High-entropy oxide red fluorescent material capable of being excited by blue light and preparation method of high-entropy oxide red fluorescent material

Abstract

The invention discloses a high-entropy oxide red fluorescent material capable of being excited by blue light and a preparation method of the high-entropy oxide red fluorescent material, the chemical formula of the high-entropy oxide red fluorescent material is La1-xEux (V0. 2Nb0. 2Ta0. 2Mo0. 2Si0. 2) O4, xlt; 0.12, 0.12; the high-entropy oxide fluorescent material is obtained by taking Eu < 3 + > as an activating agent and La (V < 0.2 > Nb < 0.2 > Ta < 0.2 > Mo < 0.2 > Si < 0.2 >) O4 as a matrix and replacing La < 3 + > ions with Eu < 3 + >. Through 465nm blue light excitation, the yield of red light emitting quantum reaches up to 79.33%; due to the fact that the technology for preparing the 465 nm blue light chip through the InGaN semiconductor technology is mature and mass production is achieved, the cost of a light emitting and displaying device for emitting red light based on blue light excitation Eu < 3 + > ions is much lower than that of a red light device based on ultraviolet light chip excitation. The high-entropy oxide red fluorescent material is simple in preparation process and also has the advantage of being suitable for large-scale production.

Description

Technical Field

[0001] The present invention relates to a red fluorescent material, and particularly to a high-entropy oxide red fluorescent material that can be efficiently excited by blue light and a preparation method thereof, belonging to the field of luminescent materials. Background Art

[0002] Semiconductor light-emitting diodes (LEDs) are a new generation of solid-state lighting products, which have the advantages of high luminous efficiency, energy saving, pollution-free, long life, small size, light weight, etc. They have become the current mainstream lighting and display devices and have great market potential. With the maturity of the III-V semiconductor blue-chip material and process technology, light-converting white light-emitting diodes (WLEDs) that use semiconductor LED chips to excite phosphors and achieve light emission through light-light conversion have become the most widely used light-emitting devices in the fields of general lighting and high-quality displays, occupying the vast majority of the market share of light-emitting products. The maturity of the III-V semiconductor blue-light technology has also become the basis for the rapid development of LEDs.

[0003] According to the principle of colorimetry, white light can generally be obtained by mixing blue, green, and red primary color lights, or can also be achieved by mixing blue light and yellow light. Therefore, there are currently three schemes to realize WLEDs. One is to combine LED chips that emit red, green, and blue lights respectively to achieve white light. This kind of WLED has a high cost due to the complex external circuit. The second scheme is to combine near-ultraviolet LEDs with phosphors that can be effectively excited by this ultraviolet light to emit red, green, and blue primary colors to achieve white light LEDs. Since the ultraviolet chip technology is not yet mature, the luminous efficiency of WLEDs made by this scheme cannot meet the large-scale application of the devices. The third scheme is to combine blue-light LED chips and yellow phosphors that can be effectively excited by blue light to achieve white light LEDs. For example, WLEDs made by exciting YAG:Ce yellow phosphors with InGaN blue light (wavelength of 460 nm) chips have extremely high luminous efficiency. However, this kind of LED emits cold white light, that is, the white light lacks red light components, which limits its wide application in the fields of lighting and display. In addition, the luminous efficiency of red phosphors excited by near-ultraviolet light is low and cannot match that of high-efficiency blue-green phosphors, which also restricts the realization of white light illumination by near-ultraviolet LED chips. Therefore, the development of red phosphors that can be efficiently excited by blue light is extremely important for the wide application of WLEDs.

