Cr < 3 + >-activated near-infrared fluorescent powder as well as preparation method and application thereof

Abstract

The invention discloses Cr < 3 + > activated near-infrared fluorescent powder as well as a preparation method and application thereof, and the chemical formula of the near-infrared fluorescent powder is CsGa < 2-x > P5O16: xCr < 3 + >, and x is less than or equal to 1.3. The CsGa2-xP5O16: xCr < 3 + > near-infrared fluorescent powder is converted into near-infrared light within the range of 700-1100 nm through efficient excitation of blue light and red light, the half-peak width exceeds 180 nm, and the typical near-infrared I-region luminescence characteristic is shown. The near-infrared fluorescent powder disclosed by the invention has relatively high luminous intensity, wide emission range, excellent stability and wide half-peak width, can meet the application requirements of near-infrared functional materials, can be used for constructing an efficient near-infrared light source, can realize broadband near-infrared emission under the excitation of blue light and red light chips, and has wide application prospects. The light source has wide application potential in the fields of night vision imaging and biological penetration imaging.

Description

Technical Field

[0001] The present invention relates to a near-infrared phosphor, and more particularly to a Cr 3+ -activated near-infrared phosphor and its preparation method and application. Background Art

[0002] In recent years, near-infrared emitting phosphors have become a research hotspot in the scientific community due to their wide application potential in multiple fields such as information encryption, plant growth promotion, food and drug safety detection, and bioimaging. Traditional light sources such as halogen tungsten lamps can provide broadband emission from visible light to the near-infrared region, but due to their large volume, high energy consumption, and high cost, they are not suitable for the needs of portable devices. In contrast, near-infrared laser diodes have the advantages of miniaturization, long life, and low energy consumption, but their emission spectral band is narrow (the full width at half maximum is usually not more than 50 nm), which limits their application in scenarios requiring broadband emission or multi-spectral bands. Therefore, current research focuses on developing near-infrared light sources that are miniaturized, low-energy-consuming, have reasonable costs, and have broadband emission characteristics to meet the increasingly diverse application requirements.

[0003] The light-emitting diode (LED) technology based on near-infrared phosphor conversion is becoming a research hotspot. By using mature ultraviolet, blue, or red LEDs as excitation sources, near-infrared phosphors can be efficiently excited to achieve broadband emission, which provides an effective path for the development of new near-infrared light sources. Among existing near-infrared luminescent materials, transition metal ions and rare earth ions are commonly used activators. In particular, Cr 3+ ions, due to their excellent optical properties, have become the focus of research. The absorption peak of Cr 3+ ions in the blue region can match the currently widely used InGaN blue LEDs, and their emission wavelength range covers 700 - 1000 nm, showing excellent broadband luminescence characteristics. The luminescence characteristics of Cr 3+ are significantly affected by the local crystal field strength: in a strong crystal field, Cr 3+ ions usually exhibit 2 E→ 4 A2 spin-forbidden narrow-band emission; while in a weak crystal field, it is mainly 4 T2→ 4 A2 spin-allowed broadband emission. By regulating the local crystal field environment of Cr 3+ , broadband near-infrared spectral emission can be achieved. However, currently, the emission wavelengths of most Cr 3+ -activated phosphors still focus on below 800 nm, and the full width at half maximum is usually less than 120 nm, which limits their use in some high-demand application scenarios. Therefore, how to further broaden the emission spectral width of Cr 3+ -activated phosphors has become the key to technological development.

[0004] It should be noted that the information disclosed in the above background art section is only used to enhance the understanding of the background of the present disclosure, and thus may include information that does not constitute the prior art known to those of ordinary skill in the art. Summary of the Invention

[0005] The object of the present invention is to provide a Cr 3+ -activated near-infrared phosphor and its preparation method and application, which solve the problems of narrow half-peak width, poor thermal stability and insufficient purity of the synthesis process existing in the existing near-infrared emitting phosphors, and can achieve broadband near-infrared emission of high-purity single-phase Cr 3+ -activated phosphors. At the same time, the preparation method provided by the present invention has the advantages of simple process, energy saving and high efficiency, and strong repeatability, significantly enhancing the practical application potential of the near-infrared phosphor.

[0006] To achieve the above object, the present invention provides a Cr 3+ -activated near-infrared phosphor, and the chemical formula of the near-infrared phosphor is CsGa 2-x P5O 16 :xCr 3+ , where 0.1 < x ≤ 1.3. x can be selected from 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, etc. Only a part is listed here, but it is not limited to this, and any value within 0.1 < x ≤ 1.3 is acceptable.

