Red fluorescent transparent ceramic for laser display and preparation method thereof

Abstract

The invention discloses red fluorescent transparent ceramic for laser display and a preparation method of the red fluorescent transparent ceramic. The chemical formula of the transparent ceramic is (K0.99-yLiy) 2 (Si1-xMx) F6: 0.02 Mn < 4 + >, M = Ge or Ti, x is the mole percent of M doping, x is greater than or equal to 0.01 and less than or equal to 0.15, y is the mole percent of Li doping, and y is greater than or equal to 0.03 and less than or equal to 0.45; the preparation method comprises the following steps: preparing nanoscale fluoride powder by adopting a hydrothermal synthesis method, and then preparing the fluorescent transparent ceramic by adopting a hot pressed sintering method. Under the excitation of a blue light LD chip with the wavelength of 450 nm, the red light fluorescent ceramic material prepared by the invention realizes the emission of highlight narrow-band red light with the emission wavelength of about 630 nm, has the full width at half maximum of 20-30 nm, the transmittance of 74-78% and the chromaticity coordinate of about (0.682, 0.322), and can be used in the field of laser display.

Description

Technical Field

[0001] The invention relates to the technical field of inorganic luminescent materials, and in particular to a red fluorescent transparent ceramic for laser display and a preparation method thereof. Background Art

[0002] Laser display technology is a new generation of LD display technology. LD does not have the "efficiency drop" phenomenon and has the advantages of small size, small beam, good collimation, rich and saturated colors, high brightness, ultra-long life, low cost and high environmental protection. Its performance at high input power density is far better than LED. In terms of application, it is more suitable for engineering projection, commercial projectors, digital cinemas, laser TVs, optical communications and other fields.

[0003] At present, the mainstream mode of achieving white light emission of LD light source is "blue light chip + Y3Al5O12∶Ce3+(YAG) yellow phosphor", that is, YAG phosphor converts blue light excitation light into yellow light, and combines with unabsorbed blue light to generate white light. However, due to the lack of emission of YAG phosphor in the red light band, the obtained white light has a high correlated color temperature (CCT) and a low color rendering index (CRI), which limits its application in indoor lighting. Therefore, finding a suitable red fluorescent material to improve the light color quality of white light LD has attracted widespread attention from researchers.

[0004] In recent years, Mn 4+ Doped potassium hexafluorosilicate (K2SiF6:Mn 4+ , KSF) Red phosphor is considered to be an ideal material for improving the quality of white light due to its broadband excitation in the blue light region (~450nm) and efficient emission in the red light region (~630nm) (SIJBOM HF, VERSTRAETE R, JOOS JJ, et al. K2SiF6∶Mn 4+ as ared phosphor for displays and warm-white LEDs: a review of properties and perspectives[J].Opt.Mater.Express,2017,7(9):3332-3365). However, due to the crystal structure of the matrix ions and the doping ions Mn 4+Due to the characteristics of easy price change, KSF phosphor has poor moisture resistance and thermal stability. The traditional method is to use packaging technology to directly coat the epoxy resin or silicone with phosphor dispersed on the chip surface, but this packaging method is not suitable for high-power LD light sources and KSF phosphors. The reasons are: First, the LD chip generates a high-temperature environment when working. Long-term use will cause aging and yellowing of the organic packaging material, resulting in light source attenuation and color temperature drift, thereby reducing the quality of white light; second, the low thermal conductivity of epoxy resin or silicone (0.1~0.2W / (m·K)) will cause local high temperature due to the inability to dissipate heat in time, causing severe thermal quenching of KSF phosphors, thereby affecting its luminescence performance (YUE XM,LIN H,LIN SS,etal.La3Si6N 11 ∶Ce 3+ luminescent glass ceramics applicable to high-power solid-state lighting[J].Chin.J.Lumin.,2020,41(12):1529-1537).

