Cationic vacancy type garnet near-infrared phosphor and preparation method thereof

Abstract

The present invention discloses a cation vacancy type garnet near-infrared phosphor, the chemical formula of which is: Ca 3‑x‑y Eu x Sc 2‑z SiO 12 , where 0

Description

Technical Field

[0001] The invention relates to phosphor and a preparation method thereof, in particular to a cation vacancy type garnet near-infrared phosphor and a preparation method thereof. Background Art

[0002] Near-infrared spectroscopy (700-1000nm) technology plays an important role in non-destructive testing of agricultural products, biological imaging, night vision, plant cultivation, and other fields. However, due to shortcomings such as low luminous efficiency, poor thermal stability, and narrow-band emission, it cannot meet the requirements of commercial applications.

[0003] Currently, by the transition metal ions (Cr 3+ 、Mn 4+ etc.) or rare earth ions (Eu 3+ 、Tm 3+ However, the emission peak width of rare earth ions with 4f-4f transition is not wide enough (full width at half maximum < 50nm), and the absorption area is also very weak, which cannot meet the needs of large-scale detection. 4 T2→ 4 A2 transition Cr 3+ Luminescence is considered an ideal near-infrared luminescence center. It exhibits broadband emission in the 650-1200nm range. However, its low luminescence efficiency and poor thermal stability have seriously hindered its commercial application. Therefore, the development of broadband near-infrared phosphors with high luminescence efficiency and good thermal stability has attracted widespread attention from scholars.

[0004] Eu 2+ As an important rare earth ion activator, it has 4f-5d transition, broad absorption and broadband emission. 2+ Most activated near-infrared phosphors are nitrides or nitrogen oxides, but their preparation process is very demanding, resulting in high manufacturing costs that limit their application in near-infrared LEDs. Therefore, in recent years, scholars have shifted their attention to Eu 2+ The activated oxide phosphor has a simple preparation process and does not require a high temperature and high pressure environment, thereby reducing manufacturing costs and improving yield. 2+Activated oxide phosphors mainly include yttrium, silicate, gallate (Advanced Functional Materials. 32 (2022), 2103927; Journal of Materials Chemistry C. 56 (2020) 4644-4647; Advanced Optical Materials. 9(2021), 2100131), etc. However, these phosphors rarely achieve near-infrared emission. Among oxides, garnet structure has been widely studied due to its unique luminescence tunable properties and is considered to be able to achieve Eu 2+ Activated broadband near-infrared emitting phosphors are ideal host materials, but existing phosphors have the disadvantages of low luminous efficiency and poor thermal stability. Summary of the Invention

[0005] Purpose of the invention: In order to overcome the deficiencies in the prior art, the present invention aims to provide a cation vacancy type garnet near-infrared phosphor. Another purpose of the present invention is to provide a method for preparing the cation vacancy type garnet near-infrared phosphor.

[0006] Technical solution: The present invention discloses a cation vacancy type garnet near-infrared phosphor, the chemical formula of which is: Ca 3-x-y Eu x Sc 2-z SiO 12 , where 0 <x≤0.08,0<y≤0.2,0≤z≤0.25。

[0007] Preferably, 0.02≤x≤0.08, 0 <y≤0.2,0≤z≤0.25。

[0008] The preparation method of the cationic vacancy type garnet near-infrared phosphor comprises the following steps:

[0009] S1. Weigh the Ca raw material, Eu raw material, Sc raw material, and Si raw material according to the stoichiometric ratio and grind them for 30-40 minutes, adding anhydrous ethanol in small amounts several times during the process;

[0010] S2. Transfer the evenly ground powder mixture into an alumina crucible and slightly shake the crucible to spread the powder evenly in the crucible;

[0011] S3. Place the crucible in a high-temperature horizontal tube furnace, first raise the temperature to 1400-1600°C in air, keep the temperature, then cool it to 1000-1200°C, and anneal it in a reducing atmosphere;

[0012] S4, after cooling to room temperature, grinding again to obtain a cation vacancy type garnet near-infrared phosphor.