[0007] Preferably, 0.3 ≤ x ≤ 1.3. x can be selected from 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, etc. Only a part is listed here, but it is not limited to this, and any value within 0.3 ≤ x ≤ 1.3 is acceptable.

[0008] More preferably, 0.3 ≤ x ≤ 0.9. x can be selected from 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, etc. Only a part is listed here, but it is not limited to this, and any value within 0.3 ≤ x ≤ 0.9 is acceptable.

[0009] Even more preferably, 0.3 ≤ x ≤ 0.7. x can be selected from 0.3, 0.4, 0.5, 0.6, 0.7, etc. Only a part is listed here, but it is not limited to this, and any value within 0.3 ≤ x ≤ 0.7 is acceptable.

[0010] Preferably, the chemical formula of the near-infrared phosphor is CsGa 1.7 P5O 16 :0.3Cr 3+ 、CsGa 1.5 P5O 16 :0.5Cr3+ , CsGa 1.3 P5O 16 :0.7Cr 3+ , CsGa 1.1 P5O 16 :0.9Cr 3+ or CsGa 0.7 P5O 16 :1.3Cr 3+ .

[0011] Preferably, the near-infrared phosphor has an excitation wavelength range of 370 to 800 nm, and an emission wavelength range of 700 to 1100 nm.

[0012] The second object of the present invention is to provide the Cr 3+ A method for preparing an activated near-infrared phosphor, the method comprising the following steps:

[0013] (1) grinding a cesium-containing compound, a gallium-containing compound, ammonium dihydrogen phosphate, and a chromium-containing compound to obtain a mixture;

[0014] (2) placing the mixture into a crucible and transferring it to a muffle furnace, heating it to 300-500° C. at a heating rate of 5° C. / min in an air atmosphere and keeping the temperature for 2-5 hours to obtain a pre-sintered bulk precursor;

[0015] (3) grinding the cooled bulk precursor, heating it to 700-900° C. in a muffle furnace under air atmosphere at a heating rate of 5° C. / min and keeping the temperature for 8-14 h to obtain a product after the first calcination reaction;

[0016] (4) taking out the cooled product and grinding it into powder, heating it to 700-900° C. in a muffle furnace under air atmosphere at a heating rate of 5° C. / min and keeping it at that temperature for 8-14 h to obtain a product after the second calcination reaction;

[0017] (5) Wait for the reaction to be completed, cool the temperature naturally to room temperature, and post-treat the obtained product to obtain Cr 3+ Activate near-infrared phosphors.

[0018] Preferably, the cesium-containing compound is selected from Cs2CO3, the gallium-containing compound is selected from Ga2O3, and the chromium-containing compound is selected from Cr2O3; or / and, the post-treatment is sequentially crushing, grinding, washing with anhydrous ethanol, filtering, drying and grinding.

[0019] Preferably, for the first calcination, it is heated to 800 °C at a heating rate of 5 °C / min in a muffle furnace under an air atmosphere and held for 12 h; for the second calcination, it is heated to 800 °C at a heating rate of 5 °C / min in a muffle furnace under an air atmosphere and held for 12 h.

[0020] Preferably, during the pre-calcination process, it is heated to 400 °C at a heating rate of 5 °C / min in an air atmosphere and held for 4 h.

[0021] The third object of the present invention is to provide the application of the described Cr 3+ activated near-infrared phosphor as a near-infrared light source.

[0022] Preferably, the excitation wavelength range of the described Cr 3+ activated near-infrared phosphor is 370 - 800 nm, which can match blue or red light-emitting diodes.

[0023] Preferably, the near-infrared light source contains the described Cr 3+ activated near-infrared phosphor and a blue light-emitting diode with a luminous wavelength of 380 - 500 nm or a red light-emitting diode with a luminous wavelength of 620 - 700 nm, and is applied in the fields of night vision imaging and biological penetration imaging.

[0024] Preferably, the emission wavelength range of the described Cr 3+ activated near-infrared phosphor is 700 - 1100 nm, covering the near-infrared I region.

