Gallium germanate near-infrared luminescent material, preparation method and LED light-emitting device

Abstract

The invention discloses a gallium germanate near-infrared luminescent material, a preparation method and an LED light-emitting device. The general chemical formula of the luminescent material is Ca3Sn2Ga2GeO12: xFe < 3 + > (0lt; x is greater than or equal to 0.10), can be effectively excited by an ultraviolet or blue light band light source and emits high-intensity near-infrared light covering a range from far-infrared light to near-infrared light of 650-1000nm, and has very excellent light-emitting quantum efficiency (greater than 50%) and thermal stability (greater than 70% at 423K) compared with materials of the same type. The preparation method of the luminescent material is simple in process and environment-friendly, and the obtained product is pure in phase and stable in physicochemical property. The infrared LED light-emitting device formed by combining the light-emitting material and a commercial LED chip is excellent in light-emitting intensity, energy conversion efficiency and the like, and has wide application potential in the fields of near-infrared night vision, non-contact detection, food analysis, information anti-counterfeiting and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of luminescent materials, and in particular relates to a gallium germanate near-infrared luminescent material and a preparation method thereof, and an LED luminescent device. Background Art

[0002] In recent years, near-infrared light sources with good penetration, non-invasiveness, long service life, energy saving and environmental protection have been widely used in night vision, food analysis, non-destructive testing and biomedicine. In particular, with the increasing popularity of smart terminal devices such as smartphones, bracelets, and watches, higher and higher requirements are placed on small and portable near-infrared light sources. However, traditional solid-state light sources (such as halogen tungsten lamps) are difficult to meet the needs of portable near-infrared devices due to their shortcomings such as low luminous efficiency, high energy consumption and non-compact size. Therefore, near-infrared emitting fluorescent conversion LEDs (NIRpc-LEDs) have recently attracted widespread attention due to their small size, high efficiency and adjustable emission. However, the development of efficient broadband near-infrared emitting luminescent materials is one of the key obstacles encountered in the development of NIR pc-LEDs.

[0003] Currently reported broadband near-infrared emitting phosphors are mainly based on transition metal ions Cr 3+ , because when it is located in a weak octahedral coordinated crystal field, broadband emission can usually be generated in the range of 650-1200nm. In addition, due to the spin-allowed 4 A 2g → 4 T 1g It can effectively absorb blue light, which is a good match for commercial blue LED chips. 3+ The luminescence of is strongly dependent on the coordination environment of the matrix lattice, which requires a weak six-coordinated crystal field. 2 E g → 4 The narrowband emission from the A2 transition will dominate. In addition, Cr 3+ Under oxidative synthesis conditions, it is easy to react with Cr 4+ and Cr 6+ This not only limits the near-infrared luminescence efficiency of the material, but also increases the biological toxicity of the chromium-doped material, making it unsuitable for fields with high application safety requirements. 3+ Alternatives to activators can be used to accelerate the research progress and application of near-infrared luminescence. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the present invention provides a novel Fe 3+Activated gallium germanate near-infrared luminescent material with garnet structure, its preparation method and near-infrared LED prototype device. The luminescent material of the present invention has considerable absorption efficiency in the near-ultraviolet and visible blue light regions. In addition, compared with the same type of Fe 3+ activated luminescence system products, it can have excellent luminescence performance in a very wide doping concentration range. The broadband near-infrared light generated by it not only has a relatively high luminescence quantum efficiency but also has excellent luminescence thermal stability performance. At the same time, it can also be pumped by a low-cost blue LED chip, thereby providing an excellent alternative option other than Cr 3+ activated products. Specifically,

[0005] One of the purposes of the present invention is to provide a gallium germanate near-infrared luminescent material with garnet structure, and the chemical composition formula of the luminescent material is Ca3Sn2Ga2GeO 12 :xFe 3+ , where 0 < x ≤ 0.10. The luminescent material of the present invention uses gallium germanate with a garnet-type structure as the matrix and trivalent iron ions (Fe 3+ ) as the activator.

