Submicron rare earth silicate fluorescent powder and preparation method thereof

Abstract

The application provides a sub-micron rare earth silicate fluorescent powder and a preparation method thereof. The preparation method of the sub-micron rare earth silicate fluorescent powder comprises the following steps: coating MReF4 nanocrystals with silicon dioxide to form a MReF4@SiO2 precursor with a core-shell structure, and etching the silicon dioxide after sintering the precursor to obtain the sub-micron rare earth silicate fluorescent powder; wherein M is an alkali metal, and Re is a lanthanide element. The application can realize the preparation of a super-small-size rare earth silicate fluorescent powder by etching the MReF4@SiO2 precursor with a core-shell structure after sintering, and the particle size of the product can be finely controlled by sintering temperature and sintering time. Compared with the prior art, the preparation method has the advantages of easy batch production, narrow particle size distribution range, easy size adjustment and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of material preparation, and particularly relates to a submicron rare earth silicate fluorescent powder and a preparation method thereof. BACKGROUND

[0002] The rare earth activated silicate matrix fluorescent powder has the advantages of narrow band emission, high efficiency, stable performance, etc. The lighting and display devices combined with light emitting diodes (LED) have achieved wide commercial application.

[0003] The traditional preparation of rare earth silicate materials mostly adopts a high-temperature solid-phase sintering method. The rare earth silicate materials produced by the method have large sizes and irregular shapes, which leads to less excitation light scattering in the fluorescent powder, low extraction efficiency of the excitation light, and large deviation of the proportion of the excitation light and the emission light at different angles, and obvious color deviation. In the widely used cerium-activated yttrium aluminum garnet fluorescent powder, there is a typical case of this effect, i.e. "yellow ring". Especially when the fluorescent powder is applied to small-size display or lighting devices, the total amount of the fluorescent powder used is limited, and the color deviation will be more significant. However, the size of the fluorescent powder is not the smaller the better. When the particle size gradually decreases, the light emission quenching caused by surface defects gradually dominates, and the light emission performance of the fluorescent powder is greatly weakened. Therefore, it is of great scientific significance and application value to develop a size-controllable synthesis scheme of the rare earth silicate-based fluorescent powder.

[0004] At present, the preparation strategies of the rare earth silicate submicron crystals are mainly based on the "bottom-up" method. The preparation methods mainly include a spray pyrolysis method, a sol-gel method and a chemical co-precipitation method. Among them, the spray pyrolysis method requires relatively complex equipment, the size of the product is mostly determined by the size of the spray droplets, it is difficult to produce uniform and small droplets in batches, and it is difficult to mass-produce. Limited by the high synthesis temperature of the rare earth silicate, the sol-gel and chemical co-precipitation methods must synthesize the product through high-temperature annealing, which in turn causes unavoidable particle agglomeration, and the product size is still large. SUMMARY

[0005] The present application provides a submicron rare earth silicate fluorescent powder and a preparation method thereof, to solve the defects of uncontrollable size and difficult batch production in the prior art, and to realize the large-scale production of the submicron rare earth silicate fluorescent powder with a narrow particle size distribution range and an easily adjustable size.

[0006] The present application provides a preparation method of a submicron rare earth silicate fluorescent powder, which comprises: coating MReF4 nanocrystals with silicon dioxide to form a MReF4@SiO2 precursor with a core-shell structure, and etching the silicon dioxide after sintering the precursor to obtain the submicron rare earth silicate fluorescent powder; wherein M is an alkali metal, and Re is a lanthanide element.

[0007] In order to overcome the particle agglomeration caused by high-temperature sintering, the application innovatively uses a special precursor to synthesize submicron rare earth silicate fluorescent powder, which is a MReF4@SiO2 core-shell structure nanocrystal. In the core-shell structure, MReF4 is the core, and the SiO2 shell close to the core is the reactant to react with MReF4 to generate rare earth silicate; and the SiO2 far from the core is the medium for the diffusion of rare earth silicate. When the reaction starts, the generated rare earth silicate can be isolated from each other. Further increasing the sintering temperature and sintering time can further promote the diffusion speed of rare earth silicate in SiO2, so as to make it aggregate and grow, and achieve the purpose of size control.

