8Al.sub.0.2Si.sub.1.9]N.sub.6 3638 (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3.6Al.sub.0.4Si.sub.1.8]N.sub.6 4064 (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3.7Mg.sub.0.1Al.sub.0.3Si.sub.1.8]N.sub.6 4008 (Sr.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3.7Mg.sub.0.2Al.sub.0.1Si.sub.1.9]N.sub.6 4101

[0060] FIG. 10 illustrates a luminescence spectrum diagram of a near-infrared light source under excitation of different currents (25-200 mA), the near-infrared light source being implemented by Embodiment 11 and a blue light LED package of the present invention, and the near-infrared emission spectrum covering an entire near-infrared optical spectrum range from 600 to 1000 nm.

[0061] FIG. 11 is an optical power diagram of blue light and near-infrared light of the near-infrared light source under excitation of different currents (25-200 mA), the near-infrared light source being implemented by the Embodiment 11 and blue light LED package of the present invention, and the output near-infrared optical power is up to 41 mW when the input current is 200 mA.

[0062] FIGS. 12-13 illustrate applications of the near-infrared light source implemented by the Embodiment 11 and blue light LED chip package of the present invention in the security field: FIGS. 12 and 13 are respectively photos obtained by using a near-infrared camera in dark rooms with a near-infrared light source and without a light source to illustrate application potential of the near-infrared light source obtained by package in the security field.

INDUSTRIAL APPLICABILITY

[0063] The nitride near-infrared fluorescent material of the present invention has simple process, easy-to-obtain raw materials and low cost. The prepared nitride near-infrared fluorescent material has many advantages such as high quantum yield, effective excitation by blue light, large emission spectrum half-peak width and the like, and can be used in security, health monitoring and other fields as a near-infrared light source. It can be expected that the series of near-infrared fluorescent materials and the preparation method thereof of the present invention can be widely used, which greatly promotes the development of the near-infrared light source industry and its application fields.

Comparative Examples 1-3

[0064] The present Comparative Examples 1-3 provide three comparative fluorescent materials, of which chemical formulas are respectively: (Ca.sub.0.999Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6, (Ca.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3Al.sub.3]N.sub.6 and (Sr.sub.0.999Eu.sub.0.001).sub.3[Mg.sub.6]N.sub.6, and a preparation method of three comparative fluorescent materials is: weighing nitride powders of various elements according to stoichiometric ratio as starting materials, keeping and sintering the materials at 900° C. for 6 hours in a nitrogen-hydrogen mixed atmosphere, furnace cooling, and taking a sample from the furnace for grinding, pulverization and subsequent related tests.

[0065] Referring to FIGS. 14, 15 and 16 for emission spectrums of three comparative fluorescent materials, peak wavelengths of the emission spectrums of (Ca.sub.0.999Eu.sub.0.001).sub.3[Li.sub.4Si.sub.2]N.sub.6, (Ca.sub.0.999Eu.sub.0.001).sub.3[Li.sub.3Al.sub.3]N.sub.6 and (Sr.sub.0.999Eu.sub.0.001).sub.3[Mg.sub.6]N.sub.6 are at 700 nm, 592 nm and 607 nm, respectively. Accordingly, the three comparative fluorescent materials provided by Comparative Examples 1-3 cannot satisfy the requirement that the peak wavelength of the near-infrared fluorescent material is in the range of 700-1100 nm.

[0066] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above-mentioned embodiments. Various simple transformations can be made to the technical solution of the present invention within the scope of the technical concept of the present invention. These simple transformations all belong to the protection scope of the present invention.

[0067] In addition, it needs to explain that the specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, various possible combinations are not explained separately in the present invention.

[0068] In addition, various different embodiments of the present invention can also be combined arbitrarily, as long as they do not violate the idea of the present invention, and they should also be regarded as the contents disclosed by the present invention.