[0006] Another purpose of the present invention is to provide a preparation method of the above luminescent material, including the following steps:

[0007] 1) According to the stoichiometric ratio of the general formula Ca3Sn2Ga2GeO 12 :xFe 3+ (where 0 < x ≤ 0.10), accurately weigh the raw materials of calcium source, tin source, gallium source, germanium source and iron source by weight respectively, and mix them to obtain a raw material mixture; grind the raw material mixture to make it fully and evenly mixed;

[0008] 2) Calcinate the raw material mixture in step 1) in an air atmosphere to obtain a luminescent material. The calcination temperature is 1400 - 1500 °C and the time is 4 - 8 hours; the obtained luminescent material can be ground into powder form. Since the sintered body obtained by calcination usually has irregular sample particle morphology, relatively large particle size and uneven particle size distribution, it generally needs to be ground. The grinding time is generally 5 minutes to 2 hours, preferably 10 minutes to 1 hour, and more preferably 15 minutes to 30 minutes, and then a powder-shaped luminescent material with regular particle morphology, smaller particle size and uniform particle size distribution can be obtained.

[0009] Preferably, the sources of the raw materials described in step 1) are specifically as follows: the calcium source is one or more substances selected from the group consisting of simple calcium, calcium oxide, and compounds convertible into calcium oxide (for example, the calcium source is simple calcium, the calcium source is a mixture of simple calcium and calcium oxide, the calcium source is a mixture of two compounds convertible into calcium oxide, and the calcium source is a mixture of simple calcium and one compound convertible into calcium oxide); the tin source is tin oxide; the gallium source is gallium oxide; the germanium source is germanium oxide; and the iron source is iron oxide, ferroferric oxide, ferrous oxide, or ferric chloride.

[0010] Preferably, the compound convertible into calcium oxide includes chlorides, sulfides, carbonates, sulfates, phosphates and nitrates of calcium.

[0011] Preferably, the raw material mixture further contains a flux additive, and the flux additive is one or more of CaF2, NH4F, LiF, Li2CO3, Na2CO3, K2CO3 and H3BO3.

[0012] Preferably, the calcination in step 2) uses a heating device with a relatively high heating rate.

[0013] Preferably, the calcination in step 2) is performed by placing the raw material mixture in an alumina corundum crucible for calcination.

[0014] The third object of the present invention is to provide an infrared LED light-emitting device, which includes an LED chip and the light-emitting material described in claim 1, wherein the LED chip is an ultraviolet LED chip or a blue light LED chip, and the light-emitting material is located on the LED chip.

[0015] Preferably, the ultraviolet LED chip is an InGaN semiconductor chip with an emission wavelength in the range of 300-340 nm, and the blue light LED chip is an InGaN semiconductor chip with an emission wavelength in the range of 405-415 nm.

[0016] Preferably, the luminescent material is uniformly dispersed in epoxy resin, then covered on the LED chip by coating or dispensing, and cured by heating.

[0017] The luminescent material of the present invention is a kind of Fe 3+The activated new near-infrared luminescent material can be excited by ultraviolet band or visible blue light, and has a good application adaptability breadth. The preparation method of the luminescent material of the present invention is simple, easy to operate, has low raw material cost, has low requirements on production equipment and is pollution-free, and ultrafast synthesis of near-infrared luminescent materials. The obtained luminescent material has a wide excitation and emission range, and can emit high-intensity near-infrared light covering the range of far red to near infrared (650-1000nm), and has high luminescence quantum efficiency (>50%) and excellent luminescence thermal stability (>70%@423K). The luminescent material of the present invention has excellent luminescence performance and has great application potential in night vision, non-destructive testing, food analysis and information anti-counterfeiting, and the preparation method is simple and low-cost, which is expected to produce huge social and economic benefits and is suitable for promotion and industrial use. The NIR pc-LED prototype device formed by combining the luminescent material of the present invention with ultraviolet or blue light LED has good luminous intensity, lumen efficiency and photoelectric conversion efficiency, and can be used for high-power near-infrared luminescence applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 For the present invention, different Fe 3+ X-ray diffraction (XRD) pattern of near-infrared luminescent materials at activation concentrations;

[0019] Figure 2 is the excitation and emission spectra of the near-infrared luminescent material of the present invention;

