A gallate near-infrared phosphor based on spinel structure, its preparation method and application

Abstract

This invention belongs to the technical field of LED phosphors, and discloses a gallate near-infrared phosphor based on a spinel structure, its preparation method, and its application. The general chemical formula of the gallate near-infrared phosphor based on the spinel structure is: ZnAl x Ni y Ga (2‑x‑y) O4, where 0≤x≤0.05, 0≤y≤0.04; the preparation method involves thoroughly mixing and grinding the raw materials, then calcining them, and finally cooling them to room temperature before grinding to obtain gallium salt near-infrared phosphor. The preparation method of the gallium salt near-infrared phosphor of this invention uses common metal oxides as raw materials, resulting in phosphors with high luminous efficiency, stable chemical properties, and minimal brightness change at high temperatures. The preparation method is simple and easy to implement.

Description

Technical Field

[0001] This invention belongs to the field of LED phosphor technology, and relates to a gallate near-infrared phosphor based on spinel structure, its preparation method and application. Background Technology

[0002] Near-infrared (NIR) light, with its strong penetrating power, low thermal effect, and non-damaging properties, is widely used in night vision lighting, surveillance systems, iris recognition, infrared spectroscopy analysis, and bioimaging. In recent years, NIR fluorescent light-emitting diodes (NIR pc-LEDs) have gained widespread attention due to their advantages over traditional light sources, including smaller size, lower cost, and higher luminous efficiency. They are now widely used in food analysis, plant growth, night vision, and biomedical imaging, and are increasingly accepted by various companies, playing a crucial role in practical industrial and agricultural production. These applications urgently require near-infrared light sources with a wide emission band and high efficiency. Although traditional NIR light sources such as incandescent and halogen lamps can present a wide emission spectrum from visible to near-infrared, their low efficiency, short lifespan, large size, and high operating temperature hinder their practical application. Phosphors, as light conversion materials, are a key component of pc-LEDs, and different types of phosphor materials have been developed and applied in response to evolving needs. In recent years, Ni transition metal ions with wide near-infrared emission characteristics have become increasingly popular. 2+ Research on near-infrared fluorescent materials doped with inorganic compounds is quite active. This is because Ni 2+ of 3 The d-level is highly sensitive to its surrounding crystal field environment. Inorganic compounds with different coordination structures produce different crystal field intensities, resulting in Ni 2+ The peak wavelength and full width at half maximum (FWHM) of the emission spectrum vary. Although some near-infrared luminescent materials excited by blue light have been reported, they suffer from problems such as low luminescence intensity, narrow FWHM, and poor photothermal stability. Summary of the Invention

[0003] To address the problems existing in the background technology, the present invention provides a gallate near-infrared phosphor based on a spinel structure, its preparation method, and its application.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] A gallate near-infrared phosphor based on a spinel structure, wherein the general chemical formula of the gallate near-infrared phosphor is: ZnAl x Ni y Ga (2-x-y)O4, where 0 ≤ x ≤ 0.05, 0 ≤ y ≤ 0.04; the crystal structure of the matrix corresponding to the gallium salt near-infrared phosphor belongs to the cubic crystal system, with space group Fd. m; the excitation wavelength range is 380-650 nm, and the emission wavelength range is 1100-1650 nm.

[0006] Studies have shown that the properties of the matrix and the synergistic effect of doping elements have a significant impact on the performance of phosphors. The gallate near-infrared phosphor provided by this invention uses ZnGa₂O₄ as the matrix and is doped with Ni ions. 2+ To activate ions, Al was co-doped. 3 + By adjusting oxygen vacancy defects, the resulting gallate near-infrared fluorescent material can be effectively excited by near-ultraviolet, blue, or red light, producing fluorescence emission at 1290 nm with an internal quantum efficiency greater than 30%.