[0025] The Cr 3+ activated near-infrared phosphor of the present invention, its preparation method and application have the following advantages:

[0026] (1) The CsGa 2-x P5O 16 :xCr 3+ near-infrared phosphor of the present invention, through the efficient excitation of blue and red light, converts it into near-infrared light in the range of 700 - 1100 nm. The Cr 3+ ions in the crystal structure are in a weak crystal field environment, 4 T2→ 4 the spin-allowed transition of A2 enables it to generate near-infrared emission at 922 - 940 nm under blue light excitation, and at the same time exhibits a super broadband emission in the range of 700 - 1100 nm, with a full width at half maximum exceeding 180 nm, presenting typical near-infrared I region luminescence characteristics;

[0027] (2) The near-infrared phosphor of the present invention can achieve efficient broadband near-infrared emission under 460 nm blue light excitation, fully meeting the application requirements of near-infrared conversion type light-emitting diodes;

[0028] (3) The near-infrared phosphor of the present invention has high luminescence intensity, a wide emission range, excellent stability, and a wide full-width at half-maximum, and can meet the application requirements of near-infrared functional materials;

[0029] (4) The near-infrared phosphor of the present invention can be used to construct an efficient near-infrared light source, which can achieve broadband near-infrared emission under the excitation of blue and red chips. This light source has broad application potential in the fields of non-destructive testing, plant growth promotion, night vision monitoring, information encryption, infrared remote control, temperature sensing, and food safety detection;

[0030] (5) The preparation method of the present invention can successfully introduce Cr ions into the CsGa2P5O 16 matrix to achieve broadband near-infrared luminescence performance. The whole process is environmentally friendly and easy to operate; by optimizing the concentration, reaction temperature, and time of the doping ions (Cr 3+ ), broadband near-infrared optimal emission is achieved, and excellent thermal stability is also exhibited. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 X-ray diffraction patterns of CsGa 2-x P5O 16 :xCr 3+ , 0.1≤x≤0.9 prepared in Examples 1-4 and Comparative Example 2 of the present invention.

[0032] Figure 2 Scanning electron micrograph (SEM) of CsGa 1.3 P5O 16 :0.7Cr 3+ prepared in Example 3 of the present invention.

[0033] Figure 3 Emission spectrum of CsGa 1.3 P5O 16 :0.7Cr 3+ prepared in Example 3 of the present invention.

[0034] Figure 4 Excitation spectrum of CsGa 1.3 P5O 16 :0.7Cr 3+ prepared in Example 3 of the present invention.

[0035] Figure 5 Emission spectra of CsGa 2-x P5O 16 :xCr 3+ , 0.1≤x≤0.9 prepared in Examples 1-4 and Comparative Example 2 of the present invention.

[0036] Figure 6Emission spectrogram of the materials prepared in Example 3, Example 5 and Example 6 of the present invention.

[0037] Figure 7 CsGa prepared according to the present invention and Comparative Example 1 1.3 P5O 16 :0.7Cr 3+ X-ray diffraction pattern.

[0038] Figure 8 CsGa prepared in Comparative Example 2 and Comparative Example 3 of the present invention 1.9 P5O 16 :0.1Cr 3+ and CsGa 1.95 P5O 16 :0.05Cr 3+ Emission spectrogram.

[0039] Figure 9 CsGa prepared in Example 4 and Comparative Example 4 of the present invention 1.1 P5O 16 :0.9Cr 3+ and CsGa 0.7 P5O 16 :1.3Cr 3 + Emission spectrogram.

[0040] Figure 10 Thermal stability diagram of CsGa prepared in Example 3 of the present invention 1.3 P5O 16 :0.7Cr 3+

[0041] Figure 11 Emission spectrogram and physical diagram of the device after LED packaging of CsGa prepared in Example 3 of the present invention 1.3 P5O 16 :0.7Cr 3+

[0042] Figure 12 Application diagram of the device after LED packaging of CsGa prepared in Example 3 of the present invention in the field of night vision imaging; A is a photo of an item under a fluorescent lamp captured by a camera; B is a photo captured by a near-infrared camera after turning on a near-infrared LED device in a dark environment. 1.3 P5O 16 :0.7Cr 3+ Detailed implementation mode

[0043] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0044] It should be noted that: for those not specified with specific conditions in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. For those instruments not specified with the manufacturer, they are all conventional products that can be obtained through commercial purchase. For those raw materials and reagents not specified with the manufacturer, they are all commercially available products or can be prepared by known methods.

[0045] In the present invention, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are only for the sake of simplicity and convenience. Accordingly, the description of the numerical range or percentage range should be regarded as having covered and specifically disclosed all possible sub-ranges and individual numerical values within the range (including integers and fractions).

[0046] The features mentioned in the present invention can be combined arbitrarily as long as there is no contradiction in the combination of these features. All possible combinations should be considered as within the scope described in this specification. Each feature disclosed in the specification can be replaced by any alternative feature that can provide the same, equivalent, or similar purpose. Therefore, unless otherwise specified, the disclosed features are only general examples of equivalent or similar features.

