NaLi3SiO4 matrix-doped Mn < 2 + >-based red light emitting material and preparation method thereof

Abstract

The invention belongs to the technical field of inorganic luminescent materials, and discloses a NaLi3SiO4 matrix Mn < 2 + >-doped red light luminescent material and a preparation method thereof. The material takes NaLi3SiO4 as a matrix, Mn < 2 + > ions are doped, and in a crystal structure of the material, the Mn < 2 + > ions occupy an eight-coordinate environment of Na < + > ions, so that the material generates red light emission of 677-698 nm under excitation of 428 nm. The luminescent material has excellent spectral performance, and with the increase of the doping concentration, the emission intensity is enhanced and the emission wavelength presents red shift. The preparation method of the material is simple, and comprises the following steps: mixing Na2CO3, Li2CO3, SiO2 and MnCO3 in proportion, and sintering at the high temperature of 850 DEG C for 4 hours to obtain the target luminescent material. The luminescent material has good chemical stability and optical performance, and is suitable for LED illumination and display technology.

Description

Technical Field

[0001] The present invention relates to the technical field of inorganic luminescent materials, and particularly to a red-light emitting material based on NaLi 3 SiO 4 matrix doped with Mn 2+ and its preparation method and application. Background Art

[0002] With the rapid development of modern electronic technology, the demand for efficient, long-life, and stable optical materials is increasing day by day. Especially in the fields of light-emitting diode (LED) lighting, display technology, lasers, and other optoelectronic applications, the requirements for high-performance luminescent materials are becoming more and more stringent. Currently, the common red-light emitting materials on the market are mainly based on matrices such as silicates, phosphates, and fluorides, and achieve luminescence by doping rare earth elements or transition metal elements (such as Mn 2+ 、Eu 3+ etc.). However, these existing materials often face problems such as low luminescence efficiency, poor temperature stability, insufficient color purity, or short luminescence lifetime, seriously affecting their applications in high-end lighting and display technologies.

[0003] In recent years, Mn 2+ -doped inorganic luminescent materials have become a research hotspot due to their excellent red-light emission characteristics. Mn 2 + ions have unique d-d transition characteristics and can exhibit bright red luminescence in appropriate matrices. However, the existing Mn 2+ -doped luminescent materials usually have the following defects: (1) Poor crystal structure stability: Many materials are prone to structural changes under high temperature and humid environments, resulting in attenuation of luminescence performance; (2) Limitation of doping concentration: When the doping concentration is relatively high, it may lead to attenuation of luminescence intensity (concentration quenching), affecting the application effect of the material; (3) Limitation of emission wavelength: The position of the red-light emission peak of traditional Mn 2+ -doped materials is limited and cannot meet the spectral performance requirements of different application scenarios.

[0004] To overcome these problems, it is urgently necessary to develop a new type of red-light emitting material with excellent performance. NaLi 3 SiO 4 (sodium lithium silicate) matrix has become a potential matrix material in research due to its good crystal structure, large pore size, and stable chemical properties. By doping Mn 2+ into the NaLi 3 SiO 4 matrix, the Mn 2+ ions can occupy the Na +The position of the ions, thus affecting the optical properties of the material. Since NaLi 3 SiO 4 The matrix itself has high structural stability, so it can effectively improve the stability of the luminescent material in complex environments such as high temperature and humidity, thus meeting the harsh requirements of modern lighting and display technologies for luminescent materials.

[0005] Based on the NaLi 3 SiO 4 matrix, by using the innovative design of Mn 2+ ion doping, a new red luminescent material is proposed, which has high-efficiency red light emission performance, good environmental stability and long service life, and can effectively solve the problems of existing materials in spectral characteristics, thermal stability and concentration quenching. Through the preparation method provided by the present invention, the production process can be simplified while ensuring the high performance of the material, providing a new solution for the application of high-efficiency and stable red luminescent materials. Summary of the Invention

[0006] Aiming at the problems of poor thermal stability and environmental adaptability of existing red phosphors, the present invention provides a red luminescent material based on NaLi 3 SiO 4 matrix doped with Mn 2+ , and its preparation method and application. The red luminescent material is expected to be applicable to LED lighting, display technology and other optoelectronic application fields.