[0020] Figure 3 The luminescence quantum efficiency test result of the near-infrared luminescent material of the present invention;

[0021] Figure 4 It is a graph showing the variation of the emission intensity of the near-infrared luminescent material of the present invention with temperature;

[0022] Figure 5 The luminous intensity of the near-infrared luminescent material prepared by introducing the Na2CO3 additive in the present invention is optimized and improved;

[0023] Figure 6 This is an electroluminescence spectrum diagram of the near-infrared LED light-emitting device of the present invention. DETAILED DESCRIPTION

[0024] The present invention will be described in detail below in conjunction with examples, which are merely illustrative and are not intended to limit the scope of application of the present invention. The present invention is not limited to the following embodiments or examples, and any modifications and variations that do not violate the spirit of the present invention should be included within the scope of the present invention.

[0025] Example 1: Ca3Sn2Ga2GeO 12 :xFe 3+(0 < x ≤ 0.10) Preparation of Luminescent Materials

[0026] According to the chemical formula Ca3Sn2Ga2GeO 12 :xFe 3+ , 0 < x ≤ 0.10 (in this example, x takes 0.002, 0.005, 0.01, 0.02, 0.03, 0.05, 0.07, 0.10 respectively to prepare the corresponding fluorescent materials: Ca3Sn2Ga2GeO 12 :0.002Fe 3+ 、Ca3Sn2Ga2GeO 12 :0.005Fe 3+ 、Ca3Sn2Ga2GeO 12 :0.01Fe 3+ 、Ca3Sn2Ga2GeO 12 :0.02Fe 3+ 、Ca3Sn2Ga2GeO 12 :0.03Fe 3+ 、Ca3Sn2Ga2GeO 12 :0.05Fe 3+ 、Ca3Sn2Ga2GeO 12 :0.07Fe 3+ 、Ca3Sn2Ga2GeO 12 :0.10Fe 3+ ), accurately weigh the powder raw materials CaCO3, SnO2, Ga2O3, GeO2, Fe2O3. Place the weighed raw materials in an agate mortar, grind until the raw materials are fully and evenly mixed, then transfer them to an alumina corundum crucible, place it in a high-temperature tube furnace, sinter rapidly at 1400 °C for 5 hours, take it out after natural cooling to room temperature, and grind again to obtain the 3+ near-infrared luminescent material activated by Fe. Detect the prepared luminescent material, and the results are as follows:

[0027] As Figure 1 shown in the X-ray diffraction (XRD) pattern, it shows that no impurity phase is generated in the prepared luminescent material, indicating that the phase is a single pure phase. The luminescent material prepared by the present invention has high luminescence brightness and has a wide excitation and emission range. For example, Figure 2 shown in the excitation and emission spectra of the Ca3Sn2Ga2GeO 12 :0.02Fe 3+ luminescent material, there are wide and strong excitations in the ultraviolet band (278 nm) and the blue light band (406 nm), and the best emission peak is located at ~756 nm, with a range of 650 - 1000 nm, indicating that it can match well with the InGaN semiconductor chip; Figure 3 is Ca3Sn2Ga2GeO12 :0.02Fe 3+ The photoluminescence quantum efficiency (PLQY) test results of the luminescent material showed that the PLQY measured under 278nm excitation can reach an excellent level of 54.1%; Figure 4 It is Ca3Sn2Ga2GeO 12 :0.02Fe 3+ The emission intensity of the luminescent material changes with temperature. It can be seen that at 423K, its emission intensity can still reach ~72% of the initial room temperature condition, showing that Fe 3+ The strong thermal stability of activated luminescence in the material of the present invention indicates that the near-infrared luminescent material of the present invention has certain prospects in high-power near-infrared applications.

[0028] Example 2: Adding cosolvent method and effect

[0029] According to the preparation method described in Example 1, after weighing each raw material according to the stoichiometric ratio of each element, one of CaF2, NH4F, LiF, Li2CO3, Na2CO3, K2CO3 or H3BO3 can be selected as a solubilizing additive to optimize the luminescence performance of the material, and the type of additive selected has a certain regulatory effect on the luminescence intensity of the final luminescent material. For example, weighing about 5wt% of the Na2CO3 additive to the total mass of the reference raw material mixture and grinding and mixing the mixture thoroughly can prepare the near-infrared luminescent material of the present invention under the same synthesis conditions as Example 1, such as Figure 5 The following is a diagram of the preparation of Ca3Sn2Ga2GeO 12 :0.02Fe 3+ Comparing the emission intensity of the samples with additional Na2CO3, it is obvious that the luminescence intensity of the samples with additional Na2CO3 has been further improved.