[0047] Example 1

[0048] A Cr 3+ -activated near-infrared phosphor with the chemical formula CsGa 1.7 P5O 16 :0.3Cr 3+ , and its preparation method is as follows:

[0049] Weigh cesium compounds, gallium compounds, ammonium dihydrogen phosphate, and chromium compounds in a molar ratio of 0.5∶0.85∶5∶0.15. Specifically, weigh 0.4888 g of Cs2CO3 (99.9%), 0.4780 g of Ga2O3 (99.995%), 1.7255 g of NH4H2PO4 (99.5%), and 0.0684 g of Cr2O3 (99.95%), for a total of 2.7607 g. Grind the raw materials thoroughly and mix them evenly. Transfer the mixed raw materials into an alumina crucible and then move it to a muffle furnace for pre-calcination. Heat it to 400 °C at a heating rate of 5 °C / min in an air atmosphere, hold for 4 h, and then cool to room temperature. Take out the bulk sample cooled to room temperature, grind it, and conduct the first calcination. Heat it to 750 °C at a heating rate of 5 °C / min in a muffle furnace in an air atmosphere, hold for 13 h, and then cool to room temperature. Take out the cooled product, grind it into powder again, and conduct the second calcination. Heat it to 750 °C at a heating rate of 5 °C / min in a muffle furnace in an air atmosphere and hold for 13 h. After the reaction, naturally cool it to room temperature. The obtained product is ground, rinsed 3 times with absolute ethanol, filtered, dried, and ground. Finally, a kind of Cr 3+ activated broadband near-infrared phosphor CsGa 1.7 P5O 16 :0.3Cr 3+ .

[0050] Example 2

[0051] A kind of Cr 3+ activated near-infrared phosphor with the chemical formula CsGa 1.5 P5O 16 :0.5Cr 3+ , and its preparation method is as follows:

[0052] Weigh cesium compounds, gallium compounds, ammonium dihydrogen phosphate, and chromium compounds in a molar ratio of 0.5∶0.75∶5∶0.25. Specifically, weigh 0.4888 g of Cs2CO3 (99.9%), 0.4217 g of Ga2O3 (99.995%), 1.7255 g of NH4H2PO4 (99.5%), and 0.1140 g of Cr2O3 (99.95%), for a total of 2.7500 g. Grind the raw materials thoroughly and mix them evenly. Transfer the mixed raw materials into an alumina crucible and then move it to a muffle furnace for pre-calcination. Heat it to 400 °C at a heating rate of 5 °C / min in an air atmosphere, hold for 4 h, and then cool to room temperature. Take out the cooled bulk sample, grind it, and conduct the first calcination. Heat it to 800 °C at a heating rate of 5 °C / min in a muffle furnace in an air atmosphere, hold for 13 h, and then cool to room temperature. Take out the cooled product, grind it into powder again, and conduct the second calcination. Heat it to 800 °C at a heating rate of 5 °C / min in a muffle furnace in an air atmosphere and hold for 13 h. After the reaction is completed, cool it to room temperature naturally. The obtained product is ground, rinsed with absolute ethanol three times, filtered, dried, and ground. Finally, a kind of Cr 3+ activated broadband near-infrared phosphor CsGa 1.5 P5O 16 :0.5Cr 3+ is obtained.

[0053] Example 3

[0054] A kind of Cr 3+ activated near-infrared phosphor with the chemical formula CsGa 1.3 P5O 16 :0.7Cr 3+ , and its preparation method is as follows:

[0055] Weigh cesium compounds, gallium compounds, ammonium dihydrogen phosphate, and chromium compounds in a molar ratio of 0.5∶0.65∶5∶0.35. Specifically, weigh 0.4888 g of Cs2CO3 (99.9%), 0.3655 g of Ga2O3 (99.995%), 1.7255 g of NH4H2PO4 (99.5%), and 0.1596 g of Cr2O3 (99.95%), for a total of 2.7394 g. Grind the raw materials thoroughly and mix them evenly. Transfer the mixed raw materials into an alumina crucible and then move it to a muffle furnace for pre-calcination. Heat it to 400 °C at a heating rate of 5 °C / min in an air atmosphere, hold for 4 h, and then cool to room temperature. Take out the block sample cooled to room temperature, grind it, and conduct the first calcination. Heat it to 800 °C at a heating rate of 5 °C / min in a muffle furnace in an air atmosphere, hold for 12 h, and then cool to room temperature. Take out the cooled product, grind it into powder again, and conduct the second calcination. Heat it to 800 °C at a heating rate of 5 °C / min in a muffle furnace in an air atmosphere and hold for 12 h. After the reaction, naturally cool to room temperature. The obtained product is ground, rinsed with anhydrous ethanol three times, filtered, dried, and ground. Finally, a kind of Cr 3+ activated broadband near-infrared phosphor CsGa 1.3 P5O 16 :0.7Cr 3+ is obtained.