[0007] The object of the present invention is achieved by the following technical solutions:

[0008] The present invention provides a red luminescent material based on NaLi 3 SiO 4 matrix doped with Mn 2+ , characterized in that the chemical formula of the red luminescent material is: Na 1-x Li 3 SiO 4 : x Mn 2+ , where x is the molar percentage of Mn 2+ doping, 1% ≤ x ≤ 10%; the matrix of the red luminescent material is tetragonal NaLi 3 SiO 4 , the space group is I4 1 / a, the unit cell parameters are Z = 16; the doped Mn 2+ occupies the octahedral coordination environment of Na + , and Mn 2+ is located in the channels formed by the tetrahedra of SiO 4 and LiO 4 , where Na+ The position of + is replaced by Mn. 2+ Replacement.

[0009] Furthermore, the luminescence center of the red light-emitting material is Mn, 2+ producing red light emission from 677 nm to ~698 nm, with a Stokes shift of approximately 4684 cm -1 , and the color coordinates are (0.656, 0.343).

[0010] Furthermore, for the red light-emitting material based on NaLi 3 SiO 4 doped with Mn, 2+ the molecular formula of the red light-emitting material is Na 1- x Li 3 SiO 4 : xMn 2+ where the value of x is 1%, 5%, or 10%.

[0011] Furthermore, for the red light-emitting material based on NaLi 3 SiO 4 doped with Mn, 2+ the molecular formula is Na 0.99 Mn 0.01 Li 3 SiO 4 , Na 0.95 Mn 0.05 Li 3 SiO 4 or Na 0.90 Mn 0.10 Li 3 SiO 4 .

[0012] Furthermore, when the red light-emitting material is excited at 428 nm, it shows six significant excitation peaks, located at ~360 nm, ~384 nm, ~428 nm, ~442 nm, and ~514 nm respectively.

[0013] Furthermore, the doped Mn 2+ is embedded in the NaLi 3 SiO 4 matrix lattice, without significantly changing the crystal structure of NaLi 3 SiO 4 , and no other impurity peaks appear.

[0014] Furthermore, when the red light-emitting material is irradiated with 365 nm ultraviolet light, it exhibits red light emission, showing clear red fluorescence emission characteristics.

[0015] Further, the full width at half maximum of the emission band of the red light emitting material is about 2787 cm -1 (about 130 nm), the emission peak of the emission band is located at ~677 nm, showing long-wavelength red light emission.

[0016] Further, the emission intensity of the red light emitting material increases with the increase of the doping concentration of Mn 2+ , and the emission peak wavelength shows a red shift with the increase of the doping concentration of Mn 2+ .

[0017] The present invention also provides a preparation method of a red light emitting material based on NaLi 3 SiO 4 matrix doped with Mn 2+ , comprising the following steps:

[0018] Step 1: According to the chemical formula Na 1-x Li 3 SiO 4 :x Mn 2+ , weigh Na 2 CO 3 , Li 2 CiO 3 , SiO 2 and MnCO 3 , add Na 2 CO 3 , Li 2 CiO 3 , SiO 2 and MnCO 3 into an ethanol solution in proportion, and grind them in an agate mortar until evenly mixed to obtain a raw material mixture;

[0019] Step 2: Sinter the raw material mixture in a reducing atmosphere, the sintering temperature is 850 °C, the sintering time is 4 hours, and the heating rate is 2-4 °C / minute.

[0020] Step 3: Cool the sintered material to room temperature and grind it into powder to obtain the red light emitting material.

[0021] Further, by mass percentage, the ratio of Na 2 CO 3 in the total amount of raw materials > 30%.

[0022] Further, control the amount of MnCO 2+ in the raw materials with 1% to 10% molar percentage of Mn doped in the final red light emitting material. 3

[0023] Further, in Step 2, the reducing atmosphere contains hydrogen.

[0024] Further, in Step 2, the reducing atmosphere further contains an inert gas, such as nitrogen.

[0025] Further, in Step 2, the reducing atmosphere, by volume fraction, is 4%-5% H 2 and 96%-95% N 2 mixed gas.

[0026] Further, during the sintering process, the mixture of Na 2 CO 3 、Li 2 CiO 3 and SiO 2 is uniformly mixed to ensure complete reaction, and a pure NaLi 3 SiO 4 matrix is obtained.