[0030] Example 5: Preparation of near-infrared LED light-emitting device

[0031] A near-infrared LED light-emitting device: using the near-infrared light-emitting material, packaging substrate and blue light InGaN semiconductor chip provided by the present invention. The near-infrared light-emitting material is a light-emitting material synthesized in the above-mentioned embodiment 1, and its chemical composition formula is Ca3Sn2Ga2GeO 12 :xFe 3+ (x = 0.02), i.e. Ca3Sn2Ga2GeO 12 :0.02Fe 3+The peak wavelength of the blue light InGaN semiconductor core is 410nm. The near-infrared luminescent material is uniformly dispersed in the epoxy resin, and covered on the InGaN chip by coating or dispensing. After high-temperature curing, the circuit is welded to obtain the near-infrared LED luminescent device of the present invention. The electroluminescent spectrum of the LED luminescent device is as follows Figure 6 As shown, blue light pumping of Ca3Sn2Ga2GeO 12 :0.02Fe 3+ Electroinduced near-infrared emission.

[0032] The conventional techniques and schemes not described in detail in the above embodiments are well known in the art, so they will not be described in detail here. The above embodiments and / or experimental examples describe the preferred embodiments of the present invention in detail, but the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, the technical scheme of the present invention can be subjected to a variety of simple modifications, and these simple modifications all belong to the protection scope of the present invention.

Claims

1. A garnet-structured gallium germanate near-infrared luminescent material, characterized in that: The chemical composition formula of the luminescent material is Ca3Sn2Ga2GeO 12 :xFe 3+ , where 0 <x≤0.10。 2. The method for preparing the luminescent material according to claim 1, characterized in that: The following steps are involved: 1) According to the general formula Ca3Sn2Ga2GeO 12 :xFe 3+ The raw materials of the calcium source, the tin source, the gallium source, the germanium source and the iron source are accurately weighed by weight according to the stoichiometric ratio, and mixed to obtain a raw material mixture; 2) calcining the raw material mixture in step 1) in an air atmosphere to obtain a luminescent material, wherein the calcination temperature is 1400-1500° C. and the time is 4-8 hours; the obtained luminescent material can be ground into powder.

3. The preparation method according to claim 2, characterized in that: The sources of the raw materials described in step 1) are specifically as follows: The calcium source is one or more substances selected from the group consisting of simple calcium, calcium oxide and compounds convertible into calcium oxide; the tin source is tin oxide; the gallium source is gallium oxide; the germanium source is germanium oxide; and the iron source is iron oxide, ferroferric oxide, ferrous oxide or ferric chloride.

4. The preparation method according to claim 3, characterized in that: The compounds convertible into calcium oxide include chlorides, sulfides, carbonates, sulfates, phosphates and nitrates of calcium.

5. The preparation method according to claim 2, characterized in that: The raw material mixture also contains flux additives, which are one or more of CaF2, NH4F, LiF, Li2CO3, Na2CO3, K2CO3 and H3BO3.

6. The preparation method according to claim 2, characterized in that: The calcination in step 2) is to place the raw material mixture in an alumina corundum crucible for calcination.

7. A near-infrared LED light-emitting device, characterized in that: It comprises an LED chip and the luminescent material according to claim 1, wherein the LED chip is an ultraviolet LED chip or a blue light LED chip, and the luminescent material covers the LED chip.

8. The light emitting device according to claim 7, characterized in that: The ultraviolet LED chip and the blue light LED chip are InGaN semiconductor chips with emission wavelengths in the range of 300-340nm and 405-415nm respectively.

9. The light emitting device according to claim 7 or 8, characterized in that: The luminescent material is uniformly dispersed in epoxy resin and then covered on the LED chip by coating or dispensing.

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