[0007] This invention also provides a method for preparing gallium salt near-infrared phosphors based on spinel structures, comprising the following steps:

[0008] Step 1: According to ZnAl x Ni y Ga (2-x-y) The chemical elemental stoichiometry of O4 is used to weigh Zn source, Al source, Ni source and Ga source as raw materials;

[0009] Step 2: Place all the raw materials from Step 1 into a clean agate mortar and grind them thoroughly to obtain a mixture;

[0010] Step 3: Calcine the mixture at high temperature;

[0011] Step 4: After calcination, grinding is performed to obtain the gallium salt near-infrared phosphor.

[0012] The preparation method provided by this invention is simple, easy to operate, has low equipment cost, and is pollution-free, making it suitable for widespread use.

[0013] Commonly used Zn, Al, Ni and Ga sources in this field can all be used in this invention.

[0014] Preferably, the Zn source is at least one of elemental Zn, oxides, chlorides, sulfides, or salts (e.g., carbonates, sulfates, phosphates, or nitrates). Examples include ZnO and ZnCO3.

[0015] Preferably, the Al source is at least one of elemental Al, oxides, chlorides, sulfides, or salts (e.g., carbonates, sulfates, phosphates, or nitrates). Examples include Al₂O₃ and Al(NO₃)₃.

[0016] Preferably, the Ni source is at least one of elemental Ni, oxide, hydroxide, sulfide, or salt (e.g., carbonate, sulfate, phosphate, or nitrate). Examples include NiO and Ni(OH)2.

[0017] Preferably, the Ga source is at least one of Ga oxides, chlorides, sulfides, or salts (e.g., carbonates, sulfates, phosphates, or nitrates). For example, Ga₂O₃.

[0018] Preferably, the mixing process in step 2 is as follows: grinding in a solvent (e.g., ethanol, water, methanol, etc.) until the solvent evaporates.

[0019] Preferably, the high-temperature calcination in step 3 is carried out at a temperature of 1000-1300 ℃ for 2-6 h.

[0020] Preferably, the high-temperature calcination in step 3 is carried out in an air atmosphere or an N2 atmosphere, and more preferably in an air atmosphere.

[0021] Preferably, the grinding time in step 4 is 5 min to 2 h, and more preferably 10 to 30 min.

[0022] Preferably, 0.01≤x≤0.04; 0.005≤y≤0.03.

[0023] More preferably, 0.01≤x≤0.03; 0.005≤y≤0.01.

[0024] Studies have shown that Al 3+ and Ni 2+ The doping amount has a certain influence on the synergistic effect of the two. When it is controlled within the above range, the intensity of the 380 nm violet light excitation peak and the corresponding 1290 nm near-infrared light emission peak are further enhanced, and the optimal value is reached when x=0.02 and y=0.008.

[0025] The present invention also claims protection for a near-infrared LED light-emitting device, comprising a packaging substrate, an LED chip, and the aforementioned gallate near-infrared phosphor disposed on the surface of the LED chip.

[0026] Preferably, the gallate near-infrared phosphor is coated on the surface of the LED chip.

[0027] Preferably, the LED chip is disposed on a packaging substrate.

[0028] Preferably, the LED chip is a violet LED chip.

[0029] Preferably, the LED chip is an InGaN semiconductor chip or a GaN semiconductor chip.

[0030] The preparation method of the above-mentioned near-infrared LED light-emitting device includes the following steps: mixing gallate near-infrared phosphor with adhesive, then coating it onto an LED chip fixed on a packaging substrate, and curing it to obtain the near-infrared LED light-emitting device.

[0031] Preferably, the adhesive is one or more of silicone, epoxy resin, and UV-curable adhesive.

[0032] More preferably, the adhesive is one or more of UV-curable adhesives or silicone.

[0033] The ratio of gallium salt near-infrared phosphor to adhesive is 1:3.

[0034] Technical principle of the invention:

[0035] This invention employs a cation-mediated valence state / field strength synergistic modulation strategy to add new defect energy levels to materials, which can capture some excited electrons. Furthermore, because the defect energy levels are related to Ni... 3 T2( 3 F) The energy levels are close, which can supplement the energy levels of F. 3 T2( 3 F) The energy level transitions to the nonradiative level. 3 A2( 3 The number of photons in F); in addition, Al 3+ The introduction of Ni supplements 2+ Replace Ga 3+ The charge imbalance caused by the location of the lattice site reduces the generation of oxygen vacancies, further reducing the capture of excited electrons by oxygen vacancies. This significantly increases the number of photons participating in nonradiative transitions, thereby greatly improving the luminescence intensity.