[0008] In some embodiments of the application, M is Li, Na or K, and Re is lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium or lutetium.

[0009] Further, in some embodiments of the application, M is Na, and Re is gadolinium (Gd). That is, the product obtained is a sodium gadolinium silicate-based fluorescent powder, which has a higher quantum efficiency and better color purity, and is more outstanding in rare earth silicate fluorescent powder.

[0010] In some embodiments of the application, the preparation of the precursor comprises: mixing and reacting MReF4 nanocrystals with a surfactant, cyclohexane, n-hexane, ammonia, hydrochloric acid and tetraethyl silicate, and then precipitating with ethanol and acetone.

[0011] The surfactant is one or more of IGEPAL CA-630, IGEPAL CA-720, IGEPAL CA-730, IGEPAL CO-520 and IGEPAL CO-890.

[0012] In the embodiment where M is Na and Re is Gd, the surfactant is preferably IGEPAL CO-520 (polyoxaethylene (5) nonylphenyl ether).

[0013] Further, the reaction temperature in the preparation process of the precursor is 125-135℃, and the time is 10-16 hours.

[0014] Further, the volume ratio of the surfactant, cyclohexane, n-hexane, ammonia, hydrochloric acid and tetraethyl silicate is (0.05-10):(0-30):(0-30):(0-0.2):(0-0.2):(0.002-1). It should be noted that cyclohexane and n-hexane are solvents, and their volumes are not zero at the same time; ammonia and hydrochloric acid are catalysts, and either one of them is optional.

[0015] In some embodiments of the present application, the sintering temperature is 500-1200℃, preferably 600-700℃, and the sintering time is 1-5 minutes.

[0016] In the preparation method of the present application, different sintering temperatures and time can be used to obtain rare earth silicate fluorescent powder with different sizes. When the sintering temperature is controlled in the range of 500-1200℃, the particle size of the product can be controlled in a reasonable range. When the sintering temperature is further controlled in the range of 600-700℃ and the sintering time is 1-5 minutes, the particle size distribution of the obtained rare earth silicate fluorescent powder can be more narrow and concentrated in a suitable particle size range.

[0017] In some embodiments of the present application, M is Na and Re is Gd, and the sintering temperature is preferably controlled in the range of 600℃, and the obtained sub-micron NaGd9Si6O 26 The particle size of the fluorescent powder is concentrated around 550nm.

[0018] In some embodiments of the present application, the alkali solution is sodium hydroxide solution, and the concentration is 20-200g / L, and further preferably 80-120g / L.

[0019] Further, the reaction temperature for etching silicon dioxide using sodium hydroxide solution is 170-190℃, and more preferably 180℃.

[0020] The MReF4 nanocrystals used in the present application can be prepared according to the prior art.

[0021] For example, the reaction can be carried out by mixing oleic acid, ethanol, alkali hydroxide, rare earth compound, water and ammonium fluoride. The rare earth compound can be chloride or nitrate compound of various lanthanide ions, and can be anhydrous compound or hydrate thereof.

[0022] Further, the molar ratio of oleic acid, ethanol, alkali hydroxide, rare earth compound, water, ammonium fluoride is (10-50):(0.005-0.5):(2-35):(0-2):(0.05-0.2):(1-10).

[0023] In some embodiments of the present application, the preparation of NaGdF4 nanocrystals comprises: uniformly stirring oleic acid, ethanol, sodium hydroxide, gadolinium chloride, water, ammonium fluoride and optional europium chloride and terbium chloride, and putting them into a reaction kettle to react at 130℃ for 12 hours to obtain NaGdF4 nanocrystals.

[0024] It should be noted that optional europium chloride and terbium chloride are added during the preparation process, so that the corresponding Eu 3+ ions or Tb 3+NaGdF4 nanocrystals with ions were finally prepared to obtain Eu-doped nanocrystals. 3+ Ionic or doped Tb 3+ Submicron-sized rare-earth silicate phosphors containing ions. The doped rare-earth ions are the luminescent centers.

