Fluorescent powder based on negative thermal expansion material and preparation method and application thereof

Abstract

The invention relates to the technical field of fluorescent material preparation, in particular to fluorescent powder based on a negative thermal expansion material and a preparation method and application thereof. The fluorescent powder comprises an Sc2Mo3O12 matrix and Tm < 3 + > / Dy < 3 + > doped ions, and is prepared by a high-temperature solid-phase method. The fluorescent powder can obtain white light emission of color-adjustable coordinates by adjusting the concentration of Tm < 3 + > / Dy < 3 + > under excitation of the wavelength of 354 nm. When the concentration of Dy < 3 + > is 4%, the chromaticity coordinate of the fluorescent powder is (0.3311, 0.2877) close to ideal white light, the fluorescent powder shows good light-emitting stability in a wide temperature range of 298K to 573K, the light-emitting intensity at the high temperature of 573K can still keep 60% of the initial intensity at the room temperature, and the fluorescent powder can be widely applied to high-power and high-temperature environment white light LED illumination in the fields of precise instruments, aerospace and the like.

Description

Technical Field

[0001] This invention relates to the field of fluorescent material preparation technology, specifically to a phosphor based on a negative thermal expansion material, its preparation method, and its application. Background Technology

[0002] In the field of modern lighting and display technology, light-emitting diodes (LEDs) are widely used in everyday lighting, display devices, automotive headlights, and high-power outdoor lighting due to their advantages such as high efficiency, energy saving, and long lifespan. White light-emitting diodes (WLEDs), as the core application form of LEDs in the lighting field, are currently manufactured using two main methods: one is blue light-emitting diodes based on hybrid GaN chips and the other is Y3Al5O4. 12 One approach involves using yellow light emitted from Ce(YAG:Ce) phosphors. YAG:Ce phosphors can be effectively excited by 460nm blue light, and white light emission can be achieved by combining them with a blue LED chip. Another approach uses ultraviolet / near-ultraviolet LEDs as excitation sources to drive the mixing of red, green, and blue phosphors to emit white light. However, existing technologies still have problems, such as high device cost, poor stability, and limited luminous efficiency. Among these, the thermal quenching effect of fluorescent materials is particularly prominent.

[0003] For fluorescent materials, the emission intensity changes with the external environment. The most common phenomenon is that the emission intensity of fluorescent materials gradually decreases as the temperature rises, which is known as the "thermal quenching effect." This effect seriously affects the performance of WLED devices and hinders their expansion into high-power lighting applications.

[0004] To address this issue, researchers have proposed several solutions. For example, Xia et al. (Puzhen Xia, Bin Xie, Xiaobing Luo. Enhancing Heat Dissipation of Photoluminescent Composite in White-Light-Emitting Diodes by 3D-Interconnected Thermal Conducting Pathways. Micromachines, 2022, 13: 1222.) used a simplified bubble template method to construct three-dimensional interconnected thermal conduction paths composed of hexagonal boron nitride sheets in photoluminescent composite materials. Zhang et al. (Qinggang Zhang, Mengda He, QunWan, et al. Suppressing thermal quenching of lead halide perovskitenanocrystals by constructing a widebandgap surface layer for achieving thermally stable white light-emitting diodes. Chemical Science, 2022, 13:3719-3727.) used an anionic passivation strategy to transform the lead on the surface of CsPbBr3 nanocrystals into a thermally stable passivation layer, suppressing hot quenching and improving the structural thermal stability. Chen et al. (Songmao Chen, Caiman Yan, Yong Tang, et al. Improvement in Luminous Efficacy and Thermal Performance Using Quantum Dots Spherical Shell for White Light Emitting Diodes. Nanomaterials, 2018, 8:618.) designed spherical shell QDs thin film structures for COB-WLEDs to enhance luminous efficiency and heat dissipation. However, these methods still have limitations in high-power LED applications: high thermal conductivity matrices may introduce compatibility issues, doped ions may affect the purity of emitted color, and the fabrication process of spherical shell structures is complex and costly. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a phosphor based on a negative thermal expansion material, its preparation method, and its applications. The chemical formula is Sc₂Mo₃O₃. 12 xTm3+ yDy 3+ The phosphor includes Sc2Mo3O 12 matrix and Tm 3+ / Dy 3+ Doped ions. Sc2Mo3O 12 At high temperatures, the lattice contraction caused by the tetrahedral rotation of MoO4 in the matrix not only enhances Tm 3+ and Dy 3+ The energy transfer between them significantly suppresses heat dissipation, thereby weakening the thermal quenching effect and maintaining the luminescence performance of fluorescent materials at high temperatures; moreover, it enhances the structural stability of the material and reduces structural deformation and damage caused by thermal expansion.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: The first objective of this invention is to provide a phosphor based on a negative thermal expansion material, wherein the phosphor is Sc2Mo3O 12 Matrix, co-doped Tm 3+ and Dy 3+ Ion formation; the chemical formula of the phosphor is Sc2Mo3O. 12 xTm 3+ yDy 3+ Among them, Tm 3+ With a matrix doping concentration x of 5 at.%, Dy 3+ The doping amount y in the matrix is ​​1 at.% to 5 at.%.

