A red europium-doped fluorapatite fluorescent powder and a preparation method thereof

Abstract

The application discloses europium-doped apatite-based red fluorescent powder and a preparation method thereof, and relates to the technical field of luminescent materials. 10‑x (PO4)6F2:xEu 3+ ; wherein x is Eu 3+ doping substitution Ca 2+ , and the molar ratio of Eu 3+ is 0.02<=x<=0.2. The preparation method mainly uses a calcium source, a fluorine source, a phosphate, and an Eu 3+ containing compound as raw materials, and the fluorescent powder can be obtained through hydrothermal heating at a temperature of 150-250 DEG C, cleaning and drying. The prepared fluorescent powder shows strong narrow-band red emission under excitation of ultraviolet light of 390 nm, the emission wavelength ranges from 579 nm to 696 nm, and the main peak is at 618 nm; the color temperature is 2138.74 K, and the color coordinates are about (0.5896, 0.3385), so the prepared fluorescent powder can be used as a red fluorescent powder with relatively good thermal stability. The preparation process is simple, green and environmentally friendly, and is convenient for large-scale production.

Description

Technical Field

[0001] This invention relates to the field of luminescent materials technology, and in particular to a method for preparing europium-doped fluoroapatite red phosphor and its application. Background Technology

[0002] LED lighting is a lighting technology that converts electrical energy into light energy based on semiconductor chips. It boasts advantages such as high conversion efficiency, long lifespan, environmental friendliness, adjustable light intensity, and rich colors. Currently, white LEDs are mainly used in solid-state lighting. Their specific principle involves combining blue light with a wavelength of 460nm with YAG:CeO, a semiconductor material that can convert some of the blue light into yellow light. 3+ It is obtained by combining phosphors. However, blue light chips excite YAG:Ce 3+ Phosphors produce white light with issues such as high color temperature, low color rendering index, and poor color reproduction. Therefore, developing a high-performance red phosphor to achieve white LEDs with low correlated color temperature and high color rendering index is of great significance.

[0003] Currently, the main red fluorescent powder is Eu. 2+ Doping with nitrides, nitrogen oxides or sulfides and Mn 4+ Primarily composed of fluoride-doped phosphors. Eu 2+ Nitride-doped phosphors offer a rich variety of emission colors, high luminous efficiency, and low thermal quenching performance. However, nitride-based phosphors require high temperature, high pressure, and inert gas conditions for preparation, resulting in high costs. Furthermore, they exhibit a wide stimulated emission band and severe photon reabsorption in the green and yellow regions, leading to a reduction in the short-wavelength components of white LEDs. 2+ Sulfide doping exhibits high luminescence efficiency and good temperature stability; however, the presence of the sulfide matrix can generate harmful substances during the preparation process, making it environmentally unfriendly. Mn 4+ Fluoride-doped compounds exhibit weak luminescence intensity and poor thermal stability, and Mn 4+ Mn exhibits relatively poor chemical stability in fluorides, particularly in humid environments. 4+ It is easily hydrolyzed into manganese oxides and hydroxides, which leads to a decrease in the luminous efficiency of the phosphor. Therefore, there is a need to develop an environmentally friendly, low-cost, optically superior, and simple-to-produce red phosphor. Summary of the Invention:

[0004] The purpose of this invention is to provide a europium-doped fluoroapatite and its preparation method. The phosphor is environmentally friendly, low-cost, has excellent optical properties, and is simple to prepare. It is produced under ultraviolet to blue light excitation using Eu... 3+Europium-doped fluorapatite exhibits strong narrow-band red emission within its crystal lattice, with an emission wavelength range of 579–696 nm and a main peak at 618 nm. Calculations show that its color temperature remains at 2138.74 K, its color purity is 86.95%, and its thermal quenching activation energy is 0.276 eV, indicating that europium-doped fluorapatite is a red phosphor with high color saturation, good thermal stability, and excellent fluorescence intensity.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A europium-doped apatite-based red phosphor with the chemical formula Ca 10-x Eu x (PO4)6F2, where the activator is Eu 3 + , 0.02≤x≤0.2.