[0056] Example 4

[0057] A kind of Cr 3+ activated near-infrared phosphor with the chemical formula CsGa 1.1 P5O 16 :0.9Cr 3+ , and its preparation method is as follows:

[0058] Weigh cesium compounds, gallium compounds, ammonium dihydrogen phosphate, and chromium compounds in a molar ratio of 0.5∶0.55∶5∶0.45. Specifically, weigh 0.4888 g of Cs2CO3 (99.9%), 0.3093 g of Ga2O3 (99.995%), 1.7255 g of NH4H2PO4 (99.5%), and 0.2052 g of Cr2O3 (99.95%), for a total of 2.7288 g. Grind the raw materials thoroughly and mix them evenly. Transfer the mixed raw materials into an alumina crucible and then move it to a muffle furnace for pre-calcination. Heat it to 400 °C at a heating rate of 5 °C / min in an air atmosphere, hold for 4 h, and then cool to room temperature. Take out the block sample cooled to room temperature, grind it, and conduct the first calcination. Heat it to 900 °C at a heating rate of 5 °C / min in a muffle furnace in an air atmosphere, hold for 8 h, and then cool to room temperature. Take out the cooled product, grind it into powder again, and conduct the second calcination. Heat it to 900 °C at a heating rate of 5 °C / min in a muffle furnace in an air atmosphere, and hold for 8 h. After the reaction, naturally cool to room temperature. The obtained product is ground, rinsed with anhydrous ethanol three times, filtered, dried, and ground. Finally, a kind of Cr 3+ Activated broadband near-infrared phosphor CsGa 1.1 P5O 16 :0.9Cr 3+ .

[0059] Example 5

[0060] A kind of Cr 3+ Activated near-infrared phosphor, with the same chemical formula as in Example 3, which is CsGa 1.3 P5O 16 :0.7Cr 3+ , and its preparation method is basically the same as that of Example 3, except that:

[0061] Pre-calcine by heating to 300 °C and holding for 2 h.

[0062] Example 6

[0063] A kind of Cr 3+ Activated near-infrared phosphor, with the same chemical formula as in Example 3, which is CsGa 1.3 P5O 16 :0.7Cr 3+ , and its preparation method is basically the same as that of Example 3, except that:

[0064] Pre-calcine by heating to 500 °C and holding for 5 h.

[0065] Comparative Example 1

[0066] A kind of Cr 3+The activated near-infrared phosphor has the same chemical formula as that in Example 3, which is CsGa 1.3 P5O 16 :0.7Cr 3 + , and its preparation method is basically the same as that of Example 3, except that:

[0067] There is no pre-calcination, and the subsequent two calcination processes are directly carried out by heating to 800 °C.

[0068] Comparative Example 2

[0069] A Cr 3+ activated near-infrared phosphor with the chemical formula CsGa 1.9 P5O 16 :0.1Cr 3+ , and its preparation method is as follows:

[0070] Weigh the cesium compound, gallium compound, ammonium dihydrogen phosphate, and chromium compound in a molar ratio of 0.5∶0.95∶5∶0.05. Specifically, weigh 0.4888 g of Cs2CO3 (99.9%), 0.5342 g of Ga2O3 (99.995%), 1.7255 g of NH4H2PO4 (99.5%), and 0.0228 g of Cr2O3 (99.95%), totaling 2.7713 g. Grind the raw materials thoroughly and mix them evenly. Transfer the mixed raw materials into an alumina crucible and then to a muffle furnace for pre-calcination. Heat it to 400 °C at a heating rate of 5 °C / min in an air atmosphere, and keep it for 4 h, then cool it to room temperature. Take out the block sample cooled to room temperature, grind it, and conduct the first calcination. Heat it to 700 °C at a heating rate of 5 °C / min in an air atmosphere in the muffle furnace, and keep it for 14 h, then cool it to room temperature. Take out the cooled product, grind it into powder again, and conduct the second calcination. Heat it to 700 °C at a heating rate of 5 °C / min in an air atmosphere in the muffle furnace, and keep it for 14 h. After the reaction, naturally cool it to room temperature. The obtained product is ground, rinsed with anhydrous ethanol 3 times, filtered, dried, and ground to finally obtain a Cr 3+ activated broadband near-infrared phosphor CsGa 1.9 P5O 16 :0.1Cr 3+ .