[0036] The original spinel-structured gallate near-infrared phosphor is ZnGa2O4:Ni 2+ Tests revealed that its luminescence intensity and quantum efficiency were low, with a luminescence center of 1290 nm and a full width at half maximum (FWHM) of 244 nm.

[0037] Compared with the prior art, the present invention has the following advantages:

[0038] (1) The near-infrared phosphor provided by this invention has high luminescence intensity, good temperature quenching characteristics, chemical stability, and a wide excitation and emission range. The excitation band covers the spectral region from 380 nm to 650 nm, the full width at half maximum (FWHM) is broadened from 244 nm to 254 nm, the emission intensity is increased by about 107%, the internal quantum yield is increased from 32.9% to 40.6%, and the external quantum yield is increased from 4.21% to 4.57%. The emission band covers the near-infrared region from 1100 nm to 1650 nm. This phosphor can be used as a light conversion material for blue LED chips to realize a broadband near-infrared light source.

[0039] (2) The phosphor emission band of the present invention is in the range of 1100-1650 nm, which can be applied not only to night vision monitoring, medical treatment, spectral detection and other fields, but also avoids the drawbacks of other infrared light acquisition methods. The light-emitting device of the present invention has high luminous efficiency, small size and low cost, and can be applied to various types of equipment. Attached Figure Description

[0040] Figure 1 A schematic diagram of phosphor structure and ion doping created in VESTA software;

[0041] Figure 2 The XRD patterns of the materials provided in Examples 1-5 and Comparative Examples 1 and 5 are compared with standard diffraction cards. The tests were conducted using a Rigaku MiniFlex 600 X-ray powder diffractometer.

[0042] Figure 3 Comparison of XRD images refined using MS software and schematic diagram of the material's crystal structure;

[0043] Figure 4 The excitation and emission spectra of the materials provided in Example 2 and Comparative Example 5 under 380 nm excitation are shown. The test was conducted using an Edinburgh FLS1000 steady-state transient fluorescence spectrometer with a 500W xenon lamp as the excitation source.

[0044] Figure 5 The emission spectra of the samples provided in Examples 1-5 and Comparative Examples 2-7 under 380 nm excitation are shown. The test was conducted using an Edinburgh FLS1000 steady-state transient fluorescence spectrometer with a 500W xenon lamp as the excitation source.

[0045] Figure 6 Near-infrared quantum efficiency test spectra of the samples provided in Comparative Example 5 and Example 2;

[0046] Figure 7 The graph shows the relationship between the near-infrared fluorescence peak intensity and the fluorescence peak integral intensity of the samples provided in Comparative Example 5 and Example 2 as a function of temperature. The fluorescence peak intensity and the fluorescence peak integral intensity are set to 1 when the temperature is 98K.

[0047] Figure 8 For Ni 2+ Coordinate potential energy diagram;

[0048] Figure 9 The images shown are of the LED device light source prepared in Example 6 under visible light (left) and near-infrared camera (right) driven by a 20mA current. The operating voltage and operating current of the LED chip excitation light source are set to 3.0V and 20mA, respectively.

[0049] Figure 10 The images shown are (a), (c), (b), and (d) near-infrared images of a human hand and a fruit, taken with a regular camera under the LED device light source prepared in Example 6. The near-infrared camera used was a SAP-0036SW-U3-H type near-infrared camera from Chongqing Gangyu High-Tech Development Co., Ltd.

[0050] Figure 11 The photoluminescence spectrum of the pc-LED device prepared in Example 6 was measured using a rapid spectrometer of Yuanfang Optoelectronics HAAS-2000, with a test wavelength range of 800-1600 nm.