[0007] In a preferred embodiment of the present invention, y is 4at.%.

[0008] In a preferred embodiment of the present invention, the chromaticity coordinates of the phosphor are (0.3311, 0.2877), and the color temperature is 3010K.

[0009] A second objective of this invention is to provide a method for preparing the above-mentioned phosphor based on a negative thermal expansion material, comprising the following steps: Sc₂O₃, MoO₃, Tm₂O₃, and Dy₂O₃ were weighed according to stoichiometric ratios and mixed to obtain a mixture; the mixture was then calcined to form Tm₂O₃. 3+ / Dy 3+ Co-doped Sc2Mo3O 12 The structure was obtained to produce a phosphor based on a negative thermal expansion material.

[0010] In a preferred embodiment of the present invention, calcination refers to first heating to 480℃~520℃ and holding at that temperature for 5.5h~6.5h, then heating to 880℃~920℃ and holding at that temperature for another 3.5h~4.5h.

[0011] In a preferred embodiment of the present invention, the heating rate during calcination is 3°C / min to 10°C / min.

[0012] In a preferred embodiment of the present invention, the mixture is ground after mixing to obtain a mixture. Anhydrous ethanol needs to be added before grinding, and the volume ratio of anhydrous ethanol to the mixture is 1:1.

[0013] A third objective of this invention is to provide an application of the aforementioned phosphor based on a negative thermal expansion material in a white light-emitting diode.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention provides a phosphor based on a negative thermal expansion material, with the chemical formula Sc2Mo3O. 12 xTm 3+ yDy 3+ The phosphor includes Sc2Mo3O 12 matrix and Tm 3+ / Dy 3+ Doped ions. Among them, Sc2Mo3O 12 As a negative thermal expansion material, the matrix undergoes lattice contraction at high temperatures due to the rotation of internal MoO4 tetrahedra, which not only reduces the distance between ions but also enhances Tm. 3+ and Dy 3+ The energy transfer efficiency between the phosphors is significantly improved, heat dissipation is significantly suppressed, thereby reducing the thermal quenching effect and maintaining the luminescence performance of the fluorescent material at high temperatures. Furthermore, it enhances the structural stability of the material, reducing structural deformation and damage caused by thermal expansion. The phosphor based on a negative thermal expansion material with good thermal stability, as described in this invention, has significant application potential in LED applications in fields such as precision instruments, microelectronic packaging, and aerospace.

[0015] 2. This invention provides a method for preparing phosphors based on negative thermal expansion materials, specifically Sc2Mo3O prepared via a high-temperature solid-state method. 12 A negative thermal expansion material was developed, and tunable white light emission with adjustable color coordinates was achieved by adjusting the Dy / Tm ion concentration under 354nm wavelength excitation. When Dy... 3+ At a concentration of 4%, the phosphor retains 60% of its luminescence intensity at 200°C. Calculations show that the activation energy at 347nm excitation is Ea = 0.2083 eV, higher than that of other phosphors. The CIE chromaticity coordinates are (0.3311, 0.2877), close to the standard white light coordinates (0.33, 0.33), with a color temperature of 3010K. This phosphor, exhibiting excellent thermal stability, is a promising candidate material for high-temperature ambient lighting. This invention's phosphor, based on a negative thermal expansion material and possessing excellent thermal stability, has significant application potential in LED applications in precision instruments, microelectronic packaging, and aerospace. Attached Figure Description

[0016] Figure 1 The images show the XRD patterns of the phosphors used in Examples 1 to 5 and Comparative Examples 1 to 6 of this invention. Figure 1 Figure (a) shows the phosphors of Comparative Examples 1 to 6, and Figure (b) shows the XRD patterns of the phosphors of Examples 1 to 5.

[0017] Figure 2 This is a SEM image of the phosphor prepared in Example 1 of the present invention. Figure 2 Figure (a) is a SEM image at 2 μm, and Figure (b) is a SEM image at 20 μm.

[0018] Figure 3 This is an elemental distribution diagram of the phosphor prepared in Example 1 of the present invention. Figure 3 Figure (a) shows the distribution of Dy element, Figure (b) shows the distribution of Tm element, Figure (c) shows the distribution of Sc element, Figure (d) shows the distribution of Mo element, and Figure (e) shows the distribution of O element.

[0019] Figure 4 The images show the spectra of the phosphors of Comparative Examples 1 to 6 of this invention under 354 nm ultraviolet light excitation.

[0020] Figure 5 The images show the spectra of the phosphors in Examples 1 to 5 of this invention under 354 nm ultraviolet light excitation.

[0021] Figure 6 The Sc2Mo3O of the present invention 12 5%Tm 3+ yDy 3+ A schematic diagram of the energy transfer process.

[0022] Figure 7 The images show the lifetime of the phosphors used in Examples 1 to 5 and Comparative Example 3 of this invention.