[0004] Rare earth Eu 3+ ions are commonly used red phosphor activators. When Eu 3+ is doped into the host material and occupies a non-centrosymmetric lattice site, due to 5 D0→ 7 F2 transition, Eu 3+Ions can emit strong red light near 613 nm and are widely used to prepare red fluorescent materials. For example, when Eu 3+ is doped into the C2 site of Y2O3, due to the occurrence of 5 D0→ 7 F2 transition, the phosphor exhibits strong red fluorescence emission. However, when monitoring the excitation spectrum of Eu 3+ for 5 D0→ 7 F2 transition to emit red light, the O 2- →Eu 3+ charge transfer transition located in the ultraviolet region and the 7 F0→ 5 L6 transition located in the near ultraviolet (about 394 nm) that excite the intensity of red light emission are much stronger than the intensity of red light emission generated by the 7 F0→ 5 D2 transition located in the blue light region (about 465 nm). Therefore, based on the blue light chip to excite the luminescence performance of Eu 3+ red phosphors, it is often inferior to the Eu 3+ red-emitting fluorescent materials excited by ultraviolet chips, making the technical maturity and cost advantages of blue light LED chips over ultraviolet LED chips not fully reflected in lighting and display devices. Similarly, in Eu 3+ doped SrWO4, BaMoO4, La(V 0.3 Nb 0.7 )O4 and other red fluorescent materials, there is also a situation where the luminescence intensity of the material excited by near ultraviolet light is much greater than that excited by blue light. Although such materials with a scheelite-tetragonal structure of ABO4 type with tetragonal symmetry are very suitable for Eu 3+ to emit red light, and even the quantum efficiency of red light emission under near ultraviolet light excitation can be as high as more than 90%. To solve the problem of low luminescence efficiency of red fluorescent materials based on Eu 3+ luminescence excited by blue light, it is urgent to explore new ideas for designing red fluorescent materials. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a high-entropy oxide red fluorescent material that can be excited by blue light and a preparation method thereof.

[0006] The present invention is realized by adopting the following technical solutions:

[0007] A blue light-excitable high-entropy oxide red fluorescent material, whose chemical formula is La 1-x Eu x (V 0.2 Nb 0.2 Ta0.2 Mo 0.2 Si 0.2 )O4, (where 0 < x < 0.12), this fluorescent material uses Eu 3+ as the activator, and the high-entropy oxide La(V 0.2 Nb 0.2 Ta 0.2 Mo 0.2 Si 0.2 )O4 as the matrix, and is obtained by doping with Eu 3+ substituting for La 3+ ions.

[0008] Furthermore, the fluorescent material has a tetragonal-symmetric scheelite crystal structure of the ABO4 type, with the space group I41 / a; five metal atoms V, Nb, Ta, Mo, and Si in equimolar amounts are uniformly and disorderly distributed at the B site of the lattice, suppressing phase separation by increasing the configurational entropy of the material to form a stable single-phase high-entropy oxide fluorescent material.

[0009] Furthermore, irradiating this material with near-ultraviolet light at a wavelength of 394 nm and blue light at 465 nm can respectively excite the 3+ of 7 F0→ 5 L6 transition and 7 F0→ 5 D2 transition of Eu 3+ ions, and then induce Eu 5 ions to strongly emit red light with the strongest peak at 614 nm ([[]] 7 D0→ j F[[[]] 5 D0→ 7 F2 transition) through the 3+ D0→ 3+ F[[[]]

[0010] The material design principle of a high-entropy oxide red fluorescent material that can be efficiently excited by blue light is as follows:

[0011] The process of exciting Eu 3+ ions to emit light with 394 nm ultraviolet light and 465 nm blue light can be described as follows: After Eu 3+ ions absorb the photon energy of the excitation light, electrons transition from the ground state 7 F0 to the excited states 5 L6 and 5 D2 respectively. After that, with the participation of phonons, most of the electrons in the excited state will relax to the 5 D0 energy level and then to 7 F[[[]] j(j=0,1,2,3,4) energy level radiative transition, producing orange and red fluorescence. Therefore, the electron transition probability and the electron transition involving phonons have an important influence on the light excitation efficiency. The former is mainly determined by Eu 3+ The crystal field environment in which the ions are located, and the degree of phonon participation in electronic transitions can be controlled by changing the translational symmetry of the material lattice.