[0005] In the study of KSF phosphor (Wei Lingling. Study on Co-precipitation Synthesis, Structure Characterization and Photoluminescent Properties of K2GeF6: MnPhosphors. University Chemistry [J], 2020, 35 (4): 112-118), although the performance is improved by doping Ge ions to replace Si lattice sites, excessive doping concentration will also lead to a decrease in its transmittance, affecting its transparency, and thus reducing the material performance. Studies have shown that the use of LiF as an additive for ceramic sintering has better particle rearrangement and higher densification rate (W. Luo, R. Xie, M. Ivanov, Y. Pan, H. Kou, J. Li, Effects of LiF on the microstructure and optical properties of hot-pressed MgAl2O4 ceramics, Ceram. Int. 43 (2017) 6891-6897). Other studies have also successfully prepared carbon-free, highly transparent YAG polycrystalline ceramics by adding LiF, but they are all based on the high sintering activity of YAG powder prepared by chemical coprecipitation (A.Katz, E.Barraud, S.Lemonnier, E.Sorrel, M.Eichhorn, S.d'Astorg, A.Leriche, Role of LiFadditive on spark plasma sintered transparent YAG ceramics, Ceram.Int.43(2017)15626-15634). It is particularly important to improve the stability of KSF system materials by preparing bulk fluorescent ceramic luminescent materials while optimizing the system and maintaining its fluorescence properties.

[0006] Hot pressing (HP) is a relatively mature sintering method in the industrial field. It can significantly reduce the sintering temperature and shorten the sintering time, thereby resisting grain growth and obtaining products with fine grains and high density. In recent years, in order to shield carbon pollution during the sintering process, people have made tantalum, molybdenum, platinum and other metal foil shielding materials (L. Gan, Y.-J. Park, L.-L. Zhu, H.-N. Kim, J.-W. Ko, J.-W. Lee, Highly transparent Nd doped yttria ceramics fabricated by hot pressing with ZrO2 and La2O3as sintering additives, J. Alloys Compd. 763 (2018) 192-198). These materials have achieved certain effects in preventing carbon pollution and improving sample performance, but the ability to alleviate the fragmentation of ceramic samples during the cooling process is weak, and there are few studies on their application in the sintering of fluoride phosphor powders.

[0007] Based on this, a preparation method of red fluorescent transparent ceramics for laser display is proposed. Summary of the invention

[0008] One of the purposes of the present invention is to provide a red fluorescent transparent ceramic for laser display.

[0009] The second object of the present invention is to provide a method for preparing the above-mentioned red fluorescent transparent ceramic for laser display

[0010] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0011] The first aspect of the present invention provides a red fluorescent transparent ceramic for laser display, the chemical formula of the transparent ceramic is (K 0.99-y Li y )2(Si 1-x M x )F6:0.02Mn 4+ , wherein M=Ge or Ti, x is the molar percentage of M doping, 0.01≤x≤0.15, y is the molar percentage of Li doping, 0.03≤y≤0.45; a nano-scale fluoride powder is first prepared by a hydrothermal synthesis method, and then the fluorescent transparent ceramic is prepared by a hot pressing sintering method.

[0012] The second aspect of the present invention provides a method for preparing the above-mentioned red fluorescent transparent ceramic for laser display, which specifically comprises the following steps:

[0013] (1) According to the molecular formula (K 0.99-y Li y )2(Si 1-x Mx )F6:0.02Mn 4+ Weigh KMnO4 and KHF2 in the stoichiometric ratio, add them to the HF acid solution, stir and dissolve them in an ice bath for 20 to 30 minutes, slowly drop H2O2 solution, wait for a large amount of precipitate K2MnF6 to precipitate, let it stand for 2 to 5 minutes, and pour off the supernatant; wash the precipitate with acetone 2 to 5 times and dry it; where M = Ge or Ti, x is the molar percentage of M doping, 0.01≤x≤0.15, y is the molar percentage of Li doping, 0.03≤y≤0.45;

[0014] (2) Weigh SiO2, GeO2 or TiO2, place it in a centrifuge tube, add HF acid solution, and stir for 15 to 20 minutes to completely dissolve it;

[0015] (3) According to the stoichiometric ratio of phosphor (K 0.99-y Li y )2(Si 1-x M x )F6:0.02Mn 4+ , weigh K2MnF6 and add it to the above solution, stirring and mixing for 15 to 20 minutes;

[0016] (4) Weigh KF, place it in a centrifuge tube, add HF acid solution, and stir for 30 to 40 minutes; after it is completely dissolved, add it dropwise to the mixed solution containing SiO2, GeO2 or TiO2, HF and K2MnF6. After the addition is completed, continue stirring for 10 to 20 minutes. At this time, a large amount of yellow precipitate of K2SiGeF6:Mn or K2SiTiF6:Mn is generated;