[0023] Figure 8 Sc2Mo3O is the Sc2Mo3O of Embodiment 1 of the present invention. 12 5%Tm 3+ 4%Dy 3+ Temperature-dependent spectra of phosphors excited at 354 nm.

[0024] Figure 9 Sc2Mo3O is the Sc2Mo3O of Embodiment 1 of the present invention. 12 5%Tm 3+ 4%Dy 3+ Activation energy diagram of phosphor.

[0025] Figure 10 The present invention is Sc2Mo3O 125%Tm 3+ y%Dy 3+ CIE diagram of phosphor. Detailed Implementation

[0026] 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.

[0027] It should be noted that the technical terms used in this invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.

[0028] Existing fluorescent materials, due to their thermal quenching effect, hinder their application in high-power lighting. Although researchers have proposed various improvement schemes, they still have limitations in high-power LED applications: high thermal conductivity matrices may introduce compatibility issues, doped ions may affect the purity of emitted colors, and the fabrication process of spherical shell structures is complex and costly. Based on this, this invention utilizes Sc2Mo3O 12 A series of co-doped Tm were synthesized in the matrix. 3+ / Dy 3+ This ion-based phosphor exhibits lattice distortion and shrinkage under elevated temperatures, significantly enhancing energy transfer efficiency between ions and achieving excellent thermal stability. Experimental results show that the material retains 60% of its initial emission intensity at 573 K, while stably emitting high-quality white light with CIE color coordinates (0.331, 0.288), demonstrating promising application prospects.

[0029] First, this invention provides a phosphor based on a negative thermal expansion material, wherein the phosphor is Sc2Mo3O 12 Matrix, co-doped Tm 3+ and Dy 3+ Ion formation; the chemical formula of the phosphor is Sc2Mo3O. 12 xTm 3+ yDy 3+ Among them, Tm 3+ With a matrix doping concentration x of 5 at.%, Dy 3+ The doping amount y in the matrix is ​​1 at.% to 5 at.%.

[0030] The value of y is 4at.%.

[0031] The phosphor has chromaticity coordinates of (0.3311, 0.2877) and a color temperature of 3010K.

[0032] It should be noted that Sc2Mo3O is used in this invention. 12 As a material with negative thermal expansion, it undergoes lattice contraction at high temperatures due to the rotation of the internal MoO4 tetrahedra. This contraction not only reduces the distance between ions but also enhances Tm. 3+ and Dy 3+ This improves energy transfer efficiency and significantly suppresses heat dissipation, thereby mitigating the thermal quenching effect and maintaining the material's luminescence properties at high temperatures. Furthermore, this lattice contraction enhances the material's structural stability, reducing structural deformation and damage caused by thermal expansion.

[0033] Secondly, this invention provides a method for preparing the above-mentioned phosphor based on a negative thermal expansion material, characterized by comprising the following steps: S1. Weigh Sc2O3, MoO3, Tm2O3 and Dy2O3 according to the stoichiometric ratio and mix them to obtain a mixture.

[0034] S2. Calcine the mixture to form Tm 3+ / Dy 3+ Co-doped Sc2Mo3O 12 The structure was obtained to produce a phosphor based on a negative thermal expansion material.

[0035] It should be noted that during the calcination process of this invention, the doping amount of Tm is a%, and the doping amount of Dy is b%, and the chemical reaction equation is as follows: Sc2O3 + MoO3 + Tm2O3 + Dy2O3 → Sc 2-(a%+b%) Tm a% Dy b% Mo3O 12 .

[0036] The calcination refers to first heating to 480℃~520℃ and holding at that temperature for 5.5h~6.5h to activate the reactants, and then heating to 880℃~920℃ and holding at that temperature for another 3.5h~4.5h to allow the reactants to react fully.

[0037] During the calcination process, the heating rate is 3℃ / min to 10℃ / min.

[0038] After the calcination is completed, the sample needs to be allowed to cool naturally to room temperature, and then ground into powder again to obtain phosphor based on negative thermal expansion material.

[0039] The mixture is then ground to obtain a final mixture. Anhydrous ethanol is added before grinding, with a volume ratio of anhydrous ethanol to the mixture of 1:1. The purpose of grinding is to ensure that all raw materials are thoroughly and evenly mixed.

[0040] Finally, this invention provides an application of the above-mentioned phosphor based on negative thermal expansion material in white light-emitting diodes.

[0041] This invention prepares a series of Sc2Mo3O products via a high-temperature solid-state method. 12 A negative thermal expansion material was developed, and tunable white light emission with adjustable color coordinates was achieved by adjusting the Dy / Tm ion concentration under 354nm wavelength excitation. When Dy... 3+ At a concentration of 4%, the phosphor retains 60% of its luminescence intensity at 200℃. Calculations show that the activation energy at 347nm excitation is Ea = 0.2083 eV, higher than that of other phosphors. The CIE chromaticity coordinates are (0.3311, 0.2877), close to the standard white light coordinates (0.33, 0.33), with a color temperature of 3010K. This phosphor, exhibiting good thermal stability, shows promise as a candidate material for high-temperature ambient lighting.