[0071] Comparative Example 3

[0072] A Cr 3+ activated near-infrared phosphor with the chemical formula CsGa 1.95 P5O 16 :0.05Cr 3+ , and its preparation method is as follows:

[0073] Weigh a cesium compound, a gallium compound, ammonium dihydrogen phosphate and a chromium compound in a molar ratio of 0.5∶0.975∶5∶0.025. Specifically, weigh 0.4888 g of Cs2CO3 (99.9%), 0.5483 g of Ga2O3 (99.995%), 1.7255 g of NH4H2PO4 (99.5%) and 0.0114 g of Cr2O3 (99.95%), for a total of 2.7740 g. Grind the raw materials thoroughly and mix them evenly. Transfer the mixed raw materials into an alumina crucible and then transfer it to a muffle furnace for pre-calcination. Heat it to 400 °C at a heating rate of 5 °C / min in an air atmosphere, hold for 4 h, and then cool to room temperature. Take out the block sample cooled to room temperature, grind it, and perform the first calcination. Heat it to 700 °C at a heating rate of 5 °C / min in a muffle furnace in an air atmosphere, hold for 14 h, and then cool to room temperature. Take out the cooled product, grind it into powder again, and perform the second calcination. Heat it to 700 °C at a heating rate of 5 °C / min in a muffle furnace in an air atmosphere, and hold for 14 h. After the reaction is completed, cool it to room temperature naturally. The obtained product is ground, rinsed 3 times with anhydrous ethanol, filtered, dried, and ground to finally obtain a kind of Cr 3+ -activated broadband near-infrared phosphor CsGa 1.95 P5O 16 :0.05Cr 3+ .

[0074] Comparative Example 4

[0075] A kind of Cr 3+ -activated near-infrared phosphor with the chemical formula CsGa 0.7 P5O 16 :1.3Cr 3+ , and its preparation method is as follows:

[0076] Weigh cesium compounds, gallium compounds, ammonium dihydrogen phosphate, and chromium compounds in a molar ratio of 0.5∶0.35∶5∶0.65. Specifically, weigh 0.4888 g of Cs2CO3 (99.9%), 0.3093 g of Ga2O3 (99.995%), 1.7255 g of NH4H2PO4 (99.5%), and 0.2305 g of Cr2O3 (99.95%), for a total of 2.7541 g. Grind and mix the raw materials thoroughly. Load the mixed raw materials into an alumina crucible and transfer it to a muffle furnace for pre-calcination. Heat it to 400 °C at a heating rate of 5 °C / min in an air atmosphere, hold for 4 h, and then cool to room temperature. Take out the bulk sample cooled to room temperature, grind it, and perform the first calcination. Heat it to 900 °C at a heating rate of 5 °C / min in an air atmosphere in the muffle furnace, hold for 8 h, and then cool to room temperature. Take out the cooled product, grind it into powder again, and perform the second calcination. Heat it to 900 °C at a heating rate of 5 °C / min in an air atmosphere in the muffle furnace and hold for 8 h. After the reaction, cool it naturally to room temperature. The obtained product is ground, rinsed 3 times with absolute ethanol, filtered, dried, and ground. Finally, a kind of Cr 3+ Activated broadband near-infrared phosphor CsGa 0.7 P5O 16 :1.3Cr 3+ .

[0077] Experimental Example 1 Structure Characterization

[0078] The structure of the near-infrared phosphor prepared in the examples of the present invention was characterized by an X-ray diffractometer (DX-2700BH).

[0079] As Figure 1 shown, it is the X-ray diffraction pattern of the near-infrared phosphors prepared in Examples 1-4 and Comparative Example 2 of the present invention. From Figure 1 it can be observed that the X-ray diffraction spectrum of the near-infrared fluorescent phosphor is consistent with the PDF card of the standard spectrum. The strongest peak is at a 2θ angle of 30.78°, corresponding to the (-221) crystal plane of the CsGa2P5O 16 standard card. Moreover, from Figure 1 the XRD test results, it can be seen that the near-infrared phosphors prepared in Examples 1-4 and Comparative Example 2 of the present invention have few impurity phases and high purity.

[0080] As Figure 2 shown, it is the SEM image of the CsGa 1.3 P5O 16 :0.7Cr 3+ phosphor prepared in Example 3 of the present invention. It can be seen from the figure that the phosphor shows a micron-sized block morphology, and the diameter distribution is 50-150 μm.

[0081] As Figure 7 shown, it is the X-ray diffraction pattern of the near-infrared phosphor prepared in Comparative Example 1 of the present invention. From Figure 7 it can be observed that the positions of the peaks in the X-ray diffraction spectrum of the near-infrared fluorescent phosphor are basically the same as those of the PDF card of the standard spectrum, but its strongest peak (2θ = 25.68°) is different from the strongest peak (2θ = 30.78°) of the spectrum of Example 3 and the standard PDF card, indicating that the lack of pre-firing has an impact on the crystal structure and purity of the phosphor.