[0017] (5) washing the precipitate three times with 25% HF acid solution, acetone and anhydrous ethanol respectively, drying it, and then adding 2.0-5.0 wt% of lithium fluoride (LiF) powder as the solid raw material to obtain the final product (K 0.99-y Li y )2(Si 1- x M x )F6:0.02Mn 4+ Phosphor;

[0018] (6) In an inert atmosphere, weigh (K 0.99-y Li y )2(Si 1-x M x )F6:0.02Mn 4+ The phosphor is loaded into a graphite mold coated with an appropriate amount of flexible hexagonal boron nitride (BN-h) powder;

[0019] (7) placing the graphite mold in a vacuum hot pressing sintering furnace for vacuum sintering;

[0020] (8) The sintered samples are annealed in air and all samples are double-sided polished to obtain red light fluorescent ceramic materials.

[0021] Preferably, the drying temperature in step (1) is 50-60° C., and the drying time is 2-4 hours.

[0022] Preferably, the vacuum sintering temperature in step (1) is 700-900° C., and the sintering time is 1-2 hours.

[0023] Preferably, the annealing temperature in step (1) is 400° C. to 500° C., and the annealing time is 3 to 4 hours.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The red light fluorescent ceramic material prepared by the present invention realizes high-brightness narrow-band red light emission with an emission wavelength of about 630nm under the excitation of a blue light LD chip with a wavelength of 450nm, a half-width of 20-30nm, a transmittance of 74-78%, and a color coordinate of about (0.682, 0.322), and can be used in the field of laser display.

[0026] 2. The present invention uses cheap and effective lithium fluoride (LiF) powder inside the material as a sintering aid and decarburizer for the ceramic. After doping with M (M = Ge or Ti), the original cubic KSF system gradually transforms into a hexagonal system, and the transmittance decreases accordingly. Therefore, the present invention uses Li to partially replace the K site in the lattice substitution, ensuring that the cubic phase of the material system is still maintained under high doping of Ge or Ti, thereby increasing the transmittance of the material. At the same time, lithium fluoride LiF powder as a sintering aid has excellent performance in reducing the specific surface energy of the material and achieving the densification degree of fluoride fluorescent ceramics.

[0027] 3. Compared with the traditional hot pressing sintering, the present invention uses graphite foil as a protective measure on the outside of the material. The graphite foil itself and the graphite mold are also made of graphite, which has a certain degree of carbon pollution on the sintered material. Since boron nitride (BN) has a small friction coefficient, good high-temperature stability, and high thermal conductivity, its carbon shielding performance is similar to that of precious metal foils such as tantalum, molybdenum, and platinum. The use of hexagonal boron nitride (BN-h) powder can not only prevent carbon pollution of the graphite mold during HP sintering, but also prevent the sample from being broken during the cooling process due to the inconsistency of the thermal expansion coefficient of the sample with the mold.

[0028] 4. The present invention uses self-synthesized nanoscale (K 0.99-y Li y )2(Si 1-x Mx )F6:0.02Mn 4+ (M=Ge or Ti) Fluoride powder is hot pressed and sintered into ceramics, which reduces the sintering temperature and prepares red transparent fluorescent ceramics with high thermal stability, effectively solving the problem of insufficient red light component of current fluorescent materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The nanometer scale (K 0.96 Li 0.03 )2(Si 0.99 Ge 0.01 )F6:0.02Mn 4+ Fluorescence spectrum of fluoride powder;

[0030] Figure 2 is prepared in Example 1 of the present invention (K 0.96 Li 0.03 )2(Si 0.99 Ge 0.01 )F6:0.02Mn 4+ Red fluorescent transparent ceramic fluorescence spectrum;

[0031] Figure 3 is prepared in Example 1 of the present invention (K 0.96 Li 0.03 )2(Si 0.99 Ge 0.01 )F6:0.02Mn 4+ Chromaticity diagram of red fluorescent transparent ceramics;

[0032] Figure 4 is prepared in Example 1 of the present invention (K 0.96 Li 0.03 )2(Si 0.99 Ge 0.01 )F6:0.02Mn 4+ Red fluorescent transparent ceramic transmittance curve;

[0033] Figure 5 It is a graph of thermally stable normalized intensity of red fluorescent transparent ceramics prepared in Examples 1-5 of the present invention. DETAILED DESCRIPTION

[0034] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] The raw material powders and reagents used in the following examples are all commercially available products, wherein the purity of the raw material powders KMnO4 and KHF2 is 99.99%, the mass fraction of the HF acid solution is 40%, and the mass fraction of the H2O2 solution is 30%; the purity of acetone is 99.99%; the boron nitride (BN) powder is a flexible hexagonal boron nitride powder with a particle size of 50 to 100 nm.