[0042] The following specific examples will provide further explanation.

[0043] Example 1 A phosphor based on a negative thermal expansion material, with the chemical formula Sc2Mo3O 12 0.05Tm 3+ 0.04Dy 3+ .

[0044] The above-mentioned method for preparing phosphors based on negative thermal expansion materials includes the following steps: S1. Weigh out the corresponding amounts of Sc2O3, MoO3, Tm2O3 and Dy2O3 according to the stoichiometric ratio.

[0045] S2. Place all the raw materials from S1 into a mortar, add 2 mL of anhydrous ethanol, and grind until they are mixed evenly to obtain a mixture.

[0046] S3. Place the mixture in a muffle furnace for high-temperature calcination. First, raise the temperature to 500°C at a rate of 5°C / min and hold for 6 hours; then raise the temperature to 900°C at a rate of 5°C / min and hold for another 4 hours.

[0047] S4. After calcination, allow the sample to cool naturally to room temperature, and then grind the sample into powder again to obtain a phosphor based on a negative thermal expansion material, i.e., doped with 5% Tm. 3+ and 4% Dy 3+ Sc2Mo3O 12 Phosphor based.

[0048] Example 2 A phosphor based on a negative thermal expansion material, with the chemical formula Sc2Mo3O 12 0.05Tm 3+ 0.01Dy 3+ .

[0049] The above-mentioned method for preparing phosphors based on negative thermal expansion materials includes the following steps: S1. Weigh out the corresponding amounts of Sc2O3, MoO3, Tm2O3 and Dy2O3 according to the stoichiometric ratio.

[0050] S2. Place all the raw materials from S1 into a mortar, add 2 mL of anhydrous ethanol, and grind until they are mixed evenly to obtain a mixture.

[0051] S3. Place the mixture in a muffle furnace for high-temperature calcination. First, raise the temperature to 500°C at a rate of 5°C / min and hold for 6 hours; then raise the temperature to 900°C at a rate of 5°C / min and hold for another 4 hours.

[0052] S4. After calcination, allow the sample to cool naturally to room temperature, and then grind the sample into powder again to obtain a phosphor based on a negative thermal expansion material, i.e., doped with 5% Tm. 3+ and 1%Dy 3+ Sc2Mo3O 12 Phosphor based.

[0053] Example 3 A phosphor based on a negative thermal expansion material, with the chemical formula Sc2Mo3O 12 0.05Tm 3+ 0.02Dy 3+ .

[0054] The above-mentioned method for preparing phosphors based on negative thermal expansion materials includes the following steps: S1. Weigh out the corresponding amounts of Sc2O3, MoO3, Tm2O3 and Dy2O3 according to the stoichiometric ratio.

[0055] S2. Place all the raw materials from S1 into a mortar, add 2 mL of anhydrous ethanol, and grind until they are mixed evenly to obtain a mixture.

[0056] S3. Place the mixture in a muffle furnace for high-temperature calcination. First, raise the temperature to 500°C at a rate of 5°C / min and hold for 6 hours; then raise the temperature to 900°C at a rate of 5°C / min and hold for another 4 hours.

[0057] S4. After calcination, allow the sample to cool naturally to room temperature, and then grind the sample into powder again to obtain a phosphor based on a negative thermal expansion material, i.e., doped with 5% Tm. 3+ and 2%Dy 3+ Sc2Mo3O 12 Phosphor based.

[0058] Example 4 A phosphor based on a negative thermal expansion material, with the chemical formula Sc2Mo3O 12 0.05Tm 3+ 0.03Dy 3+ .

[0059] The above-mentioned method for preparing phosphors based on negative thermal expansion materials includes the following steps: S1. Weigh out the corresponding amounts of Sc2O3, MoO3, Tm2O3 and Dy2O3 according to the stoichiometric ratio.

[0060] S2. Place all the raw materials from S1 into a mortar, add 2 mL of anhydrous ethanol, and grind until they are mixed evenly to obtain a mixture.

[0061] S3. Place the mixture in a muffle furnace for high-temperature calcination. First, raise the temperature to 500°C at a rate of 5°C / min and hold for 6 hours; then raise the temperature to 900°C at a rate of 5°C / min and hold for another 4 hours.

[0062] S4. After calcination, allow the sample to cool naturally to room temperature, and then grind the sample into powder again to obtain a phosphor based on a negative thermal expansion material, i.e., doped with 5% Tm. 3+ and 3%Dy 3+ Sc2Mo3O 12 Phosphor based.

[0063] Example 5 A phosphor based on a negative thermal expansion material, with the chemical formula Sc2Mo3O 12 0.05Tm 3+ 0.05Dy 3+ .

[0064] The above-mentioned method for preparing phosphors based on negative thermal expansion materials includes the following steps: S1. Weigh out the corresponding amounts of Sc2O3, MoO3, Tm2O3 and Dy2O3 according to the stoichiometric ratio.

[0065] S2. Place all the raw materials from S1 into a mortar, add 2 mL of anhydrous ethanol, and grind until they are mixed evenly to obtain a mixture.