[0013] Furthermore, the Ca raw material is CaCO3 powder with a purity of 99.9%. The Eu raw material is Eu2O3 powder with a purity of 99.99%. The Sc raw material is Sc2O3 powder, which is analytically pure (99.99%). The Si raw material is nano-SiO2 powder with a particle size of 45-55nm and a purity of 99.5%.

[0014] Furthermore, in step S1, anhydrous ethanol is added in 1 to 4 times, and the amount added each time accounts for 2% to 6% of the total mass of the powder.

[0015] Furthermore, in step S3, the heating rate is 3-5°C / min, the holding time is 2-6 hours, and the cooling rate is 3-5°C / min. The reducing atmosphere is a mixture of N2 and H2, with the volume percentage of H2 being 10-20%.

[0016] Preparation principle: It is synthesized by high temperature solid phase method, and annealing treatment is carried out during the process, which greatly promotes the 3+ to Eu 2 + Reduction, improve Eu in the material 2+ The content of Eu 2+ It occupies the lattice of the eight-coordinated dodecahedron CaO8 in the crystal lattice and becomes a luminescence center, which can be effectively excited by green light and emit near-infrared light. 2+ ions or Sc 3+ The content of ions is controlled by introducing vacancy defects in the matrix, regulating the local structure and forming electron capture centers, further improving the luminescence efficiency and thermal stability.

[0017] Beneficial effects: Compared with the prior art, the present invention has the following significant features:

[0018] 1. The obtained cationic vacancy type garnet near-infrared phosphor uses garnet structure silicate as the matrix and Eu 2+ It is the luminescence center, showing strong absorption in the range of 450-800nm, and has a good match with the green light chip. It can be used in near-infrared LEDs with high luminous efficiency and good thermal stability.

[0019] 2. The obtained phosphor exhibits broad emission in the near-infrared region of 700-1300nm, with an emission peak at 840nm. The manufactured near-infrared LED can well meet the needs of food non-destructive testing, biological imaging and other fields;

[0020] 3. The obtained phosphor adopts a defect control strategy, the luminescence intensity is significantly improved, and it exhibits reverse thermal quenching phenomenon and excellent thermal stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1The Ca obtained in Example 1 2.98 Eu 0.02 Sc 1.95 SiO 12 The excitation spectrum of the phosphor with 840 nm as the monitoring wavelength and the emission spectrum with 520 nm as the excitation wavelength, the horizontal axis is the wavelength (nm) and the vertical axis is the relative luminous intensity.

[0022] Figure 2 Example 2 obtained Ca 2.78 Eu 0.02 Sc2Si3O 12 The emission intensity of the phosphor is comparable to that of the existing Ca 2.98 Eu 0.02 Sc2Si3O 12 Comparison of phosphor emission intensity, the coordinate is wavelength (nm) and the vertical axis is relative luminous intensity.

[0023] Figure 3 The Ca obtained in Example 3 2.92 Eu 0.08 Sc 1.85 SiO 12 Photo of non-destructive testing of fruit after the phosphor is encapsulated into a near-infrared device.

[0024] Figure 4 The Ca obtained in Example 4 2.98 Eu 0.02 Sc 1.75 SiO 12 Normalized emission intensity of phosphor at different temperatures, the horizontal axis is temperature (K), and the vertical axis is normalized intensity. DETAILED DESCRIPTION

[0025] In the following examples, the raw materials and devices used were purchased.

[0026] Eu synthesized by high temperature solid phase method 2+ The formulas of four specific examples of the doped garnet structure near-infrared phosphor are shown in Table 1. In the following examples, the amount of anhydrous ethanol added is 1 time / 0.75 ml, 3 times / 0.4 ml, 2 times / 0.5 ml, and 4 times / 0.25 ml, respectively.