[0051] Figure 12 This is a comparison chart of the power and photoelectric conversion efficiency of the pc-LED device prepared in Example 6. Detailed Implementation

[0052] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] Examples 1-4 provide a gallium salt near-infrared phosphor material, the preparation method of which is as follows: According to the above material composition design, the matrix is ​​ZnGa2O4, Ni... 2+ The doping amount is 0.8 mol%, and the doped ions Al in Examples 1-4 are... 3+ The doping amounts are 1 mol%, 2 mol%, 3 mol%, and 4 mol%, respectively. Zinc oxide (ZnO), nickel oxide (NiO), aluminum oxide (Al2O3), and gallium oxide (Ga2O3) are accurately weighed, and the above compound raw materials are weighed according to the stoichiometric ratio of each constituent element.

[0054] The above raw materials were placed in an agate mortar and ethanol was added and ground for 1 hour to ensure thorough mixing. The mixture was then transferred to a corundum crucible, covered, and placed in a high-temperature reaction furnace and calcined at 1000°C for 6 hours. After cooling to room temperature, the sample was removed and ground for 30 minutes to obtain the gallate near-infrared phosphors of Examples 1-4.

[0055] Example 5 provides a gallium salt near-infrared phosphor material, the preparation method of which is as follows: According to the above material composition design, the matrix is ​​ZnGa2O4, Ni... 2+ The doping amount is 0.8 mol%, and the doped ions Al in Example 5 are... 3+The doping amount is 5 mol%. Zinc oxide (ZnO), nickel oxide (NiO), aluminum oxide (Al2O3) and gallium oxide (Ga2O3) are accurately weighed and weighed according to the stoichiometric ratio of each constituent element.

[0056] The above raw materials were placed in an agate mortar and ethanol was added and ground for 1 hour to ensure thorough mixing. The mixture was then transferred to a corundum crucible, covered, and placed in a high-temperature reaction furnace and calcined at 1300°C for 2 hours. After cooling to room temperature, the sample was removed and ground for 10 minutes to obtain the gallate near-infrared phosphor of Example 5.

[0057] Example 6

[0058] This embodiment provides a near-infrared LED light-emitting device.

[0059] The near-infrared LED light-emitting device is prepared according to the following method: It includes a packaging substrate, an LED chip, and a phosphor capable of effectively absorbing the light emitted by the LED chip and emitting near-infrared light. The near-infrared phosphor is the near-red phosphor of Example 2 above, with the chemical formula ZnGa2O4:0.8%Ni / 2%Al. The LED chip is a violet semiconductor chip with a peak emission wavelength of 370-380nm. The near-infrared phosphor is uniformly dispersed in AB glue (the mass ratio of near-infrared phosphor to AB glue is 1:3), and coated onto the chip (the chip is fixed on the packaging substrate). The circuit is then connected to obtain the near-infrared LED light-emitting device of the present invention.

[0060] Based on Example 6, the effect of different grinding times on product performance was investigated. The process was basically the same as in Example 6, except that the grinding time for sample removal was changed. The results are shown in the table below:

[0061]

[0062] As can be seen from the table above: if the grinding time is <10 min (e.g., 5 min), the raw materials are not mixed evenly, resulting in local impurity phases in the calcined product, the emission intensity drops to 25.3%, and the internal quantum efficiency is below 30%; if the grinding time is >30 min (e.g., 60 min), the particles are excessively fined, the specific surface area increases, and it is easy to adsorb moisture and impurities in the air, resulting in an increase in non-radiative transitions during the luminescence process, and the internal quantum efficiency drops to 28.1%; only when the grinding time is 10-30 min, the product is evenly mixed and the particle size is moderate, and the emission intensity and quantum efficiency are both optimal. At the same time, this application demonstrates through experiments that a longer grinding time is not necessarily better.