[0066] S3. Place the mixture in a muffle furnace for high-temperature calcination. First, raise the temperature to 500°C at a rate of 5°C / min and hold for 6 hours; then raise the temperature to 900°C at a rate of 5°C / min and hold for another 4 hours.

[0067] S4. After calcination, allow the sample to cool naturally to room temperature, and then grind the sample into powder again to obtain a phosphor based on a negative thermal expansion material, i.e., doped with 5% Tm. 3+ and 5% Dy 3+ Sc2Mo3O 12 Phosphor based.

[0068] Comparative Example 1 A phosphor based on a negative thermal expansion material, with the chemical formula Sc2Mo3O 12 : 0Tm 3+ .

[0069] The above-mentioned method for preparing phosphors based on negative thermal expansion materials includes the following steps: S1. Weigh out the corresponding amounts of Sc2O3 and MoO3 according to the stoichiometric ratio.

[0070] S2. Place all the raw materials from S1 into a mortar, add 2 mL of anhydrous ethanol, and grind until they are mixed evenly to obtain a mixture.

[0071] S3. Place the mixture in a muffle furnace for high-temperature calcination. First, raise the temperature to 500°C at a rate of 5°C / min and hold for 6 hours; then raise the temperature to 900°C at a rate of 5°C / min and hold for another 4 hours.

[0072] S4. After calcination, allow the sample to cool naturally to room temperature, then grind the sample into powder again to obtain 0% Tm doped sample. 3+ Sc2Mo3O 12 Phosphor based.

[0073] Comparative Example 2 A phosphor based on a negative thermal expansion material, with the chemical formula Sc2Mo3O 12 0.01Tm 3+ .

[0074] The above-mentioned method for preparing phosphors based on negative thermal expansion materials includes the following steps: S1. Weigh out the corresponding amounts of Sc2O3, MoO3, and Tm2O3 according to the stoichiometric ratio.

[0075] S2. Place all the raw materials from S1 into a mortar, add 2 mL of anhydrous ethanol, and grind until they are mixed evenly to obtain a mixture.

[0076] S3. Place the mixture in a muffle furnace for high-temperature calcination. First, raise the temperature to 500°C at a rate of 5°C / min and hold for 6 hours; then raise the temperature to 900°C at a rate of 5°C / min and hold for another 4 hours.

[0077] S4. After calcination, allow the sample to cool naturally to room temperature, and then grind the sample into powder again to obtain 1% Tm doped sample. 3+ Sc2Mo3O 12 Phosphor based.

[0078] Comparative Example 3 A phosphor based on a negative thermal expansion material, with the chemical formula Sc2Mo3O 12 0.05Tm 3+ .

[0079] The above-mentioned method for preparing phosphors based on negative thermal expansion materials includes the following steps: S1. Weigh out the corresponding amounts of Sc2O3, MoO3, and Tm2O3 according to the stoichiometric ratio.

[0080] S2. Place all the raw materials from S1 into a mortar, add 2 mL of anhydrous ethanol, and grind until they are mixed evenly to obtain a mixture.

[0081] S3. Place the mixture in a muffle furnace for high-temperature calcination. First, raise the temperature to 500°C at a rate of 5°C / min and hold for 6 hours; then raise the temperature to 900°C at a rate of 5°C / min and hold for another 4 hours.

[0082] S4. After calcination, allow the sample to cool naturally to room temperature, then grind the sample into powder again to obtain 5% Tm doped sample. 3+ Sc2Mo3O 12 Phosphor based.

[0083] Comparative Example 4 A phosphor based on a negative thermal expansion material, with the chemical formula Sc2Mo3O 12 0.08Tm 3+ .

[0084] The above-mentioned method for preparing phosphors based on negative thermal expansion materials includes the following steps: S1. Weigh out the corresponding amounts of Sc2O3, MoO3, and Tm2O3 according to the stoichiometric ratio.

[0085] S2. Place all the raw materials from S1 into a mortar, add 2 mL of anhydrous ethanol, and grind until they are mixed evenly to obtain a mixture.

[0086] S3. Place the mixture in a muffle furnace for high-temperature calcination. First, raise the temperature to 500°C at a rate of 5°C / min and hold for 6 hours; then raise the temperature to 900°C at a rate of 5°C / min and hold for another 4 hours.

[0087] S4. After calcination, allow the sample to cool naturally to room temperature, then grind the sample into powder again to obtain 8% Tm doped sample. 3+ Sc2Mo3O 12 Phosphor based.

[0088] Comparative Example 5 A phosphor based on a negative thermal expansion material, with the chemical formula Sc2Mo3O 12 0.10Tm 3+ .

[0089] The above-mentioned method for preparing phosphors based on negative thermal expansion materials includes the following steps: S1. Weigh out the corresponding amounts of Sc2O3, MoO3, and Tm2O3 according to the stoichiometric ratio.

[0090] S2. Place all the raw materials from S1 into a mortar, add 2 mL of anhydrous ethanol, and grind until they are mixed evenly to obtain a mixture.