[0036] Example 1

[0037] According to the chemical formula (K 0.96 Li 0.03 )2(Si 0.99 Ge 0.01 )F6:0.02Mn 4+ Weigh 0.45g KMnO4 and 9.00g KHF2 in the stoichiometric ratio, add to the HF acid solution and stir continuously, dissolve in an ice bath for 20 minutes, slowly add 20 drops of H2O2 solution, let stand for 2 minutes after a large amount of precipitation, and pour off the supernatant. Wash the precipitate twice with acetone, and dry the washed precipitate, i.e. K2MnF6, at about 50℃ for 2 hours.

[0038] Weigh 0.46g SiO2 and 0.56g GeO2, place in a centrifuge tube, add HF acid solution, and stir for 15 minutes to completely dissolve. 0.96 Li 0.03 )2(Si 0.99 Ge 0.01 )F6:0.02Mn 4+ , weigh 0.2g K2MnF6 and add it to the above solution, stir and mix for 15 minutes. Weigh 0.92g KF, place it in a centrifuge tube, add HF acid solution, and stir for 30 minutes. After it is completely dissolved, add it dropwise to the mixed solution of SiO2, GeO2, HF and K2MnF6. After the addition is complete, continue stirring for 10 minutes. At this time, a large amount of K2SiGeF6:Mn yellow precipitate is generated. Wash it three times with 25% mass fraction HF acid solution, acetone and anhydrous ethanol respectively, and finally dry the precipitate at about 50°C for 2 hours, then take it out and cool it to room temperature, add LiF powder which is 2.0wt% of the mass of solid raw materials, and obtain the final product (K 0.96 Li 0.03 )2(Si 0.99 Ge 0.01 )F6:0.02Mn 4+ Phosphor.

[0039] The fluorescent powder is characterized by fluorescence spectrum, such as Figure 1 As shown in the fluorescence spectrum, under the excitation of the blue light LD chip with a wavelength of 450nm, the phosphor achieves high-brightness narrow-band red light emission with an emission wavelength of 630nm and a half-width of 20nm.

[0040] In a glove box filled with argon, 3.00 g of phosphor was weighed and loaded into a graphite mold coated with an appropriate amount of flexible hexagonal boron nitride (BN-h) powder; the graphite mold was placed in a vacuum hot pressing sintering furnace and sintered in a vacuum at 700°C for 1 hour; the sintered sample was annealed in air at 400°C for 3 hours, and all samples were double-sided polished to obtain the red fluorescent transparent ceramic.

[0041] The red fluorescent transparent ceramic is characterized by fluorescence spectrum, such as Figure 2 The fluorescence spectrum is consistent with the fluorescence spectrum of the phosphor. Under the excitation of a blue light LD chip with a wavelength of 450nm, the phosphor achieves high-brightness narrow-band red light emission with an emission wavelength of 630nm and a half-width of 20nm.

[0042] The red fluorescent transparent ceramic was tested by an integrating sphere to obtain the following Figure 3 Chromaticity diagram, color coordinates are (0.682, 0.322).

[0043] The red fluorescent transparent ceramic is characterized by its transmittance, such as Figure 4 The transmittance graph shows that the transmittance of the red fluorescent transparent ceramic is 78%.

[0044] The red fluorescent transparent ceramic is subjected to a thermal stability test, such as Figure 5 , with the increase of temperature, the thermal stability is good and shows a linear change.

[0045] Example 2

[0046] According to the chemical formula (K 0.84 Li 0.15 )2(Si 0.95 Ge 0.05 )F6:0.02Mn 4+ Weigh 0.55g KMnO4 and 11.00g KHF2 in the stoichiometric ratio, add to the HF acid solution and stir continuously, stir and dissolve in an ice bath for 23 minutes, slowly add 22 drops of H2O2 solution, let stand for 3 minutes after a large amount of precipitation, and pour off the supernatant. Wash the precipitate with acetone 3 times, and dry the washed precipitate, i.e. K2MnF6, at about 53°C for 2.5 hours.