[0027] The present invention also provides an application of a red light-emitting material based on a NaLi 3 SiO 4 matrix doped with Mn 2+ . Specifically, the red light-emitting material is suitable for high-temperature and humid environments, and can maintain stable luminescence performance in high-temperature and humid environments.

[0028] Further, the red light-emitting material is used in LED lighting and display technologies.

[0029] Further, the red light emission of the red light-emitting material has a long service life, and the luminescence intensity changes little at different temperatures, showing good thermal stability.

[0030] The invention also studied the influence of the doping concentration on the luminescence performance. In the Mn 2+ doping concentration range of 1%-10%, the emission intensity increases with the increase of the concentration, and the emission peak position shows a red shift phenomenon. The red light-emitting material can show clear red light emission under a 365 nm ultraviolet lamp.

[0031] In summary, the red light-emitting material based on the NaLi 3 SiO 4 matrix doped with Mn 2+ has excellent luminous efficiency, a broad excitation band, good thermal stability and a long service life, providing a new solution for the application of high-efficiency red light-emitting materials. Its characteristics are as follows:

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] (1) The present invention precisely regulates the doping concentration and doping sites, enabling the prepared material to have excellent red light emission performance, with high luminous efficiency, a wide emission wavelength range, and further optimizing the luminous efficiency, emission wavelength, and spectral purity of the red light emitting material. The luminescence center of the red light emitting material of the present invention is Mn 2+ , generating red light emission with a wavelength ranging from 677 nm to ~698 nm, having better thermal stability, being able to well compensate for the lack of the existing LED emission spectrum in the long wavelength region, and also being able to solve the problem of spectral color migration.

[0034] (2) The crystal structure of the red light emitting material prepared by the present invention is stable and can maintain long-term luminescence performance under high temperature and humid conditions.

[0035] (3) The preparation method of the present invention is simple and controllable. The synthesis temperature of the red light emitting material is lower than that of similar materials, the preparation process has high efficiency, low production cost, and is easy for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 XRD pattern of the pure-phase NaLi 3 SiO 4 matrix material prepared in Example 1, where "PDF#39-0162" represents the powder diffraction file standard card of the NaLi 3 SiO 4 matrix material

[0037] Figure 2 XRD pattern of the luminescent material Na 0.99 Mn 0.01 Li 3 SiO 4 prepared in Example 2

[0038] Figure 3 Room temperature excitation and emission spectra of the luminescent material Na 0.99 Mn 0.01 Li 3 SiO 4 prepared in Example 2

[0039] Figure 4 Chromaticity coordinate diagram of the luminescent material Na 0.99 Mn 0.01 Li 3 SiO 4 prepared in Example 2

[0040] Figure 5 Emission spectra of the luminescent materials with different doping concentrations prepared in Examples 2-4 DETAILED DESCRIPTION OF THE INVENTION

[0041] In order to make those skilled in the art more clearly understand the technical solution of the present invention, the following examples are listed for illustration. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, the modifications of various equivalent forms of the present invention by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0042] Example 1

[0043] This embodiment provides a pure phase NaLi 3 SiO 4 A method for preparing a matrix, the method comprising the following steps:

[0044] Step (1): According to the structural formula NaLi 3 SiO 4 The chemical ratio was 30% excess of 0.2067 g (1.950 mmol) Na 2 CO 3 、0.3325g (4.500mmol) Li 2 CO 3 With 0.1803g (3.000mmol) SiO 2 Mix, put in an agate mortar, add anhydrous ethanol and grind and mix thoroughly to obtain a mixture;

[0045] Step (2): Place the mixture described in step (1) in a tube furnace and heat it under 5% H 2 -95%N 2 The mixture was heated to 850°C (by volume fraction) at 3°C / min in a mixed reducing atmosphere and calcined for 4 hours. After cooling to room temperature, the mixture was ground into powder to obtain pure NaLi 3 SiO 4 Matrix material.