[0082] Experimental Example 2 Optical Property Characterization

[0083] The emission spectrum of the near-infrared phosphor prepared in the examples of the present invention was tested using a steady-state and transient spectrometer (FLS-1000) from Edinburgh.

[0084] As Figure 3 shown, it is the emission spectrum of the CsGa 1.3 P5O 16 :0.7Cr 3+ phosphor prepared in Example 3 of the present invention. It can be seen from the figure that the phosphor shows a near-infrared emission at 924 nm with a full width at half maximum of 182 nm.

[0085] As Figure 4 shown, it is the excitation spectrum of the near-infrared phosphor prepared in Example 3 of the present invention. The results show that the obtained near-infrared phosphor can be effectively excited between 380 - 500 nm and 620 - 700 nm.

[0086] As Figure 5 shown, it is the emission spectrum of the near-infrared phosphors prepared in Examples 1 - 4 and Comparative Example 2 of the present invention. The results show that the emission spectrum range of the obtained near-infrared phosphors is between 700 - 1100 nm, the emission peak is located at 922 - 940 nm, the full width at half maximum exceeds 180 nm, the emission peak band is relatively wide, and the fluorescence intensity is affected by the concentration of added Cr 3+ . When the value of x is between 0.3 and 0.7, with the increase of the added amount of Cr 3+ , the fluorescence intensity increases significantly, while when x = 0.1 and 0.9, the fluorescence intensity decreases, especially when x = 0.1. This may be because when Cr exceeds 0.9, too much Cr will cause the phenomenon of "fluorescence quenching", that is, the luminescence intensity gradually decreases until it disappears with the increase of the Cr 3+ concentration. As an activator, when the added amount is too small, the activation of the matrix material CsGa2P5O 3+ has a poor luminescence effect. 16

[0087] As Figure 6As shown, the emission spectra of the near-infrared phosphors prepared in Example 3, Example 5, and Example 6 of the present invention are presented, where ① corresponds to Example 3, ② corresponds to Example 5, and ③ corresponds to Example 6. It can be seen from the figure that the emission intensity of Example 3 is the highest, indicating that the pre-sintering temperature and duration have an impact on the luminescence intensity of the phosphor.

[0088] As Figure 8 shown, the emission spectra of the near-infrared phosphors prepared in Comparative Example 2 and Comparative Example 3 of the present invention are presented. The results show that the fluorescence intensity of Comparative Example 3 is significantly lower than that of Comparative Example 2, indicating that the lower the value of x, the worse the fluorescence intensity. In the case of x = 0.1 compared to x = 0.05, the phosphor can maintain relatively strong fluorescence emission.

[0089] As Figure 9 shown, the emission spectra of the near-infrared phosphors prepared in Example 4 and Comparative Example 4 of the present invention are presented. The results show that the fluorescence intensity of Comparative Example 4 is significantly lower than that of Example 4, indicating that x ≤ 0.9 can maintain strong fluorescence emission of the phosphor.

[0090] Experimental Example 3 Thermal Stability Characterization

[0091] The CsGa 1.3 P5O 16 :0.7Cr 3+ prepared in Example 3 of the present invention was subjected to a thermal stability test. The specific operation is as follows:

[0092] The phosphor CsGa 1.3 P5O 16 :0.7Cr 3+ of this Example 3 was placed on a temperature control platform, and the temperature was gradually increased. By using a temperature control heating platform in combination with an Ocean Optics QE pro spectrometer, the real-time spectral test results of the phosphor at different temperatures were obtained.

[0093] As Figure 10 shown, for the thermal stability test of CsGa 1.3 P5O 16 :0.7Cr 3+ prepared in Example 3 of the present invention, where the abscissa Wavelength is the wavelength and the ordinate Intensity is the PL intensity corresponding to the change in the external temperature. It can be Figure 10 seen that when the external temperature reaches 100 °C, the PL intensity can maintain 47% of the initial luminescence intensity, indicating that the phosphor has good thermal stability.

[0094] Experimental Example 4 Application Performance Characterization

[0095] The CsGa 1.3 P5O 16 :0.7Cr 3+Perform performance tests on the near-infrared LED device. The specific operations are as follows:

[0096] Mix the phosphor CsGa 1.3 P5O 16 :0.7Cr 3+ and epoxy resin in a mass ratio of 1:4, mix and stir to form a uniform colloid, and then dot the colloid on a 460 nm LED chip. After subsequent drying and encapsulation, a near-infrared LED device is obtained. Subsequently, use an Ocean Optics QE pro spectrometer to test the optical performance of the device, and use an MV-CA050-20GN type near-infrared camera to characterize the application performance of the device.