[0027] Table 1 Ingredients of Examples 1 to 4

[0028]

[0029] Example 1

[0030] A cation vacancy type garnet near-infrared phosphor (Ca 2.97 Eu 0.02 Sc 1.95 SiO12 ), comprising the following steps:

[0031] S1. Weigh the raw materials according to the composition in Table 1, put them into an agate grinding mortar and grind them for 30 minutes, adding 0.75 ml of anhydrous ethanol once during the grinding process;

[0032] S2. Transfer the evenly ground powder mixture into an alumina crucible and slightly shake the crucible to spread the powder evenly in the crucible;

[0033] S3. Place the crucible in a high-temperature horizontal tube furnace, first heat it to 1450°C in air at a rate of 5°C / min, and keep it at that temperature for 2 hours, then cool it to 1000°C at a rate of 3°C / min, and anneal it in a reducing atmosphere of N2-H2 (10%) for 2 hours;

[0034] S4. After cooling to room temperature, grinding again can obtain cationic vacancy type garnet near-infrared phosphor.

[0035] The test results are as follows:

[0036] The obtained powder samples were subjected to fluorescence spectroscopy (Hitachi F-4600, Japan). The excitation spectrum was measured at 840 nm as the monitoring wavelength, and the emission spectrum was measured at 520 nm as the excitation wavelength. The test results are shown in Figure 1 .Depend on Figure 1 It can be seen that the prepared phosphor exhibits broadband emission in the range of 700-1300 nm, with a full width at half maximum (FWHM) of 181 nm.

[0037] Example 2

[0038] A cation vacancy type garnet near-infrared phosphor (Ca 2.78 Eu 0.02 Sc2Si3O 12 ) comprising the following steps:

[0039] S1. Weigh the raw materials according to the composition in Table 1, put them into an agate grinding mortar and grind them for 35 minutes. During this period, add anhydrous ethanol three times, each time adding 0.4 ml;

[0040] S2. Transfer the evenly ground powder mixture into an alumina crucible and slightly shake the crucible to spread the powder evenly in the crucible;

[0041] S3. Place the crucible in a high-temperature horizontal tube furnace, heat it to 1400°C in air at a rate of 3°C / min, and keep it at that temperature for 6 hours. Then cool it to 1150°C at a rate of 5°C / min, and anneal it in a reducing atmosphere of N2-H2 (20%) for 3 hours.

[0042] S4. After cooling to room temperature, grinding again can obtain cationic vacancy type garnet near-infrared phosphor.

[0043] The test results are as follows:

[0044] The obtained powder samples were subjected to fluorescence spectroscopy (Hitachi F-4600, Japan). The excitation spectrum was measured at 840 nm as the monitoring wavelength, and the emission spectrum was measured at 520 nm as the excitation wavelength. The test results are shown in Figure 2 .Depend on Figure 2 It can be seen that the emission intensity of the phosphor provided by the present invention is increased by 2.04 times.

[0045] Example 3

[0046] A cation vacancy type garnet near-infrared phosphor (Ca 2.92 Eu 0.08 Sc 1.85 SiO 12 ) comprising the following steps:

[0047] S1. Weigh the raw materials according to the composition in Table 1, put them into an agate grinding mortar and grind them for 30 minutes. During this period, add anhydrous ethanol twice, each time adding 0.5 ml;

[0048] S2. Transfer the evenly ground powder mixture into an alumina crucible and slightly shake the crucible to spread the powder evenly in the crucible;

[0049] S3. Place the crucible in a high-temperature horizontal tube furnace, heat it to 1500°C in air at a rate of 5°C / min, and keep it at that temperature for 5 hours. Then cool it to 1100°C at a rate of 4°C / min, and anneal it in a reducing atmosphere of N2-H2 (10%) for 4 hours.

[0050] S4. After cooling to room temperature, grinding again can obtain cationic vacancy type garnet near-infrared phosphor.

[0051] The application results are as follows:

[0052] The obtained powder was coated onto a 520 nm chip and packaged into a near-infrared LED for non-destructive testing of fruits. The test results are shown in Figure 3 .Depend on Figure 3 It can be seen that the packaged near-infrared LED can accurately detect the spoiled parts of the fruit.