[0046] See attached Figure 1 , which is NaLi prepared according to this embodiment 3 SiO 4 X-ray diffraction pattern of the matrix material. The test results show that the prepared NaLi 3 SiO 4 The X-ray diffraction pattern of the matrix material is consistent with the standard card, with no impurity peaks, which is NaLi 3 SiO 4 Pure phase, UCr 4 C 4 Type silicate system, the crystal structure is tetragonal, and the space group is I4 1 / a.

[0047] Example 2

[0048] This embodiment provides a preparation method of Mn 2+ -doped NaLi 3 SiO 4 red light-emitting material with the molecular formula of Na 1- x Li 3 SiO 4 :x Mn 2+ (x = 1%). MnCO 3 is added to the NaLi 3 SiO 4 raw materials at a molar percentage of 1%. After sintering under the same conditions, the red light-emitting material is obtained. The specific steps are as follows:

[0049] Step (1): Using 0.2047 g (1.931 mmol) of Na 2 CO 3 , 0.3325 g (4.500 mmol) of Li 2 CO 3 , 0.1803 g (3.000 mmol) of SiO 2 and 0.0034 g (1%, 0.030 mmol) of MnCO 3 as raw materials, according to the stoichiometric ratio of Na 0.99 Mn 0.01 Li 3 SiO 4 and with Na + in excess by 30%, weigh the above raw materials, add 10 mL of absolute ethanol and grind evenly in an agate mortar to obtain a raw material mixture.

[0050] Step (2): Place the raw material mixture obtained in step (1) in a tube furnace, and heat it to 850 °C at a rate of 3 °C per minute under a mixed reducing atmosphere of 5% H 2 -95% N 2 (by volume fraction) and keep it for roasting for 4 hours; then cool it to room temperature and take it out for grinding to obtain a white powder-like red light-emitting material Na 0.99 Mn 0.01 Li 3 SiO 4 .

[0051] See the appendix Figure 2 , which is the X-ray diffraction pattern of the Na 0.99 Mn 0.01 Li 3 SiO 4 light-emitting material prepared according to this embodiment. The test results show that Mn 2+ ions are successfully doped into NaLi 3 SiO 4matrix, and the crystal structure was not significantly changed.

[0052] See the appendix Figure 3 , which is Na prepared according to this embodiment 0.99 Mn 0.01 Li 3 SiO 4 Room temperature excitation and emission spectra of the luminescent material. Monitoring the emission wavelength of 677 nm at room temperature, Na 0.99 Mn 0.01 Li 3 SiO 4 The excitation spectrum of the luminescent material contains six significant excitation peaks, and these excitation peaks all originate from the d-d transition of Mn 2+ ions from the ground state 6 A 1 ( 6 S) to the excited state, where the excitation peak at a wavelength of 428 nm 6 A 1 ( 6 S) → 4 E, 4 A 1 ( 4 G)] has the highest intensity.

[0053] See the appendix Figure 4 , which is Na prepared according to this embodiment 0.99 Mn 0.01 Li 3 SiO 4 Chromaticity coordinate diagram of the luminescent material, Na 0.99 Mn 0.01 Li 3 SiO 4 The luminescent material exhibits bright red light under 365 nm ultraviolet light, with chromaticity coordinates of (0.656, 0.343). The full width at half maximum of this emission peak is 2787 cm -1 (~130 nm), attributed to 4 T 1 ( 4 G) → 6 A 1 ( 6 S) transition. From this, the Stokes shift value of the emission of Mn 2+ ions is 4684 cm -1 .

[0054] See the appendix Figure 5 , which is Na prepared according to this embodiment 0.99 Mn 0.01 Li 3 SiO 4 Emission spectrum of the luminescent material. Under excitation at 428 nm, Na0.99 Mn 0.01 Li 3 SiO 4 The luminescent material exhibits an emission band with a peak at 677 nm.

[0055] Example 3

[0056] This example provides a preparation of a Mn 2+ doped NaLi 3 SiO 4 red light-emitting material, the molecular formula of which is Na 1- x Li 3 SiO 4 : x Mn 2+ (x = 5%). MnCO 3 was added to the NaLi 3 SiO 4 raw materials at a molar percentage of 5%. After sintering under the same conditions, the red light-emitting material was obtained. The specific steps are as follows:

[0057] Step (1): Using 0.1963 g (1.852 mmol) of Na 2 CO 3 , 0.3325 g (4.500 mmol) of Li 2 CO 3 and 0.1803 g (3.000 mmol) of SiO 2 and 0.0172 g (5%, 0.150 mmol) of MnCO 3 as raw materials, according to the stoichiometric ratio of Na 0.95 Mn 0.05 Li 3 SiO 4 and with Na + in excess by 30%, weigh the above raw materials, add 10 mL of absolute ethanol and grind evenly in an agate mortar to obtain a raw material mixture.