[0047] Weigh 0.52g SiO2 and 0.60g GeO2, place in a centrifuge tube, add HF acid solution, and stir for 17 minutes to completely dissolve. 0.84 Li 0.15 )2(Si 0.95 Ge 0.05 )F6:0.02Mn 4+, weigh 0.3g K2MnF6 and add it to the above solution, stir and mix for 17 minutes. Weigh 1.04g KF, place it in a centrifuge tube, add HF acid solution, and stir for 32 minutes. After it is completely dissolved, add it dropwise to the mixed solution of SiO2, GeO2, HF and K2MnF6. After the addition is complete, continue stirring for 12 minutes. At this time, a large amount of K2SiGeF6:Mn yellow precipitate is generated. Wash it three times with 25% HF acid solution, acetone and anhydrous ethanol respectively. Finally, dry the precipitate at about 52°C for 2 hours, take it out and cool it to room temperature, add LiF powder which is 3.0wt% of the mass of the solid raw material, and obtain the final product (K 0.84 Li 0.15 )2(Si 0.95 Ge 0.05 )F6:0.02Mn 4+ Phosphor.

[0048] The fluorescent powder was characterized by fluorescence spectrum, and the fluorescence spectrum was similar to that of Example 1. Under the excitation of a blue light LD chip with a wavelength of 450 nm, the fluorescent powder achieved high-brightness narrow-band red light emission with an emission wavelength of 630 nm and a half-width of 23 nm.

[0049] In a glove box filled with argon, 3.00 g of phosphor was weighed and loaded into a graphite mold coated with an appropriate amount of flexible hexagonal boron nitride (BN-h) powder; the graphite mold was placed in a vacuum hot pressing sintering furnace and sintered in a vacuum at 700°C for 1 hour; the sintered sample was annealed in air at 400°C for 3 hours, and all samples were double-sided polished to obtain the red fluorescent transparent ceramic.

[0050] The fluorescence spectrum of the red fluorescent transparent ceramic was characterized, and the fluorescence spectrum diagram was similar to that of Example 1, and consistent with the fluorescence spectrum of the phosphor. Under the excitation of a blue light LD chip with a wavelength of 450nm, the phosphor achieved high-brightness narrow-band red light emission with an emission wavelength of 630nm and a half-width of 23nm.

[0051] The red fluorescent transparent ceramic was tested by an integrating sphere, and the chromaticity diagram was similar to that of Example 1, with the color coordinates being (0.681, 0.320).

[0052] The transmittance of the red fluorescent transparent ceramic was characterized, and the transmittance graph was similar to that of Example 1. The transmittance of the red fluorescent transparent ceramic was 76%.

[0053] The red fluorescent transparent ceramic is subjected to a thermal stability test, such as Figure 5 , with the increase of temperature, the thermal stability is good and shows a linear change.

[0054] Example 3

[0055] According to the chemical formula (K0.69 Li 0.3 )2(Si 0.9 Ti 0.1 )F6:0.02Mn 4+ Weigh 0.75g KMnO4 and 13.00g KHF2 in the stoichiometric ratio, add to the HF acid solution and stir continuously, dissolve under ice bath for 28min, slowly add 24 drops of H2O2 solution, let stand for 4min after a large amount of precipitation, and pour off the supernatant. Wash the precipitate with acetone 3 times, and dry the washed precipitate, i.e. K2MnF6, at about 55℃ for 2.8h.

[0056] Weigh 0.60g SiO2 and 0.38g TiO2, place in a centrifuge tube, add HF acid solution, and stir for 18 minutes to completely dissolve. 0.69 Li 0.3 )2(Si 0.9 Ti 0.1 )F6:0.02Mn 4+ , weigh 0.5g K2MnF6 and add it to the above solution, stir and mix for 18 minutes. Weigh 1.60g KF, place it in a centrifuge tube, add HF acid solution, and stir for 30 minutes. After it is completely dissolved, add it dropwise to the mixed solution of SiO2, TiO2, HF and K2MnF6. After the addition is complete, continue stirring for 10 minutes. At this time, a large amount of K2SiTiF6:Mn yellow precipitate is generated. Wash it three times with 25% HF acid solution, acetone and anhydrous ethanol respectively. Finally, dry the precipitate at about 50°C for 2 hours, take it out and cool it to room temperature, add LiF powder which is 4.0wt% of the mass of the solid raw material, and obtain the final product (K 0.69 Li 0.3 )2(Si 0.9 Ti 0.1 )F6:0.02Mn 4+ Phosphor.