[0097] As Figure 11 shown, for the performance test of CsGa 1.3 P5O 16 :0.7Cr 3+ prepared in Example 3 of the present invention as a luminescent material for near-infrared LED devices, where the abscissa Wavelength is the wavelength and the ordinate Intensity is the PL intensity corresponding to the change in the applied current intensity. As Figure 11 can be seen, as the current intensity increases (from 30 mA to 300 mA), its peak shape does not change and the emission peak does not show saturation, indicating that the phosphor has good optical stability.

[0098] As Figure 12 shown, for the application performance test of CsGa 1.3 P5O 16 :0.7Cr 3+ prepared in Example 3 of the present invention in night vision imaging, where the left picture A is a photo of an item under a fluorescent lamp captured by a camera, and the right picture B is a photo captured by a near-infrared camera after turning on the near-infrared LED device in a dark environment. As Figure 12 can be seen, the near-infrared LED device has certain application prospects in the field of night vision imaging.

[0099] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description should not be considered as a limitation of the present invention. After those skilled in the art have read the above content, various modifications and substitutions to the present invention will be obvious. Therefore, the protection scope of the present invention should be defined by the appended claims.

Claims

1. A Cr 3+ activated near-infrared phosphor, characterized in that, The chemical formula of the near-infrared phosphor is CsGa 2- x P5O 16 :xCr 3+ , where 0.1 < x ≤ 1.

3.

2. The Cr 3+ activated near-infrared phosphor according to claim 1, characterized in that 0.3≤x≤1.3。 3. The Cr 3+ activated near-infrared phosphor according to claim 1, characterized in that, The chemical formula of the near-infrared phosphor is CsGa 1.7 P5O 16 :0.3Cr 3+ 、CsGa 1.5 P5O 16 :0.5Cr 3+ 、CsGa 1.3 P5O 16 :0.7Cr 3+ 、CsGa 1.1 P5O 16 :0.9Cr 3+ or CsGa 0.7 P5O 16 :1.3Cr 3+ .

4. The Cr 3+ activated near-infrared phosphor according to claim 1, characterized in that The excitation wavelength range of the near-infrared phosphor is 370~800 nm, and the emission wavelength range is 700~1100 nm.

5. The Cr according to any one of claims 1 to 4 3+ A method for preparing an activated near-infrared phosphor, characterized in that This method includes the following steps: (1) Grinding a cesium compound, a gallium compound, ammonium dihydrogen phosphate and a chromium compound to obtain a mixture; (2) Loading the mixture into a crucible and transferring it to a muffle furnace, heating it to 300~500 °C at a heating rate of 5 °C / min in an air atmosphere and holding for 2~5 h to obtain a pre-calcined massive precursor; (3) Grinding the cooled massive precursor, heating it to 700~900 °C at a heating rate of 5 °C / min in an air atmosphere in a muffle furnace and holding for 8~14 h to obtain the product after the first calcination reaction; (4) Continuing to take out the cooled product, grinding it into powder, heating it to 700~900 °C at a heating rate of 5 °C / min in an air atmosphere in a muffle furnace and holding for 8~14 h to obtain the product after the second calcination reaction; (5) Wait for the reaction to complete, and let the temperature cool naturally to room temperature. Post-treat the obtained product to obtain Cr 3+ Activate the near-infrared phosphor.

6. The preparation method according to claim 5, wherein, The cesium compound is selected from Cs2CO3, the gallium compound is selected from Ga2O3, and the chromium compound is selected from Cr2O3; Or / and, the post-treatment is successively carried out through crushing, grinding, washing with anhydrous ethanol, filtering, drying and grinding.

7. The Cr according to any one of claims 1 to 4 3+ Application of the activated near-infrared phosphor as a near-infrared light source.

8. The application according to claim 7, characterized in that, The Cr 3+ The excitation wavelength range of the activated near-infrared phosphor is 370~800 nm, which can match blue or red light-emitting diodes.

9. The application according to claim 8, characterized in that The near-infrared light source contains a near-infrared phosphor activated by Cr as described in any one of claims 1 to 3 3+ and a blue light-emitting diode with a luminous wavelength of 380 to 500 nm or a red light-emitting diode with a luminous wavelength of 620 to 700 nm, and is applied in the fields of night vision imaging and biological penetration imaging.

10. The application according to claim 7, characterized in that The Cr 3+ The emission wavelength range of the activated near-infrared phosphor is 700~1100 nm, covering the near-infrared I region.

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