[0058] Step (2): Place the raw material mixture obtained in step (1) in a tube furnace and heat it to 850 °C at a rate of 3 °C per minute under a mixed reducing atmosphere of 5% H 2 -95% N 2 (by volume fraction) and hold for 4 hours of roasting; then cool to room temperature and take out for grinding to obtain a white powder-like red light-emitting material Na 0.95 Mn 0.05 Li 3 SiO 4 .

[0059] See attached Figure 5 , which is Na prepared according to this example0.95 Mn 0.05 Li 3 SiO 4 Emission spectrum of the luminescent material. Under 428 nm excitation, Na 0.95 Mn 0.05 Li 3 SiO 4 The luminescent material exhibits an emission band with a peak at 692 nm. Compared with Na 0.99 Mn 0.01 Li 3 SiO 4 luminescent material, there is a red shift and the emission intensity increases, which is related to inhomogeneous broadening or enhanced electron - phonon coupling.

[0060] Example 4

[0061] This example provides a preparation of a Mn 2+ - doped NaLi 3 SiO 4 red - light luminescent material with the molecular formula Na 1- x Li 3 SiO 4 : x Mn 2+ (x = 10%). MnCO 3 is added to the NaLi 3 SiO 4 raw materials at a molar percentage of 10%. After sintering under the same conditions, the red - light luminescent material is obtained. The steps include:

[0062] Step (1): Using 0.1860 g (1.755 mmol) of Na 2 CO 3 , 0.3325 g (4.500 mmol) of Li 2 CO 3 and 0.1803 g (3.000 mmol) of SiO 2 and 0.0345 g (10%, 0.300 mmol) of MnCO 3 as raw materials, according to the stoichiometric ratio of Na 0.90 Mn 0.10 Li 3 SiO 4 and with Na + in excess by 30%, weigh the above - mentioned raw materials, add 10 mL of absolute ethanol and grind them evenly in an agate mortar to obtain a raw material mixture.

[0063] Step (2): Place the raw material mixture obtained in step (1) in a tube furnace and in 5% H 2 - 95% N 2Roast at 850 °C for 4 hours with a heating rate of 3 °C / minute under a mixed reducing atmosphere (by volume fraction); then cool to room temperature and take out for grinding to obtain a white powder of the red-light emitting material Na 0.90 Mn 0.10 Li 3 SiO 4 .

[0064] See the appendix Figure 5 , which is the emission spectrum diagram of the Na 0.90 Mn 0.10 Li 3 SiO 4 luminescent material prepared according to this example. Under 428 nm excitation, the Na 0.90 Mn 0.10 Li 3 SiO 4 luminescent material exhibits an emission band with a peak at 698 nm. Compared with the Na 0.99 Mn 0.01 Li 3 SiO 4 luminescent material and the Na 0.95 Mn 0.05 Li 3 SiO 4 , a red shift occurs and the emission intensity increases, which is related to inhomogeneous broadening or enhanced electroacoustic coupling.

[0065] The Na 1-x Li 3 SiO 4 :xMn 2+ red-light emitting material prepared in the above examples has a simple process and easily available raw materials. Since it exhibits red-light emission from 677 nm to 698 nm under 428 nm excitation, it can be applied to LED lighting and display technologies, well compensating for the lack of the existing LED emission spectrum in the long-wavelength spectral region and also solving the problem of spectral color migration.

[0066] The applicant declares that the present invention illustrates the technical solutions of the present invention through the above examples, but the present invention is not limited to the above examples, that is, it does not mean that the present invention must rely on the above examples to be implemented. Those skilled in the art should understand that any improvement to the present invention, equivalent measures for each raw material of the products of the present invention, addition of auxiliary components, selection of specific methods, etc. all fall within the protection scope and disclosure scope of the present invention.