[0063] Comparative Examples 1-7

[0064] This comparative example provides several different Ni 2+ Al3+ Gallate near-infrared phosphor material with varying doping concentration, namely ZnGa2O4:x%Ni,y%Al 3+ The preparation method is as follows: Based on the above material composition design, the matrix is ​​ZnGa2O4, wherein Comparative Example 1 contains Ni doping ions. 2+ And Al 3+ The doping amount of all samples was 0 mol%; Comparative Example 2: Ni-doped ions 2+ And Al 3+ The doping amounts were 0.8 mol% and 0 mol%, respectively; Comparative Examples 3-7: Ni-doped ions 2+ All were 0.8 mol%, with Al doping ions. 3+ The doping amounts are 1 mol%, 2 mol%, 3 mol%, 4 mol%, and 5 mol%, respectively. Gallium oxide (Ga2O3), magnesium oxide (ZnO), and nickel oxide (NiO) are accurately weighed, and the above compound raw materials are weighed according to the stoichiometric ratio of each constituent element.

[0065] The above raw materials were placed in an agate mortar and ethanol was added and ground for 1 hour to ensure thorough mixing. The mixture was then transferred to a corundum crucible, covered, and placed in a high-temperature reaction furnace at 1300°C for 6 hours. After cooling to room temperature, the samples were removed and ground for 10 minutes to obtain gallium salt near-infrared phosphors (Comparative Examples 1-7).

[0066] Performance testing was conducted on the Ni provided in each embodiment and comparative example. 2+ The performance of the doped gallium salt near-infrared phosphor and the corresponding near-infrared LED light-emitting device was measured.

[0067] Figure 1 The schematic diagram of the phosphor structure is shown, which exhibits obvious cubic crystal system characteristics, belonging to the spinel structure, and Al 3+ Prioritize occupying Zn 2+ Site, Ni 2+ Occupy Ga 3+ It has a site and does not generate oxygen vacancies.

[0068] Figure 2 X-ray diffraction analysis showed that all samples exhibited a pure-phase spinel structure (JCPDS38-1240), with sharp and high-intensity diffraction peaks, indicating good crystallinity of the material.

[0069] Figure 3 Its reliability factor (R) was refined using the MS software Rietveld. wp， R p All values ​​were less than 10.00%, which is within an acceptable range, confirming that the sample is a single phase.

[0070] Depend on Figure 4It can be seen that, under 380 nm excitation, when monitoring near-infrared light emission at 1290 nm, all doped samples can emit near-infrared light centered at 1290 nm, exhibiting similar excitation peak shapes. The excitation band covers the spectral region from 380 nm to 650 nm, and the emission band covers the near-infrared region from 1100 nm to 1650 nm. Furthermore, Al... 3+ / Ni 2+ The emission peak of the co-doped sample is significantly enhanced. Spectral characteristics show that the 380 nm peak is due to Ni. 2+ of 3 A2( 3 F)→ 3 T1( 3 P) transition; a weak peak exists at 622 nm. 3 A2( 3 F) → 3 T1( 3 F) Leap.

[0071] Depend on Figure 5 It can be seen that, under 380 nm excitation, the samples of each embodiment and comparative example exhibit similar emission peak shapes, while there are differences in relative intensity. Among the comparative examples, Comparative Example 5 has the highest emission intensity, while Example 2 in the embodiments has the highest emission intensity.

[0072] Figure 6 With an excitation wavelength of 380 nm, the internal quantum efficiencies were 32.9% and 40.6%, respectively, while the external quantum yield increased from 4.21% to 4.57%; that is, Al doping... 3+ The post-quantum yield is significantly improved.

[0073] Depend on Figure 7 It can be seen that all embodiments and comparative examples have strong thermal stability at low temperatures of 98K-245K, and the comparative example even has a certain degree of reverse thermal quenching performance.

[0074] Figure 8 For Ni 2+ The potential energy diagram shows that, under 380 nm ultraviolet light excitation, some electrons emerge from the ground state of nickel ions. 3 A2( 3 F) Excited to nickel ions 3 T1( 3 The energy level of P). Then, the excited electrons transition from the P level via nonradiative transitions. 3 T1( 3 P) Return to 3 T2( 3 During the F) energy level process, some of the excited electrons are captured by the formed oxygen vacancies, which is not conducive to further nonradiative transitions, while the other part transitions nonradiatively to the doped Al. 3+ The defect energy level E that forms between the valence band and conduction band afterwards TDue to the defect energy level E T and 3 T2( 3 F) The energy levels are relatively close, allowing excited electrons to originate from the defect energy level E. T Transfer to 3 T2( 3 F), and from 3 T2( 3 F) Jump to 3 A2( 3 The process of F) contributes to near-infrared (NIR) radiation, therefore, by doping Al... 3+ Reducing the generation of oxygen vacancies and introducing new defect energy levels can significantly improve the near-infrared luminescence performance of materials.