[0012] High entropy materials refer to stable single-phase solid solutions formed by atoms of five or more elements occupying the same lattice site of the material in equal or nearly equal moles. Since atoms of different elements occupy the same lattice site, the difference in atomic size will affect the bond length and bond angle between atoms, causing a large lattice distortion, thereby changing Eu 3+ The crystal field environment in which the ions are located affects the transition probability of 4f electrons under light excitation. On the other hand, atoms of different elements occupy the same lattice position and are evenly and disorderly distributed in the crystal, destroying the translational symmetry of the lattice at that position, causing phonon localization, weakened momentum matching of electron transitions, and defect-dominated transition paths, thereby reducing the efficiency of phonon-assisted electron transitions and also having an important regulatory effect on the probability of light-excited electron transitions. Therefore, based on the entropy regulation of materials, it is possible to 3+ More efficient blue light excitation of rare earth ions can be achieved by doping high-entropy fluorescent materials.

[0013] The formation of high entropy materials requires that atoms of multiple elements with equal moles uniformly and disorderly occupy the same lattice position to induce an increase in configurational entropy, so as to overcome the increase in enthalpy caused by multiple atoms entering the lattice, and then inhibit the phase separation of the material due to the increase in free energy. The atoms of five elements, V, Nb, Ta, Mo and Si, are selected to occupy the B position of the ABO4 scheelite lattice. On the one hand, the tetragonal symmetric ABO4 scheelite structure is suitable for Eu 3+ On the other hand, it is because V, Nb, Ta, Mo, and Si atoms easily form stable BO4 tetrahedrons with coordinated oxygen atoms, thereby reducing the enthalpy increase and forming a stable single-phase material.

[0014] The present invention adopts a solid phase reaction method to prepare the above-mentioned chemical formula La 1-x Eu x (V 0.2 Nb 0.2 Ta 0.2 Mo 0.2 Si 0.2 )O4, (where 0 <x<0.12)的高熵氧化物红光荧光材料的工艺步骤如下:

[0015] Weigh appropriate raw material reagents La2O3, Eu2O3, V2O5, Nb2O5, Ta2O5, MoO3, and SiO2 according to stoichiometry. After fully grinding and mixing them evenly, ball mill for 12 hours;

[0016] Then place it in a muffle furnace, raise the temperature to 1000 °C and react for 4 - 6 hours. Then, raise the temperature to a certain temperature between 1300 - 1500 °C and carry out a high-temperature reaction for 10 - 14 hours. After cooling to room temperature and grinding, a high-entropy oxide red fluorescent material with the chemical formula La 1-x Eu x (V 0.2 Nb 0.2 Ta 0.2 Mo 0.2 Si 0.2 )O4, (where 0 < x < 0.12) is prepared.

[0017] In addition, by adding 2% - 5% of K2CO3, H3BO3, BaF2, or BaCl2 as a flux to the mixture of raw material reagents, the synthesis temperature of the high-entropy oxide fluorescent material prepared by the solid-phase reaction method can be reduced to the range of 1200 - 1300 °C, and a pure-phase fluorescent material La 1-x Eu x (V 0.2 Nb 0.2 Ta 0.2 Mo 0.2 Si 0.2 )O4, (where 0 < x < 0.12) can be prepared.

[0018] Advantages of the present invention:

[0019] (1) The present invention provides a high-entropy oxide red fluorescent material that can efficiently emit red light by exciting Eu 3+ ions with 465 nm blue light. The quantum yield of the material emitting red light by exciting with 465 nm blue light is as high as 79.33%; since the process of preparing a 465 nm blue light chip using InGaN semiconductor technology is mature and has been mass-produced, therefore, the cost of the light-emitting and display devices based on exciting Eu 3+ ions to emit red light with blue light is much lower than that of the red light devices excited by ultraviolet light chips. The preparation process of the high-entropy oxide red fluorescent material of the present invention is simple and also has the advantage of being suitable for large-scale production;