[0025] The present invention also provides submicron-sized rare earth silicate phosphors prepared by the above preparation method.

[0026] In some embodiments of the present invention, the submicron-sized rare earth silicate phosphor is submicron-sized NaGd9Si6O. 26 Phosphors, whose particle size can be controlled within the range of 500-1000 nm.

[0027] The present invention produces submicron-sized NaGd9Si6O with a narrow particle size distribution. 26 Phosphors have excellent effects when applied to optical devices, including LEDs, optical detectors, or lasers, and can significantly improve the angular color uniformity of display and lighting devices, while also exhibiting good environmental stability.

[0028] This invention provides a submicron-sized rare-earth silicate phosphor and its preparation method. By sintering and then etching a core-shell structured MReF4@SiO2 precursor, ultra-small-sized rare-earth silicate phosphors can be prepared. The particle size of the product can be precisely controlled by sintering temperature and time. Compared with traditional spray pyrolysis, sol-gel, and chemical co-precipitation methods, the preparation method provided by this invention has advantages such as ease of batch production, narrow particle size distribution range, and easy size adjustment. The produced submicron-sized rare-earth silicate phosphor, especially NaGd9Si6O2, is particularly effective. 26 Phosphors can be used in optical devices such as LEDs to significantly improve the angular color uniformity of display and lighting equipment. Attached Figure Description

[0029] Figure 1 Eu provided in Embodiment 1 of the present invention 3+ Doped NaGd9Si6O 26 Schematic diagram of the preparation process of submicron phosphors;

[0030] Figure 2 Eu provided in Embodiment 1 of the present invention 3+ Doped NaGd9Si6O 26 Scanning electron microscope image of submicron phosphor ( Figure 2 A) and particle size range distribution diagram ( Figure 2 (B)

[0031] Figure 3 Eu provided in Embodiment 1 of the present invention 3+Doped NaGd9Si6O 26 Photoluminescence spectrum of sub-micron phosphor;

[0032] Figure 4 Eu provided by the embodiment 1 of the present application 3+ Doped NaGd9Si6O 26 Color coordinate vs. angle of LED assembled by sub-micron phosphor;

[0033] Figure 5 Eu provided by the embodiment 3 of the present application 3+ Doped NaGd9Si6O 26 Scanning electron microscope image (A) and particle size range distribution (B) of sub-micron phosphor; Figure 5 Figure 5

[0034] Figure 6 Eu provided by the embodiment 4 of the present application 3+ Doped NaGd9Si6O 26 Scanning electron microscope image (A) and particle size range distribution (B) of sub-micron phosphor; Figure 6 Figure 6

[0035] Figure 7 Eu provided by the embodiment 5 of the present application 3+ Doped NaGd9Si6O 26 Scanning electron microscope image (A) and particle size range distribution (B) of sub-micron phosphor; Figure 7 Figure 7 DETAILED DESCRIPTION

[0036] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be described clearly and completely below. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0037] If not specifically indicated, the technical means used in the embodiments of the present application are all the conventional means known by those skilled in the art.

[0038] In the following embodiments, if not specifically indicated, the used materials and reagents can be obtained through regular commercial channels.

[0039] Embodiment 1

[0040] The present embodiment provides a Eu 3+ Doped NaGd9Si6O​​​​​​26 The preparation method of the sub-micron fluorescent powder is shown in the following flow chart: Figure 1 The specific steps are as follows:

[0041] 0.4 g of sodium hydroxide, 3 mL of deionized water, 6 mL of ethanol, 5.34 g of oleic acid, 0.25 mmol of gadolinium chloride hydrate, and 0.25 mmol of europium chloride hydrate were mixed uniformly, 2 mmol of ammonium fluoride was added after stirring for 12 hours, and then transferred to a polytetrafluoroethylene reaction kettle for reaction at 130°C for 4 hours. The obtained product was centrifuged and dispersed in n-hexane to form a dispersion liquid with a concentration of 0.1 M. 120 μL of the dispersion liquid was mixed uniformly with 10 mL of cyclohexane, 1 mL of IGEPAL CO-520 (polyoxaethylene (5) nonyl phenyl ether), 150 μL of ammonia water, and 100 μL of tetraethyl silicate, and stirred for 24 hours. The product was precipitated with acetone and centrifuged to obtain the product. The product was calcined at 600°C for 5 minutes and rapidly cooled. It was mixed with a sodium hydroxide solution (concentration of 80 g / L) at room temperature, transferred to a polytetrafluoroethylene reaction kettle for reaction at 180°C for 12 hours. After the reaction, the sample was washed with deionized water and filtered to obtain Eu 3+ ion-doped NaGd9Si6O 26 sub-micron fluorescent powder.

[0042] Figure 2 The Eu 3+ doped NaGd9Si6O 26 sub-micron fluorescent powder obtained in this example is shown in the following scanning electron microscope image and particle size range distribution diagram. As can be seen from the diagram, the fluorescent powder obtained in this example is concentrated around 550 nm.

[0043] Figure 3 The Eu 3+ doped NaGd9Si6O 26 sub-micron fluorescent powder is shown in the following photoluminescence spectrum diagram.

[0044] Figure 4 The LED packaged with the Eu 3+ doped NaGd9Si6O 26 sub-micron fluorescent powder has good environmental stability and lower angle color shift.

[0045] Example 2

[0046] This example provides a Tb 3+ doped NaGd9Si6O 26 sub-micron fluorescent powder, and the steps are as follows:

[0047] NaGd9Si6O:Eu3+was prepared by mixing 0.4 g of sodium hydroxide, 3 mL of deionized water, 6 mL of ethanol, 5.34 g of oleic acid, 0.25 mmol of gadolinium chloride hydrate, and 0.25 mmol of europium chloride hydrate, stirring for 12 hours, adding 2 mmol of ammonium fluoride, and transferring to a polytetrafluoroethylene reaction kettle for reaction at 130 °C for 4 hours. The obtained product was centrifuged and dispersed in n-hexane to form a dispersion liquid with a concentration of 0.1 M. 150 μL of the dispersion liquid was mixed with 10 mL of n-hexane, 1 mL of IGEPAL CO-520, 150 μL of hydrochloric acid, and 50 μL of tetraethyl silicate, and stirred for 24 hours. The product was precipitated with acetone and centrifuged to obtain the product. The product was calcined at 620 °C for 2 minutes and rapidly cooled. The product was mixed with a sodium hydroxide solution (concentration of 120 g / L) at room temperature, transferred to a polytetrafluoroethylene reaction kettle, and reacted at 180 °C for 12 hours. After the reaction, the sample was washed with deionized water and filtered to obtain NaGd9Si6O:Eu3+. 3+ ion-doped NaGd9Si6O 26 submicron fluorescent powder.

[0048] Example 3

[0049] This example provides a Eu 3+ ion-doped NaGd9Si6O 26 submicron fluorescent powder, and a preparation method thereof. The preparation process is shown in Figure 1 , and the specific steps are as follows:

[0050] NaGd9Si6O:Eu3+was prepared by mixing 0.4 g of sodium hydroxide, 3 mL of deionized water, 6 mL of ethanol, 5.34 g of oleic acid, 0.25 mmol of gadolinium chloride hydrate, and 0.25 mmol of europium chloride hydrate, stirring for 12 hours, adding 2 mmol of ammonium fluoride, and transferring to a polytetrafluoroethylene reaction kettle for reaction at 130 °C for 4 hours. The obtained product was centrifuged and dispersed in n-hexane to form a dispersion liquid with a concentration of 0.1 M. 150 μL of the dispersion liquid was mixed with 10 mL of n-hexane, 1 mL of IGEPAL CO-520, 150 μL of hydrochloric acid, and 50 μL of tetraethyl silicate, and stirred for 24 hours. The product was precipitated with acetone and centrifuged to obtain the product. The product was calcined at 620 °C for 2 minutes and rapidly cooled. The product was mixed with a sodium hydroxide solution (concentration of 120 g / L) at room temperature, transferred to a polytetrafluoroethylene reaction kettle, and reacted at 180 °C for 12 hours. After the reaction, the sample was washed with deionized water and filtered to obtain NaGd9Si6O:Eu3+. 3+ ion-doped NaGd9Si6O 26 submicron fluorescent powder.