[0091] S3. Place the mixture in a muffle furnace for high-temperature calcination. First, raise the temperature to 500°C at a rate of 5°C / min and hold for 6 hours; then raise the temperature to 900°C at a rate of 5°C / min and hold for another 4 hours.

[0092] S4. After calcination, allow the sample to cool naturally to room temperature, and then grind the sample into powder again to obtain 10% Tm doped sample. 3+ Sc2Mo3O 12 Phosphor based.

[0093] Comparative Example 6 A phosphor based on a negative thermal expansion material, with the chemical formula Sc2Mo3O 12 0.15Tm 3+ .

[0094] The above-mentioned method for preparing phosphors based on negative thermal expansion materials includes the following steps: S1. Weigh out the corresponding amounts of Sc2O3, MoO3, and Tm2O3 according to the stoichiometric ratio.

[0095] S2. Place all the raw materials from S1 into a mortar, add 2 mL of anhydrous ethanol, and grind until they are mixed evenly to obtain a mixture.

[0096] S3. Place the mixture in a muffle furnace for high-temperature calcination. First, raise the temperature to 500°C at a rate of 5°C / min and hold for 6 hours; then raise the temperature to 900°C at a rate of 5°C / min and hold for another 4 hours.

[0097] S4. After calcination, allow the sample to cool naturally to room temperature, and then grind the sample into powder again to obtain 15% Tm doped sample. 3+ Sc2Mo3O 12 Phosphor based.

[0098] The structure and performance of the phosphors based on negative thermal expansion materials prepared in Examples 1 to 5 and Comparative Examples 1 to 6 were tested.

[0099] Figure 1 The images show the XRD patterns of the phosphors used in Examples 1 to 5 and Comparative Examples 1 to 6 of this invention. Figure 1 Figure (a) shows the phosphor images of Comparative Examples 1 to 6, and Figure (b) shows the XRD patterns of the phosphors of Examples 1 to 5. Figure 1 It can be seen that it is similar to the standard card PDF#21-1329 (Sc2Mo3O) 12 The extremely high matching degree indicates that the doped sample neither generated impurity phases nor altered the original crystal structure of the matrix. Regardless of Tm... 3+ Ion doping alone, or Dy 3+ With Tm 3+ Ion co-doping, in these doping modes, Dy 3+ With Tm 3+ The incorporation of ions only causes extremely small changes in the matrix lattice and does not damage the original crystallographic properties of the material.

[0100] Figure 2 This is a SEM image of the phosphor prepared in Example 1 of the present invention. Figure 2 Image (a) is a SEM image at 2 μm, and image (b) is a SEM image at 20 μm. Figure 2 The sample is composed of uniform microcrystalline particles with a smooth surface and relatively regular particle shape, exhibiting no obvious agglomeration or pores, indicating that the phosphor material has good crystallinity and dispersibility. The narrow particle size distribution suggests good control of grain growth during synthesis, resulting in a uniform microstructure. This indicates the successful synthesis of Tm. 3+ ,Dy 3+ Doped Sc2Mo3O 12 Fluorescent powder.

[0101] Figure 3 This is an elemental distribution diagram of the phosphor prepared in Example 1 of the present invention. Figure 3Figure (a) shows the distribution of Dy, (b) shows the distribution of Tm, (c) shows the distribution of Sc, (d) shows the distribution of Mo, and (e) shows the distribution of O. Figure 3 It can be seen that oxygen (O), thulium (Tm), scandium (Sc), dysprosium (Dy) and molybdenum (Mo) elements are uniformly dispersed inside the sample particles, and no obvious aggregation phenomenon is observed.

[0102] Figure 4 These are the spectra of the phosphors of Comparative Examples 1 to 6 of this invention under 354 nm ultraviolet light excitation. Figure 4 It can be seen that when 354nm ultraviolet light is used for excitation, as Tm... 3+ As the doping concentration increases, the luminescence intensity first increases and then decreases at Tm. 3+ The concentration reaches its maximum at 5%, therefore a doping concentration of 5% was selected for further experiments.

[0103] Figure 5 These are the spectra of the phosphors from Examples 1 to 5 of this invention under 354 nm ultraviolet light excitation. Figure 5 It can be known that it contains 5% Tm 3+ And Dy 3+ Samples with doping levels ranging from 1% to 5% all exhibited two sets of characteristic emission peaks: blue light emission at 460 nm (corresponding to Tm 3+ of 1 D2→ 3 F4 energy level transition), yellow light emission at 577nm (originating from Dy) 3+ of 4 F 9 / 2 → 6 H 13 / 2 (Transition). A comparison revealed that the dual-doped sample (0.05Tm) 3+ +yDy 3+ The luminescence intensity of Tm-doped Tm is generally lower than that of Tm-doped Tm. 3+ Sample. With Dy 3+ As the doping concentration increases, the characteristic emission of this ion exhibits a regular pattern of first increasing to a peak and then decreasing. When Dy 3+ When the doping concentration reaches 4%, the emission intensity reaches its peak; further increasing the doping concentration leads to a decrease in luminescence, indicating that a concentration quenching effect has occurred. Analysis reveals that this system contains a concentration quenching effect from Tm... 3+ To Dy 3+ Energy transfer, which makes Dy 3+ Using what originally belonged to Tm 3+ The excitation energy, the blue light emission intensity at 460 nm, varies with Dy 3+ The concentration increases and then decreases.