[0057] The fluorescent powder was characterized by fluorescence spectrum, and the fluorescence spectrum was similar to that of Example 1. Under the excitation of a blue light LD chip with a wavelength of 450 nm, the fluorescent powder achieved high-brightness narrow-band red light emission with an emission wavelength of 630 nm and a half-width of 28 nm.

[0058] In a glove box filled with argon, 3.00 g of phosphor was weighed and loaded into a graphite mold coated with an appropriate amount of flexible hexagonal boron nitride (BN-h) powder; the graphite mold was placed in a vacuum hot pressing sintering furnace and sintered in a vacuum at 700°C for 1 hour; the sintered sample was annealed in air at 400°C for 3 hours, and all samples were double-sided polished to obtain the red fluorescent transparent ceramic.

[0059] The fluorescence spectrum of the red fluorescent transparent ceramic was characterized, and the fluorescence spectrum diagram was similar to that of Example 1, and consistent with the fluorescence spectrum of the phosphor. Under the excitation of a blue light LD chip with a wavelength of 450nm, the fluorescent ceramic achieved high-brightness narrow-band red light emission with an emission wavelength of 630nm and a half-width of 28nm.

[0060] The red fluorescent transparent ceramic was tested by an integrating sphere, and the chromaticity diagram was similar to that of Example 1, with the color coordinates being (0.679, 0.319).

[0061] The transmittance of the red fluorescent transparent ceramic was characterized, and the transmittance graph was similar to that of Example 1. The transmittance of the red fluorescent transparent ceramic was 77%.

[0062] The red fluorescent transparent ceramic is subjected to a thermal stability test, such as Figure 5 , with the increase of temperature, the thermal stability is good and shows a linear change.

[0063] Example 4

[0064] According to the chemical formula (K 0.54 Li 0.45 )2(Si 0.85 Ti 0.15 )F6:0.02Mn 4+ Weigh 0.95g KMnO4 and 14.50g KHF2 in the stoichiometric ratio, add them to the HF acid solution and stir continuously, dissolve in an ice bath for 30 minutes, slowly add 30 drops of H2O2 solution, let stand for 5 minutes after a large amount of precipitation, and pour off the supernatant. Wash the precipitate with acetone 4 times, and dry the washed precipitate, i.e. K2MnF6, at about 60℃ for 3 hours.

[0065] Weigh 0.70g SiO2 and 0.44g TiO2, place in a centrifuge tube, add HF acid solution, and stir for 20 minutes to completely dissolve. 0.54 Li 0.45 )2(Si 0.85 Ti 0.15 )F6:0.02Mn 4+, weigh 0.6g K2MnF6 and add it to the above solution, stir and mix for 20 minutes. Weigh 1.82g KF, place it in a centrifuge tube, add HF acid solution, and stir for 30 minutes. After it is completely dissolved, add it dropwise to the mixed solution of SiO2, TiO2, HF and K2MnF6. After the addition is complete, continue stirring for 10 minutes. At this time, a large amount of K2SiTiF6:Mn yellow precipitate is generated. Wash it three times with 25% HF acid solution, acetone and anhydrous ethanol respectively. Finally, dry the precipitate at about 50°C for 2 hours, take it out and cool it to room temperature, add lithium fluoride powder that is 5.0wt% of the mass of the solid raw material, and obtain the final product (K 0.54 Li 0.45 )2(Si 0.85 Ti 0.15 )F6:0.02Mn 4+ Phosphor.

[0066] The fluorescent powder was characterized by fluorescence spectrum, and the fluorescence spectrum was similar to that of Example 1. Under the excitation of a blue light LD chip with a wavelength of 450 nm, the fluorescent powder achieved high-brightness narrow-band red light emission with an emission wavelength of 630 nm and a half-width of 30 nm.

[0067] In a glove box filled with argon, 3.00 g of phosphor was weighed and loaded into a graphite mold coated with an appropriate amount of flexible hexagonal boron nitride (BN-h) powder; the graphite mold was placed in a vacuum hot pressing sintering furnace and sintered in a vacuum at 700°C for 1 hour; the sintered sample was annealed in air at 400°C for 3 hours, and all samples were double-sided polished to obtain the red fluorescent transparent ceramic.