[0007] A method for preparing europium-doped fluoroapatite red phosphor includes the following steps:

[0008] Step 1: Weigh out the raw materials containing Ca and Eu and hexadecyltrimethylammonium bromide according to the stoichiometric ratio and mix them evenly to form solution A. Weigh out the raw materials containing F and PO4 and sodium citrate and mix them evenly to form solution B.

[0009] Step 2: Add solution B dropwise into solution A and stir until well mixed;

[0010] Step 3: Pour the mixed solution into the reaction vessel, heat, cool, and then clean and dry;

[0011] Preferably, the stoichiometric ratio of Ca, Eu, F, PO4, hexadecyltrimethylammonium bromide, and sodium citrate is 0.37:1:0.41:0.11:1.

[0012] Preferably, the Ca-containing compound is any one or a combination of at least two of calcium chloride, calcium nitrate, calcium acetate, calcium sulfate, and calcium bicarbonate.

[0013] Preferably, the F-containing compound is a soluble fluoride such as sodium fluoride, potassium fluoride, ammonium fluoride, lithium fluoride, or ammonium hydrogen fluoride.

[0014] Preferably, the phosphate is a soluble phosphate such as potassium dihydrogen phosphate, sodium dihydrogen phosphate, sodium tripolyphosphate, sodium pyrophosphate, or sodium hexametaphosphate.

[0015] Preferably, the stirring method is magnetic stirring, the stirring speed is 500±50 r / min, and the stirring time is 50 to 120 minutes.

[0016] Preferably, the heating device can be an oven, the heating container can be a reaction vessel, and the heating temperature is 150 to 250°C.

[0017] Preferably, the cleaning solvent is deionized water and anhydrous ethanol.

[0018] The beneficial effects of this invention are:

[0019] 1. The phosphor prepared by this invention can be effectively excited in the 200-480nm wavelength range, with an emission wavelength range of 575-700nm and a main peak located at 600-630nm.

[0020] 2. The phosphor prepared by this invention has good resistance to thermal quenching, and the fluorescence intensity of the main emission peak at 448K can still maintain about 80% of the initial value.

[0021] 3. The phosphor prepared by this invention has excellent physicochemical stability, and because it is an apatite-based phosphor, it is very environmentally friendly. Attached Figure Description

[0022] Figure 1 The Ca prepared in Example 1 0.92 Eu 0.08 X-ray diffraction pattern of (PO4)6F2 sample.

[0023] Figure 2 The Ca prepared in Example 1 0.92 Eu 0.08 Scanning electron micrograph of (PO4)6F2 sample.

[0024] Figure 3 The Ca prepared in Example 1 0.92 Eu 0.08 Photoluminescence spectrum of (PO4)6F2 sample.

[0025] Figure 4 The Ca prepared in Example 2 0.9 Eu 0.1 X-ray diffraction pattern of (PO4)6F2 sample.

[0026] Figure 5 The Ca prepared in Example 1 0.9 Eu 0.1 Scanning electron micrograph of (PO4)6F2 sample.

[0027] Figure 6 The Ca prepared in Example 2 0.9 Eu 0.1 Photoluminescence spectrum of (PO4)6F2 sample.

[0028] Figure 7 The Ca prepared in Example 3 0.88 Eu0.12 X-ray diffraction pattern of (PO4)6F2 sample.

[0029] Figure 8 The Ca prepared in Example 1 0.88 Eu 0.12 Scanning electron micrograph of (PO4)6F2 sample.

[0030] Figure 9 The Ca prepared in Example 3 0.88 Eu 0.12 Photoluminescence spectrum of (PO4)6F2 sample. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be noted that these embodiments are for illustrative purposes only and do not limit the scope of the invention.