[0104] Figure 6The Sc2Mo3O of the present invention 12 5%Tm 3+ yDy 3+ A schematic diagram of the energy transfer process. (From...) Figure 6 It can be seen that under 354nm excitation, Tm 3+ The ion first captures the energy of the incident photon, exciting its electrons to... 1 The D2 energy level forms a stable electron distribution. The excited Tm... 3+ The ion does not return to the ground state entirely through radiative transitions, but rather transfers some energy to the neighboring Dy ion through efficient radiative transitions. 3+ Ions. This energy transfer mechanism fills Dy 3+ of 4 I 15 / 2 The energy level prepares for subsequent radiative transitions. At 459 nm, 486 nm, 577 nm, and 667 nm, Tm... 3+ occur 1 D2→ 3 F4 jump, after receiving energy, Dy 3+ Ionic 4 F 9 / 2 Electrons at energy levels become unstable and undergo multiple radiative transitions to lower energy levels. 6 H-series energy levels ( 6 H 15 / 2 → 4 I 15 / 2 , 4 F 9 / 2 → 6 H 15 / 2 , 4 F 9 / 2 → 6 H 13 / 2 and 4 F 9 / 2 → 6 H 11 / 2 ).

[0105] Next, in order to verify the Tm of the embodiment of the present invention 3+ and Dy 3+ The energy transfer process between ions, using Comparative Example 3 (Sc2Mo3O) 12 5% Tm doping in the matrix 3+ As a control group, the lifetime of the phosphor material was tested.

[0106] The decay curve was fitted using a double exponential lifetime decay fitting formula, the calculation formula of which is as follows: .

[0107] Where I is the luminous intensity, I0 is the background or detector zero offset, A1 and A2 are constants, and τ1 and τ2 are exponential decay components.

[0108] Mean lifespan τ* is calculated using the following formula: .

[0109] Where A1 and A2 are constants, and τ1 and τ2 are exponentially decaying components.

[0110] Based on Dexter's energy transfer efficiency formula, energy transfer efficiency η The calculation is as follows: .

[0111] in, It is Sc2Mo3O 12 5%Tm 3+ yDy 3+ The lifetime of fluorescent materials It is Sc2Mo3O 12 5%Tm 3+ Lifetime of fluorescent materials.

[0112] Figure 7 Table 1 shows the lifetime of the phosphors used in Examples 1-5 and Comparative Example 3 of this invention. Table 1 also shows the energy transfer efficiency of the phosphors used in Examples 1-5 and Comparative Example 3. Figure 7 As shown in Table 1, the energy transfer efficiency increased from 11.74% to 28.02%, which further confirms that Sc2Mo3O 12 5%Tm 3+ yDy 3+ Tm in fluorophores 3+ and Dy 3+ Energy transfer occurs between ions.

[0113] Table 1. Energy transfer efficiency of phosphors in Examples 1-5 and Comparative Example 3. The luminescence-thermal stability of fluorescent materials is one of the key indicators for evaluating their practical application potential. Therefore, the luminescence-thermal stability of the fluorescent material in Example 1 of this invention was tested.

[0114] Figure 8 Sc2Mo3O is the Sc2Mo3O of Embodiment 1 of the present invention. 12 5%Tm 3+ 4%Dy 3+ Temperature-dependent spectra of phosphors excited at 354 nm. Figure 8 The smaller image shows Sc2Mo3O under 354nm excitation. 12 5%Tm3+ 4%Dy 3+ A graph showing the relationship between the luminescence intensity of the phosphor at 577 nm wavelength and temperature. Figure 8 It can be seen that Sc2Mo3O 12 5%Tm 3+ 4%Dy 3+ The fluorescence spectrum under 354 nm excitation changes with increasing temperature. As temperature increases, Tm... 3+ The emission intensity at 454 nm gradually decreases, while Dy 3+ The luminescence intensity at 577 nm also shows a decreasing trend, especially in co-doped systems (Tm 3+ / Dy 3+ Co-doping), increased temperature may damage the sensitizer (Tm). 3 + ) and activator (Dy 3+ Highly efficient energy transfer between β-SiAlON and Eu. As the temperature rises to 200℃, the luminescence intensity reaches 60% of that at room temperature, higher than β-SiAlON:Eu. 2+ The phosphor's luminescence intensity retention rate is 48%.

[0115] To investigate Sc2Mo3O 12 5%Tm 3+ 4%Dy 3+ The good thermal stability of phosphors is explained by calculating the thermal quenching activation energy using the following equation: .

[0116] Where I0 is the luminescence intensity of the phosphor at room temperature, I T Let Ea be the luminescence intensity at different temperatures, A be a constant, and k be the Boltzmann constant, with a value of 8.629 × 10⁻⁶. -5 eV / K.