[0020] (2) In addition, Eu 3+In low-entropy materials (e.g., SrMoO4) with a scheelite crystal structure of ABO4 type having tetragonal symmetry, the efficiency of emitting red light by exciting the material with ultraviolet light of 394 nm is much higher than that with excitation at 465 nm. In contrast, for the high-entropy oxide La 1-x Eu x (V 0.2 Nb 0.2 Ta 0.2 Mo 0.2 Si 0.2 )O4, although it also has the same crystal structure, the efficiency of Eu 3+ luminescence when excited by 465 nm blue light is stronger than that when excited by 394 nm ultraviolet light. This method of regulating the transition probability of rare-earth ions by entropy engineering to enhance the photoexcitation efficiency of materials also provides a new idea for the research of new rare-earth fluorescent materials. Description of the Drawings

[0021] Figure 1 : X-ray diffraction patterns of the La(V 0.2 Nb 0.2 Ta 0.2 Mo 0.2 Si 0.2 )O4 matrix materials prepared by solid-phase reaction at 1400 °C, 1450 °C, and 1500 °C respectively.

[0022] Figure 2 : X-ray diffraction patterns of the high-entropy oxide red-light fluorescent materials La 1-x Eu x (V 0.2 Nb 0.2 Ta 0.2 Mo 0.2 Si 0.2 )O4, (x = 0.01, 0.03, 0.05, 0.07).

[0023] Figure 3 : Energy spectrum of the high-entropy oxide red-light fluorescent material La 0.95 Eu 0.05 (V 0.2 Nb 0.2 Ta 0.2 Mo 0.2 Si 0.2 )O4.

[0024] Figure 4 : High-entropy oxide fluorescent material La 1-x Eu x (V 0.2 Nb 0.2 Ta 0.2 Mo 0.2 Si 0.2)O4, (x = 0.01, 0.03, 0.05, 0.07) Photoluminescence excitation spectrum (PLE) of 614 nm red light emission.

[0025] Figure 5 : Using 465 nm blue light to excite the high-entropy oxide fluorescent material La 1-x Eu x (V 0.2 Nb 0.2 Ta 0.2 Mo 0.2 Si 0.2 )O4, (x = 0.01, 0.03, 0.05, 0.07) Photoluminescence spectrum (PL).

[0026] Figure 6 : Using 465 nm blue light to excite the high-entropy oxide fluorescent material La 0.95 Eu 0.05 (V 0.2 Nb 0.2 Ta 0.2 Mo 0.2 Si 0.2 )O4 red light emission quantum yield (QY).

[0027] Figure 7 : Using H3BO3 as a cosolvent, the X-ray diffraction pattern of La 0.95 Eu 0.05 (V 0.2 Nb 0.2 Ta 0.2 Mo 0.2 Si 0.2 )O4 prepared by the solid-state reaction method. Specific implementation mode

[0028] Example 1: Preparing the high-entropy oxide La(V 0.2 Nb 0.2 Ta 0.2 Mo 0.2 Si 0.2 )O4 matrix material

[0029] Weigh appropriate raw material reagents La2O3, V2O5, Nb2O5, Ta2O5, MoO3 and SiO2 according to stoichiometry, grind and mix them evenly, and then ball mill for 12 hours; then place them in a muffle furnace, raise the temperature to 1000 °C and react for 4 - 6 hours, and then raise the temperature to a certain temperature T (T = 1400 °C, 1450 °C, or 1500 °C) between 1300 - 1500 °C, and react at high temperature for 10 - 14 hours. After cooling to room temperature and grinding, the high-entropy oxide with the chemical formula La(V 0.2 Nb 0.2 Ta 0.2Mo 0.2 Si 0.2 )O4 high-entropy oxide material.

[0030] The phase and crystal structure of the material were analyzed by X-ray diffraction, as Figure 1 shown, showing the diffraction peaks of the high-entropy oxide La(V 0.2 Nb 0.2 Ta 0.2 Mo 0.2 Si 0.2 )O4 prepared by the solid-state reaction method, which can match the standard PDF#85-1847 card, indicating that a single-phase high-entropy oxide material has been prepared. This material has a tetragonal symmetric ABO4-type scheelite crystal structure, and the space group of the crystal is I41 / a.