[0067] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0068] In addition, it should be noted that, in the various specific technical features described in the above specific embodiments, they can be combined in any appropriate manner without conflict. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods.

Claims

1. A method based on NaLi3SiO4 matrix doped with Mn 2+ The red light emitting material is characterized in that The chemical formula of the red light emitting material is: Na 1-x Li3SiO4:xMn 2+ , where x is Mn 2+ Mole percentage of doping, 1%≤x≤10%; The matrix of the red light emitting material is tetragonal NaLi3SiO4, the space group is I41 / a, and the unit cell parameters are Z = 16; Doped Mn 2+ Occupy Na + The eight-coordinate environment of Mn 2+ Located in the pores formed by SiO4 and LiO4 tetrahedrons, where Na + The position of Mn 2+ Alternative.

2. The method according to claim 1, wherein the NaLi3SiO4 matrix is ​​doped with Mn 2+ The red light emitting material is characterized in that The luminescence peak of the red light luminescent material is located under 428nm excitation, and shows six significant excitation peaks, which are located at ∼360nm, ∼384nm, ∼428nm, ∼442nm, and ∼514nm respectively.

3. The NaLi3SiO4 matrix doped with Mn according to claim 1 2+ The red light emitting material is characterized in that Doped Mn 2+ It is embedded in the NaLi3SiO4 matrix lattice without significantly changing the crystal structure of NaLi3SiO4, and no other impurity peaks appear.

4. The method according to claim 1 based on NaLi3SiO4 matrix doped with Mn 2+ The red light emitting material is characterized in that The red light luminescent material exhibits red light emission under 365nm ultraviolet light irradiation, showing clear red fluorescent emission characteristics.

5. The method according to claim 1 based on NaLi3SiO4 matrix doped with Mn 2+ The red light emitting material is characterized in that The half-peak width of the emission band of the red light luminescent material is about 2787 cm -1 (about 130 nm), and the emission peak of the emission band is located at ~677 nm, showing long-wave red light emission.

6. The method according to claim 1 based on NaLi3SiO4 matrix doped with Mn 2+ The red light emitting material is characterized in that The emission intensity of the red light emitting material increases with the Mn 2+ The emission peak wavelength increases with the increase of the doping concentration of Mn 2+ The increase of doping concentration shows a red shift phenomenon.

7. A method of doping Mn based on NaLi3SiO4 matrix as claimed in any one of claims 1 to 6 2+ The method for preparing a red light luminescent material is characterized in that: The following steps are involved: Step 1: According to the chemical formula NaLi3SiO4:xMn 2+ , weighing Na2CO3, Li2CiO3, SiO2 and MnCO3, adding Na2CO3, Li2CiO3, SiO2 and MnCO3 into an ethanol solution in proportion, grinding in an agate mortar until mixed uniformly, to obtain a raw material mixture; Step 2: sintering the raw material mixture in a reducing atmosphere at a sintering temperature of 850° C. for 4 hours at a heating rate of 2-4° C. / min. The reducing atmosphere is a mixed gas of 4%-5% H2 and 96%-95% N2 by volume fraction; Step 3: Cool the sintered material to room temperature and grind it into powder to obtain the red light luminescent material.

8. The preparation method according to claim 7, characterized in that: Calculated by mass percentage, the ratio of Na2CO3 to the total amount of raw materials is greater than 30%; and / or, doping the final red light emitting material with 1% to 10% molar percentage of Mn 2+ Control the amount of MnCO3 in the raw materials; And / or, during the sintering process, the mixture of Na2CO3, Li2CiO3 and SiO2 is uniformly mixed to ensure complete reaction and obtain a pure NaLi3SiO4 matrix.

9. Use of the red light luminescent material according to any one of claims 1 to 6 or the red light luminescent material prepared by the preparation method according to any one of claims 7 to 8, characterized in that: The red light luminescent material is suitable for use in high temperature and humid environments, and can maintain stable luminescent properties in high temperature and humid environments; And / or, can be used in LED lighting and display technology.

10. The use of the red light luminescent material according to claim 9, characterized in that: The red light emission of the red light luminescent material has a long service life, and the luminous intensity changes little at different temperatures, showing good thermal stability.

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