[0117] Through logarithmic transformation, the above formula can be converted into a linear relationship: .

[0118] Figure 9 Sc2Mo3O is the Sc2Mo3O of Embodiment 1 of the present invention. 12 5%Tm 3+ 4%Dy 3+ Activation energy diagram of phosphors. Figure 9The slope of the linear fitting curve is 2414.9, from which the activation energy Ea at 347 nm excitation is calculated to be 0.2083 eV. This is comparable to 0.114 eV for other phosphors, such as Lu₂Ge₂O₇ (data from Ouertani, G., Maciejewska, K., Piotrowski, W., et al. High thermal stability of warm white emitting singlephase GdPO₄: Dy 3+ / Sm 3+ phosphor for UV excited wLEDs. Journal of Luminescence. (2024) , 265, 120228.), Na5Y9F 32 :Dy 3+ / Sm 3+ Compared to Sc2Mo3O, the phosphor's 0.141 eV (data from Xu, F., Zhou, X., Xia, H., Song, et al. Journal of Physics and Chemistry of Solids. 2021, 158, 110240) 12 5%Tm 3+ 4%Dy 3+ The activation energy is significantly higher.

[0119] Based on the chromaticity coordinates of the International Commission on Illumination (CIE) in 1931, this invention provides a systematic and detailed analysis of Sc2Mo3O. 12 5%Tm 3+ y%Dy 3+ The emission color of phosphors (Examples 1 to 5) under 354nm excitation. Figure 10 The present invention is Sc2Mo3O 12 5%Tm 3+ y%Dy 3+ CIE diagram of phosphor. (By...) Figure 10 It can be seen that when Dy 3+ When the ion concentration (y value) is set to 0.04 and 0.05, Sc2Mo3O 12 5%Tm 3+ y%Dy 3+ The phosphor's CIE chromaticity coordinates under 354 nm excitation are located in the white region. This indicates that by optimizing the doping ratio of rare earth ions, the emission color of the phosphor can be effectively controlled to achieve tunable single-phase cool white light. Table 2 shows the Sc2Mo3O 12 5%Tm 3+y%Dy 3+ CIE chromaticity coordinates and color temperature of the phosphor. Table 2 shows that when Dy... 3+ When the ion concentration is 4%, Sc2Mo3O 12 5%Tm 3+ 4%Dy 3+ The CIE chromaticity coordinates of the phosphor are (0.3311, 0.2877), which are very close to the ideal white light coordinates (0.33, 0.33). This invention adjusts Tm... 3+ and Dy 3+ By adjusting the ion concentration, the phosphor successfully achieved a color transition from blue light to white light emission.

[0120] Table 2 Sc2Mo3O 12 5%Tm 3+ y%Dy 3+ CIE chromaticity coordinates and color temperature of phosphors It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range, as well as any value between the two endpoints, can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of this invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended scope of protection is intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of this invention.

[0121] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of protection of this invention and its equivalents, this invention also intends to include these modifications and variations.

Claims

1. A phosphor based on a negative thermal expansion material, characterized in that, The phosphor is made of Sc2Mo3O 12 Matrix, co-doped Tm 3+ and Dy 3+ Ion formation; the chemical formula of the phosphor is Sc2Mo3O. 12 xTm 3+ yDy 3+ Among them, Tm 3+ With a matrix doping concentration x of 5 at.%, Dy 3+ The doping amount y in the matrix is ​​1 at.% to 5 at.%.

2. The phosphor based on a negative thermal expansion material according to claim 1, characterized in that, y is 4at.%.

3. The phosphor based on a negative thermal expansion material according to claim 2, characterized in that, The chromaticity coordinates of the phosphor are (0.3311, 0.2877), and the color temperature is 3010K.

4. A method for preparing phosphor based on a negative thermal expansion material according to any one of claims 1 to 3, characterized in that, Includes the following steps: Sc₂O₃, MoO₃, Tm₂O₃, and Dy₂O₃ were weighed according to stoichiometric ratios and mixed to obtain a mixture; the mixture was then calcined to form Tm₂O₃. 3+ / Dy 3+ Co-doped Sc2Mo3O 12 The structure was obtained to produce a phosphor based on a negative thermal expansion material.

5. The method for preparing phosphor based on negative thermal expansion material according to claim 4, characterized in that, Calcination refers to first heating to 480℃~520℃ and holding at that temperature for 5.5h~6.5h, then heating to 880℃~920℃ and holding at that temperature for another 3.5h~4.5h.

6. The method for preparing phosphor based on negative thermal expansion material according to claim 4, characterized in that, During the calcination process, the heating rate is 3℃ / min to 10℃ / min.

7. The method for preparing phosphor based on negative thermal expansion material according to claim 4, characterized in that, After mixing, the mixture is ground to obtain a mixture. Anhydrous ethanol needs to be added before grinding. The volume ratio of anhydrous ethanol to the mixture is 1:

1.

8. The application of the phosphor based on negative thermal expansion material as described in any one of claims 1 to 3 in a white light emitting diode.

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