[0068] The fluorescence spectrum of the red fluorescent transparent ceramic was characterized, and the fluorescence spectrum diagram was similar to that of Example 1, and consistent with the fluorescence spectrum of the phosphor. Under the excitation of a blue light LD chip with a wavelength of 450nm, the fluorescent ceramic achieved high-brightness narrow-band red light emission with an emission wavelength of 630nm and a half-width of 30nm.

[0069] The red fluorescent transparent ceramic was tested by an integrating sphere, and the chromaticity diagram was similar to that of Example 1, with the color coordinates being (0.680, 0.312).

[0070] The transmittance of the red fluorescent transparent ceramic was characterized, and the transmittance graph was similar to that of Example 1. The transmittance of the red fluorescent transparent ceramic was 74%.

[0071] The red fluorescent transparent ceramic is subjected to a thermal stability test, such as Figure 5 , with the increase of temperature, the thermal stability is good and shows a linear change.

[0072] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A red fluorescent transparent ceramic for laser display, It is characterized in that The chemical formula of the fluorescent transparent ceramic is (K 0.99-y Li y ) 2 (Si 1-x M x )F 6 :0.02Mn 4+ , wherein M=Ge or Ti, x is the molar percentage of M doping, 0.01≤x≤0.15, y is the molar percentage of Li doping, 0.03≤y≤0.45; a nano-scale fluoride powder is first prepared by a hydrothermal synthesis method, and then the fluorescent transparent ceramic is prepared by a hot pressing sintering method.

2. A method for preparing the red fluorescent transparent ceramic for laser display according to claim 1, It is characterized in that The specific steps include: (1) According to the molecular formula (K 0.99-y Li y ) 2 (Si 1-x M x )F 6 :0.02Mn 4+ Stoichiometric weighing of KMnO 4 and KHF 2 , add to HF acid solution, stir and dissolve in ice bath for 20-30 min, slowly add H 2 O 2 Solution, wait for a large amount of precipitate K to precipitate 2 Mn 6 After standing for 2 to 5 minutes, the upper clear liquid was poured off; the precipitate was washed with acetone for 2 to 5 times and dried; wherein, M = Ge or Ti, x is the molar percentage of M doping, 0.01≤x≤0.15, y is the molar percentage of Li doping, 0.03≤y≤0.45; (2) Weighing SiO2, GeO 2 or TiO 2 , put it in a centrifuge tube, add HF acid solution, and stir for 15 to 20 minutes to completely dissolve it; (3) According to the stoichiometric ratio of phosphor (K 0.99-y Li y ) 2 (Si 1-x M x )F 6 :0.02Mn 4+ , weigh K 2 Mn 6 Add to the above solution and stir for 15 to 20 minutes; (4) Weigh KF, place it in a centrifuge tube, add HF acid solution, and stir for 30-40 minutes; after it is completely dissolved, add it dropwise to the SiO 2 ,GeO 2 or TiO 2 , HF and K 2 Mn 6 After the addition is completed, continue stirring for 10 to 20 minutes. 2 SiGeF 6 :Mn or K 2 SiTiF 6 : Mn yellow precipitate is generated; (5) washing the precipitate three times with 25% HF acid solution, acetone and anhydrous ethanol respectively, drying, and then adding 2.0-5.0 wt% of lithium fluoride powder as the solid raw material to obtain the final product (K 0.99-y Li y ) 2 (Si 1-x M x )F 6 :0.02Mn 4+ Phosphor; (6) In an inert atmosphere, weigh (K 0.99-y Li y ) 2 (Si 1-x M x )F 6 :0.02Mn 4+ The phosphor is loaded into a graphite mold coated with an appropriate amount of flexible hexagonal boron nitride powder; (7) placing the graphite mold in a vacuum hot pressing sintering furnace for vacuum sintering; (8) The sintered samples are annealed in air and all samples are double-sided polished to obtain red light fluorescent ceramic materials.

3. The method for preparing the red fluorescent transparent ceramic for laser display according to claim 2, It is characterized in that The drying temperature in step (1) is 50-60° C. and the drying time is 2-4 hours.

4. The method for preparing the red fluorescent transparent ceramic for laser display according to claim 2, It is characterized in that The vacuum sintering temperature in step (1) is 700-900° C., and the sintering time is 1-2 hours.

5. The method for preparing the red fluorescent transparent ceramic for laser display according to claim 2, It is characterized in that The annealing temperature in step (1) is 400° C. to 500° C., and the annealing time is 3 to 4 hours.

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