[0031] Example 2: Preparation of Eu 3+ -doped high-entropy oxide red fluorescent material La 1-x Eu x (V 0.2 Nb 0.2 Ta 0.2 Mo 0.2 Si 0.2 )O4, (x = 0.01, 0.03, 0.05, 0.07)

[0032] Weighed appropriate raw material reagents La2O3, Eu2O3, V2O5, Nb2O5, Ta2O5, MoO3 and SiO2 according to stoichiometry, ground and mixed them thoroughly, and then ball-milled for 12 hours; then placed them in a muffle furnace, raised the temperature to 1000 °C and reacted for 4 - 6 hours, and then raised the temperature to 1400 °C and reacted at high temperature for 10 - 14 hours. After cooling to room temperature and grinding, the high-entropy oxide red fluorescent material with the chemical formula La 1-x Eu x (V 0.2 Nb 0.2 Ta 0.2 Mo 0.2 Si 0.2 )O4, (x = 0.01, 0.03, 0.05, 0.07) was prepared.

[0033] The phase and crystal structure of the material were analyzed by X-ray diffraction, as Figure 2 shown, showing the La 1-x Eu x (V 0.2 Nb 0.2 Ta 0.2 Mo 0.2 Si0.2 ) The diffraction peaks of O4, (x = 0.01, 0.03, 0.05, 0.07), can also be matched with the standard PDF #85-1847 card, indicating that a single-phase high-entropy oxide material is prepared. This material has a tetragonal-symmetric ABO4-type scheelite crystal structure, and the space group of the crystal is I41 / a. Figure 3 As shown, La 0.95 Eu 0.05 (V 0.2 Nb 0.2 Ta 0.2 Mo 0.2 Si 0.2 ) In O4, each element is evenly distributed without phase separation.

[0034] The excitation spectrum of the material emitting red light at 614 nm was measured using a fluorescence spectrometer. As Figure 4 shown, it was observed that although the ultraviolet light at 394 nm and the blue light at 465 nm can both excite Eu 3+ to emit red light at 614 nm, however, the intensity of the red light emitted by Eu 3+ excited by 465 nm blue light is much greater than that under near-ultraviolet excitation; Figure 5 As shown, when 465 nm blue light is used as the excitation light source to irradiate the high-entropy oxide fluorescent material, strong red light can be generated due to the 3+ of Eu 5 D0→ 7 F2 transition. Figure 6 As shown, when 465 nm blue light is used to excite the high-entropy oxide fluorescent material La 0.95 Eu 0.05 (V 0.2 Nb 0.2 Ta 0.2 Mo 0.2 Si 0.2 )O4, the quantum yield of red light emission reaches 79.33%, indicating that this high-entropy oxide is a highly efficient red-light fluorescent material that can be excited by blue light.

[0035] Example 3: Using H3BO3 as a cosolvent, a high-entropy oxide red-light fluorescent material La 0.95 Eu 0.05 (V 0.2 Nb 0.2 Ta 0.2 Mo 0.2 Si 0.2 )O4

[0036] Weigh appropriate raw material reagents La2O3, Eu2O3, V2O5, Nb2O5, Ta2O5, MoO3 and SiO2 according to stoichiometry. After fully grinding and mixing them evenly, add 3% of H3BO3 to the phase mixture and ball-mill for 12 hours. Then place it in a muffle furnace, raise the temperature to 1000 °C and react for 4 - 6 hours. Then, raise the temperature to 1200 °C and react at high temperature for 10 - 14 hours. After cooling to room temperature and grinding, the high-entropy oxide red fluorescent material La 0.95 Eu 0.05 (V 0.2 Nb 0.2 Ta 0.2 Mo 0.2 Si 0.2 )O4 is prepared.

[0037] The phase and crystal structure of the material prepared by the solid-phase reaction method are analyzed by X-ray diffraction. As Figure 7 shown, it shows that after adding the cosolvent, the solid-phase reaction can be carried out at a lower temperature to prepare a single-phase high-entropy oxide material.