[0032] Example 1

[0033] Preparation of Ca 0.92 Eu 0.08 (PO4)6F2 sample: First, 81.09 g of Ca(NO3)2·4H2O, 13.2 g of Eu(NO3)3, and 40.2 g of hexadecyltrimethylammonium bromide were mixed thoroughly into 500 mL of deionized water to form solution A. Then, 41.99 g of NaF, 54.14 g of (NH4)2HPO4, and 25.8 g of Na3Cit were mixed thoroughly into 500 mL of deionized water solution B. Next, solution B was added dropwise to solution A at a rate of 10 drops per minute, while simultaneously stirring with a magnetic stirrer at 500 rpm for 30 minutes. The mixture was then transferred to a reaction vessel and placed in an oven, heated to 180°C for 12 hours. Finally, the resulting powder was washed twice with anhydrous ethanol and then twice with deionized water, and then dried in a vacuum drying oven at 80°C to obtain Ca. 0.92 Eu 0.08 (PO4)6F2 crystal.

[0034] The Ca obtained during preparation 0.92 Eu 0.08 X-ray diffraction analysis of (PO4)6F2 crystals, such as Figure 1 As shown, the XRD diffraction peaks of the obtained powder crystals correspond perfectly to the pure fluorapatite phase, with no impurity peaks appearing, indicating that the prepared sample is a pure phase. Furthermore, scanning electron microscopy analysis was performed on the experimental sample to determine its microstructure. Figure 2The obtained particles exhibit a rod-like morphology, with an average length of approximately 3-4 μm and an average diameter of approximately 1-2 μm. Under excitation at 250 μm, the emission spectrum of the sample powder is as follows: Figure 3 As shown, five diffraction peaks appear in the 575 to 750 nm band, corresponding to... 5 D0→ 7 F0、 5 D0→ 7 F1 5 D0→ 7 F2 5 D0→ 7 F3 5 D0→ 7 The F4 transition ultimately indicates that the fluorescence emits red light.

[0035] Example 2

[0036] Preparation of Ca 0.9 Eu 0.1 (PO4)6F2 sample: First, 79.31 g of Ca(NO3)2·4H2O, 16.5 g of Eu(NO3)3, and 40.2 g of hexadecyltrimethylammonium bromide were mixed evenly into 500 mL of deionized water to form solution A; 41.99 g of NaF, 54.14 g of (NH4)2HPO4, and 25.8 g of Na3Cit were mixed evenly into 500 mL of deionized water solution B. Next, solution B was added dropwise to solution A at a rate of 10 drops per minute, while stirring with a magnetic stirrer at 500 rpm for 30 minutes; the mixture was then transferred to a reaction vessel and placed in an oven, heated to 180°C for 12 hours. Finally, the resulting powder was washed twice with anhydrous ethanol and then twice with deionized water, and then dried in a vacuum drying oven at 80°C to obtain Ca. 0.9 Eu 0.1 (PO4)6F2 crystal.

[0037] The Ca obtained during preparation 0.9 Eu 0.1 X-ray diffraction analysis of (PO4)6F2 crystals, such as Figure 4 As shown, the XRD diffraction peaks of the obtained powder crystals correspond perfectly to the pure fluorapatite phase, with no impurity peaks appearing, indicating that the prepared sample is a pure phase. Furthermore, scanning electron microscopy analysis was performed on the experimental sample to determine its microstructure. Figure 5 The obtained particles exhibit a rod-like morphology, with an average length of approximately 3-4 μm and an average diameter of approximately 1-2 μm. Under excitation at 250 μm, the emission spectrum of the sample powder is as follows: Figure 6 As shown, five diffraction peaks appear in the 575 to 750 nm band, corresponding to... 5 D0→7 F0、 5 D0→ 7 F1 5 D0→ 7 F2 5 D0→ 7 F3 5 D0→ 7 The F4 transition ultimately indicates that the fluorescence emits red light.

[0038] Example 3

[0039] Preparation of Ca 0.88 Eu 0.12 (PO4)6F2 sample: First, 77.55g of Ca(NO3)2·4H2O, 19.8g of Eu(NO3)3, and 40.2g of hexadecyltrimethylammonium bromide were mixed evenly into 500mL of deionized water to form solution A; 41.99g of NaF, 54.14g of (NH4)2HPO4, and 25.8g of Na3Cit were mixed evenly into 500mL of deionized water solution B. Next, solution B was added dropwise to solution A at a rate of 10 drops per minute, while stirring with a magnetic stirrer at 500 rpm for 30 minutes; the mixture was then transferred to a reaction vessel and placed in an oven, heated to 180℃ for 12 hours. Finally, the resulting powder was washed twice with anhydrous ethanol and then twice with deionized water, and then dried in a vacuum drying oven at 80℃ to obtain Ca. 0.88 Eu 0.12 (PO4)6F2 crystal.