[0075] Depend on Figure 9 It can be seen that this LED can emit near-infrared light and can be used as a near-infrared light alternative light source.

[0076] Figure 10 The comparison between near-infrared photographs of a human hand taken under the LED device light source prepared in Example 6 and photographs of a human hand taken under a regular camera reveals that the NIR light from the device allows us to observe the details of blood vessels deep within the tissue, proving that this material can be used in medical imaging and non-destructive testing of fruits.

[0077] Figure 11 The photoluminescence spectrum of the pc-LED device prepared in Example 6 is obtained from... Figure 11 It can be seen that the greater the current, the higher the luminous intensity.

[0078] Depend on Figure 12 It can be seen that the output power of the device is directly proportional to the input current, while the photoelectric conversion efficiency has a certain inverse proportional function relationship with the current.

[0079] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a gallate near-infrared fluorescent powder based on a spinel structure, characterized in that, The method comprises the following steps: Step 1: ZnAl x Ni y Ga (2-x-y) The stoichiometric ratio of the chemical elements of ZnAl O4 is weighed as raw materials. Step 2: Put the raw materials in step 1 into a marble mortar and mix and grind them thoroughly to obtain a mixture; Step 3: Perform calcination treatment on the mixture; Step 4: Grind the calcined mixture to obtain a gallate near-infrared fluorescent powder based on a spinel structure; The calcination temperature in step 3 is 1000-1300℃, and the time is 2-6h; The grinding time in step 4 is 10-30min; The chemical general formula of the spinel structure-based gallate near-infrared fluorescent powder is: ZnAl x Ni y Ga (2-x-y) O4, wherein 0 x ≤0.05, 0 y ≤0.04; the crystal structure of the spinel structure-based gallate near-infrared fluorescent powder corresponds to a cubic system, and the space group is Fd m; the excitation wavelength range is 380-650 nm, the emission wavelength range is 1100-1650 nm, and the internal quantum efficiency is greater than 30%.

2. The method for preparing gallate near-infrared fluorescent powder based on spinel structure according to claim 1, characterized in that, The mixing process in step 2 is: grinding in a solvent until the solvent volatilizes.

3. The method for preparing gallate near-infrared phosphor based on spinel structure according to claim 1, characterized in that, The calcination in step 3 is performed in an air atmosphere or a N2 atmosphere.

4. A gallate near-infrared fluorescent powder based on a spinel structure prepared by the method according to any one of claims 1-3.

5. Use of the gallate fluoride near-infrared fluorescent powder based on the spinel structure according to claim 4, characterized in that, The gallate near-infrared fluorescent powder based on a spinel structure is applied to the preparation of a near-infrared LED light-emitting device, and the device comprises an encapsulation substrate, an LED chip and the gallate near-infrared fluorescent powder based on a spinel structure arranged on the surface of the LED chip, and the LED chip is arranged on the encapsulation substrate.

6. The use of the gallate phosphor based on the spinel structure according to claim 5, characterized in that, The LED chip is a violet LED chip, an InGaN semiconductor chip or a GaN semiconductor chip.

7. The use of the gallate fluorescent powder based on spinel structure according to claim 5, characterized in that, The preparation method of the near-infrared LED light-emitting device comprises the following steps: mixing the gallate near-infrared fluorescent powder based on a spinel structure with glue, then coating the mixture on the LED chip fixed on the encapsulation substrate, and after solidification, the near-infrared LED light-emitting device is obtained.

8. The use of the gallate phosphor based on the spinel structure according to claim 7, characterized in that, The glue is one or more of silicone, epoxy resin and ultraviolet curing glue, and the mixing ratio of the gallate near-infrared fluorescent powder based on a spinel structure to the glue is 1:3.

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