[0051] The obtained Eu 3+ ion-doped NaGd9Si6O 26The scanning electron microscope image and the particle size range distribution diagram of the submicron fluorescent powder are shown in Figure 5

[0052] Example 4

[0053] This example provides a Eu 3+ doped NaGd9Si6O 26 doped NaGd9Si6O

[0054] The 0.6 g of sodium hydroxide, 2 mL of deionized water, 8 mL of ethanol, 10 g of oleic acid, 0.25 mmol of gadolinium chloride hydrate, and 0.25 mmol of europium chloride hydrate were mixed uniformly, 2 mmol of ammonium fluoride was added after stirring for 12 hours, and then transferred to a polytetrafluoroethylene reactor for reaction at 130°C for 4 hours. The obtained product was centrifuged and dispersed in n-hexane to form a dispersion liquid with a concentration of 0.1 M. 120 μL of the dispersion liquid was mixed uniformly with 10 mL of cyclohexane, 1 mL of IGEPAL CO-520, 200 μL of hydrochloric acid, and 150 μL of tetraethyl silicate, and stirred for 24 hours. The product was precipitated with acetone and centrifuged to obtain the product. The product was calcined at 800°C for 5 minutes and rapidly cooled. It was mixed with a sodium hydroxide solution (concentration of 80 g / L) at room temperature, transferred to a polytetrafluoroethylene reactor for reaction at 180°C for 12 hours. After the reaction, the sample was washed with deionized water and filtered to obtain the Eu 3+ doped NaGd9Si6O 26 submicron fluorescent powder.

[0055] The obtained Eu 3+ doped NaGd9Si6O 26 submicron fluorescent powder. Figure 6

[0056] Example 5

[0057] This example provides a Eu 3+ doped NaGd9Si6O 26 submicron fluorescent powder. Figure 1

[0058] ​​​0.4 g of sodium hydroxide, 3 mL of deionized water, 6 mL of ethanol, 5.34 g of oleic acid, 0.25 mmol of gadolinium chloride hydrate, and 0.25 mmol of europium chloride hydrate were mixed uniformly, 2 mmol of ammonium fluoride was added after stirring for 12 hours, and the mixture was transferred to a polytetrafluoroethylene reaction kettle for reaction at 130°C for 4 hours. The obtained product was centrifuged and dispersed in n-hexane to form a dispersion liquid with a concentration of 0.1 M. 120 μL of the dispersion liquid was mixed uniformly with 10 mL of cyclohexane, 1 mL of IGEPAL CO-520 (polyoxaethylene (5) nonyl phenyl ether), 150 μL of ammonia water, and 100 μL of tetraethyl silicate, and stirred for 24 hours. The product was precipitated with acetone and centrifuged to obtain the product. The product was calcined at 900°C for 5 minutes and rapidly cooled. The product was mixed with a sodium hydroxide solution (concentration of 80 g / L) at room temperature, and transferred to a polytetrafluoroethylene reaction kettle for reaction at 180°C for 12 hours. After the reaction, the sample was washed with deionized water and filtered to obtain Eu 3+ ion-doped NaGd9Si6O 26 submicron phosphor.

[0059] The obtained Eu 3+ ion-doped NaGd9Si6O 26 submicron phosphor. Figure 7 The scanning electron microscope image and the particle size range distribution diagram of the obtained Eu

[0060] As can be seen from Figure 2 and Figures 5-7 , for the Eu 3+ ion-doped NaGd9Si6O 26 submicron phosphor, as the sintering temperature increases, the particle size becomes larger, and the particle size distribution becomes less concentrated.