Claims

1. A high-entropy oxide red fluorescent material that can be excited by blue light, characterized in that, Its chemical formula is La 1-x Eu x (V 0.2 Nb 0.2 Ta 0.2 Mo 0.2 Si 0.2 )O4, where 0 < x < 0.12; The high-entropy oxide fluorescent material uses Eu 3+ as the activator and La(V 0.2 Nb 0.2 Ta 0.2 Mo 0.2 Si 0.2 )O4 as the matrix and is obtained by doping with Eu 3+ substituting La 3+ ions.

2. The high-entropy oxide fluorescent material according to claim 1, wherein The high-entropy oxide fluorescent material has a scheelite crystal structure of the ABO4 type with tetragonal symmetry, and the space group is I41 / a; five metal atoms V, Nb, Ta, Mo, and Si in equimolar amounts are uniformly and disorderly distributed at the B-site of the lattice, suppressing phase separation by increasing the configurational entropy of the material to form a stable single-phase high-entropy oxide fluorescent material.

3. The high-entropy oxide fluorescent material according to claim 1, wherein The x is 0.01, 0.03, 0.05, or 0.

07.

4. The high-entropy oxide fluorescent material according to any one of claims 1-3, characterized in that The high-entropy oxide fluorescent material can be excited by 465 nm blue light, and its quantum yield of emitting red light is as high as 79.33%.

5. A method for preparing a high-entropy oxide red fluorescent material that can be excited by blue light according to any one of claims 1-4, characterized in that, It includes the following steps: (1) Prepare the high-entropy oxide La(V 0.2 Nb 0.2 Ta 0.2 Mo 0.2 Si 0.2 )O4 matrix material by the solid-state reaction method; (2) The red fluorescent material of Eu-doped high-entropy oxide La 3+ Eu 1-x Eu x (V 0.2 Nb 0.2 Ta 0.2 Mo 0.2 Si 0.2 )O4 is prepared by a solid-state reaction method; or Add a cosolvent and prepare the entropy oxide red fluorescent material La 1-x Eu x (V 0.2 Nb 0.2 Ta 0.2 Mo 0.2 Si 0.2 )O4.

6. The preparation method according to claim 5, characterized in that, Specifically: Weigh appropriate raw material reagents La2O3, Eu2O3, V2O5, Nb2O5, Ta2O5, MoO3 and SiO2 according to stoichiometry. After fully grinding and mixing them evenly, put them in a ball mill and then place them in a muffle furnace. Heat up to react, and then raise the temperature to 1300 - 1500 °C for high-temperature reaction. After cooling to room temperature and grinding, the compound with the chemical formula La 1-x Eu x (V 0.2 Nb 0.2 Ta 0.2 Mo 0.2 Si 0.2 )O4 is prepared.

7. The preparation method according to claim 6, characterized in that, Specifically: The heating and temperature-rising reaction is to raise the temperature to 1000 °C and react for 4 - 6 hours; The high-temperature reaction at the temperature raised to 1300 - 1500 °C lasts for 10 - 14 hours.

8. The preparation method according to claim 5, characterized in that, Specifically: By adding 2%-5% of K2CO3, H3BO3, BaF2 or BaCl2 as a cosolvent to the mixture of raw material reagents, and placing it in a muffle furnace to control the temperature in the range of 1200-1300°C, a pure-phase fluorescent material La 1-x Eu x (V 0.2 Nb 0.2 Ta 0.2 Mo 0.2 Si 0.2 )O4 is prepared.

9. The preparation method according to claim 8, characterized in that, Controlling the temperature within the range of 1200 - 1300 °C includes: first raising the temperature to 1000 °C and reacting for 4 - 6 hours, then raising the temperature to 1200 °C and performing a high-temperature reaction for 10 - 14 hours, and after cooling to room temperature and grinding, the high-entropy oxide red fluorescent material La 1-x Eu x (V 0.2 Nb 0.2 Ta 0.2 Mo 0.2 Si 0.2 )O4.

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