[0040] The Ca obtained during preparation 0.88 Eu 0.12 X-ray diffraction analysis of (PO4)6F2 crystals, such as Figure 7 As shown, the XRD diffraction peaks of the obtained powder crystals correspond perfectly to the pure fluorapatite phase, with no impurity peaks appearing, indicating that the prepared sample is a pure phase. Furthermore, scanning electron microscopy analysis was performed on the experimental sample to determine its microstructure. Figure 8 The obtained particles exhibit a rod-like morphology, with an average length of approximately 3-4 μm and an average diameter of approximately 1-2 μm. Under excitation at 250 μm, the emission spectrum of the sample powder is as follows: Figure 9 As shown, five diffraction peaks appear in the 575 to 750 nm band, corresponding to... 5 D0→ 7 F0、 5 D0→ 7 F1 5 D0→ 7 F2 5 D0→ 7 F3 5D0→ 7 The F4 transition ultimately indicates that the fluorescence emits red light.

Claims

1. A europium-doped apatite-based red phosphor, characterized in that, The general formula of the apatite-based phosphor is Ca 10- x Eu x (PO4)6F2, where: The matrix is ​​Ca 10 (PO4)6F2, activator is Eu 3+ It is through Eu 3+ Obtained by replacing cations in the matrix; 0.02≤x≤0.2； The phosphor Ca 10-x Eu x (PO4)6F2 was prepared by hydrothermal synthesis. The preparation method, employing a hydrothermal synthesis method, is characterized by comprising the following steps: Step 1: Weigh the calcium source, hexadecyltrimethylammonium bromide, and Eu-containing reagents according to the stoichiometric ratio. 3+ The compounds are mixed evenly to form solution A. The corresponding amounts of sodium citrate, fluoride, and phosphate are weighed and mixed evenly to form solution B. Step 2: Add solution B to solution A and stir until well mixed; Step 3: Load the mixed solution into the reaction vessel, heat it, cool it, and then clean and dry it. In step 1, the stoichiometric ratio of Ca, Eu, F, PO4, hexadecyltrimethylammonium bromide, and sodium citrate is 0.37:1:0.41:0.11:

1.

2. The europium-doped apatite-based red phosphor as described in claim 1, characterized in that, In step 1, the calcium source includes one or more of calcium chloride, calcium nitrate, calcium acetate, calcium sulfate, or calcium bicarbonate; containing Eu. 3+ The compounds include one or more of europium nitrate or europium acetate; fluorides include one or more of sodium fluoride, potassium fluoride, ammonium fluoride, lithium fluoride, or ammonium hydrogen fluoride; phosphates include one or more of potassium dihydrogen phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium tripolyphosphate, sodium pyrophosphate, and sodium hexametaphosphate.

3. The europium-doped apatite-based red phosphor as described in claim 1, characterized in that, In step 2, solution B is added to solution A by dropwise addition.

4. The europium-doped apatite-based red phosphor as described in claim 1, characterized in that, In step 2, the stirring method is magnetic stirring, the stirring speed is 500±50 r / min, and the stirring time is 50 to 120 minutes.

5. The europium-doped apatite-based red phosphor as described in claim 1, characterized in that, In step 3, the reactor is heated for 5 to 10 hours at a temperature of 150 to 250 °C.

6. The europium-doped apatite-based red phosphor as described in claim 1, characterized in that, In step 3, the cleaning solvent is deionized water and anhydrous ethanol.

7. The europium-doped apatite-based red phosphor as described in claim 1, characterized in that, The excitation spectrum ranges from 200 to 480 nm, the emission spectrum ranges from 575 to 700 nm, the main emission peak is located in the range of 600 to 630 nm, and the emitted light is red.

8. The europium-doped apatite-based red phosphor as described in claim 1, characterized in that, Eu 3+ Apatite-doped phosphors are used in solid-state lighting and display applications.

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