[0061] Example 6

[0062] This example provides a preparation method of Eu 3+ ion-doped NaLu9Si6O 26 submicron phosphor, and the specific steps are as follows:

[0063] 0.4 g of sodium hydroxide, 3 mL of deionized water, 6 mL of ethanol, 5.34 g of oleic acid, 0.25 mmol of lutetium chloride hydrate, and 0.25 mmol of europium chloride hydrate were mixed uniformly, 2 mmol of ammonium fluoride was added after stirring for 12 hours, and the mixture was transferred to a polytetrafluoroethylene reaction kettle for reaction at 130°C for 4 hours. The obtained product was centrifuged and dispersed in n-hexane to form a dispersion liquid with a concentration of 0.1 M. 120 μL of the dispersion liquid was mixed uniformly with 10 mL of cyclohexane, 1 mL of IGEPAL CO-520, 150 μL of ammonia water, and 100 μL of tetraethyl orthosilicate, and stirred for 24 hours. The product was precipitated with acetone and centrifuged to obtain the product. The product was calcined at 600°C for 5 minutes and rapidly cooled. The product was mixed with a sodium hydroxide solution (concentration: 80 g / L) at room temperature, and transferred to a polytetrafluoroethylene reaction kettle for reaction at 180°C for 12 hours. After the reaction, the sample was washed with deionized water and filtered to obtain Eu 3+ ion-doped NaLu9Si6O 26 submicron-sized fluorescent powder.

[0064] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and are not intended to limit the same; although the present application has been described in detail with reference to the foregoing examples, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing examples, or make equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing submicron-sized rare earth silicate phosphors, characterized in that, include: MReF4@SiO2 precursor with a core-shell structure is formed by coating MReF4 nanocrystals with silica. After sintering the precursor, silica is etched with alkaline solution to obtain the submicron-sized rare earth silicate phosphor. Where M represents an alkali metal and Re represents a lanthanide rare earth element.

2. The method for preparing submicron-sized rare earth silicate phosphor according to claim 1, characterized in that, M is Li, Na, or K, and Re is lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, or lutetium.

3. The method for preparing submicron-sized rare earth silicate phosphor according to claim 1 or 2, characterized in that, The preparation of the precursor includes: reacting MReF4 nanocrystals with a surfactant, cyclohexane, n-hexane, ammonia, hydrochloric acid and tetraethyl silicate, followed by precipitation with ethanol and acetone.

4. The method for preparing submicron-sized rare earth silicate phosphor according to claim 3, characterized in that, The surfactant is one or more of IGEPAL CA-630, IGEPALCA-720, IGEPALCA-730, IGEPAL CO-520, and IGEPAL CO-890; And / or, the volume ratio of the surfactant, cyclohexane, n-hexane, ammonia, hydrochloric acid and tetraethyl silicate is (0.05-10):(0-30):(0-30):(0-0.2):(0-0.2):(0.002-1).

5. The method for preparing submicron-sized rare earth silicate phosphor according to claim 1 or 2, characterized in that, The sintering temperature is 500-1200℃.

6. The method for preparing submicron-sized rare earth silicate phosphor according to claim 1 or 2, characterized in that, The sintering process involves sintering at 600-700℃ for 1-5 minutes.

7. The method for preparing submicron-sized rare earth silicate phosphor according to claim 1 or 2, characterized in that, The alkaline solution is a sodium hydroxide solution with a concentration of 20-200 g / L.

8. The method for preparing submicron-sized rare earth silicate phosphor according to claim 7, characterized in that, The reaction temperature for etching silicon dioxide with sodium hydroxide solution is 170-190℃.

9. A submicron-sized rare earth silicate phosphor, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

10. The submicron-sized rare earth silicate phosphor according to claim 9, characterized in that, The submicron-sized rare earth silicate phosphor is submicron-sized NaGd9Si6O 26 Phosphors have a particle size in the range of 500-1000 nm.

11. The submicron-sized NaGd9Si6O as described in claim 10 26 The application of phosphors in optical devices, including LEDs, optical detectors, or lasers.

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