[0053] Example 4

[0054] A cation vacancy type garnet near-infrared phosphor (Ca 2.97 Eu 0.02 Sc 1.75 SiO 12) comprising the following steps:

[0055] S1. Weigh the raw materials according to the composition in Table 1, put them into an agate grinding mortar and grind them for 40 minutes. During this period, add anhydrous ethanol four times, each time adding 0.25 ml;

[0056] S2. Transfer the evenly ground powder mixture into an alumina crucible and slightly shake the crucible to spread the powder evenly in the crucible;

[0057] S3. Place the crucible in a high-temperature horizontal tube furnace, heat it to 1600°C in air at a rate of 5°C / min, and keep it at that temperature for 4 hours. Then cool it to 1200°C at a rate of 5°C / min, and anneal it in a reducing atmosphere of N2-H2 (15%) for 3.5 hours.

[0058] S4. After cooling to room temperature, grinding again can obtain cationic vacancy type garnet near-infrared phosphor.

[0059] The test results are as follows:

[0060] The obtained powder samples were subjected to variable temperature fluorescence tests, and the emission spectra at 298 K, 323 K, 348 K, 373 K, 398 K, 423 K and 448 K were tested respectively. The test results are shown in Figure 4 .Depend on Figure 4 It can be seen that the phosphor provided by the present invention has excellent thermal stability and exhibits an anti-thermal quenching phenomenon, and the emission intensity at 448K is 117% of that at room temperature.

[0061] Among the above embodiments, embodiment 2 is the best embodiment.

[0062] Comparative Example 1

[0063] The remaining steps of this embodiment are the same as those of embodiment 1, except that annealing for 2 hours is replaced by annealing for 1 hour. Fluorescence spectrum test (Hitachi F-4600, Japan) was performed, and the results showed that Eu 3+ Almost not reduced to Eu 2+ .

[0064] Comparative Example 2

[0065] The remaining steps of this embodiment are the same as those of embodiment 3, with the only difference being that the reducing atmosphere is replaced by H2 with a volume percentage of 5%. Fluorescence spectroscopy (Hitachi F-4600, Japan) was performed and the results showed that the spectrum showed Eu 3+ Characteristic narrowband emission, no Eu 2+ broadband transmission.

[0066] Comparative Example 3

[0067] The remaining steps of this example were the same as those of Example 4, with the only difference being that the 4-hour incubation was replaced by a 1-hour incubation. Fluorescence spectroscopy (Hitachi F-4600, Japan) was performed, and the results showed that the thermal stability was significantly deteriorated.

Claims

1. A cationic vacancy type garnet near-infrared phosphor, characterized in that: The chemical formula is: Ca 3-x-y Eu x Sc 2- z SiO 12 , where 0 <x≤0.08,0<y≤0.2,0≤z≤0.25。 2. The cationic vacancy type garnet near-infrared phosphor according to claim 1, characterized in that: 0.02≤x≤0.08,0 <y≤0.2,0≤z≤0.25。 3. The method for preparing a cationic vacancy type garnet near-infrared phosphor according to claim 1 or 2, characterized in that: The following steps are involved: S1. Weigh the Ca raw material, Eu raw material, Sc raw material, and Si raw material according to the stoichiometric ratio and grind them for 30-40 minutes, adding anhydrous ethanol in small amounts several times during the process; S2. Transfer the evenly ground powder mixture into a crucible and slightly shake the crucible to spread the powder evenly in the crucible; S3. Place the crucible in a high-temperature horizontal tube furnace, first raise the temperature to 1400-1600°C in air, keep the temperature, then cool it to 1000-1200°C, and anneal it in a reducing atmosphere; S4, after cooling to room temperature, grinding again to obtain a cation vacancy type garnet near-infrared phosphor.

4. The method for preparing a cationic vacancy type garnet near-infrared phosphor according to claim 3, wherein: The Ca raw material is CaCO3 powder.

5. The method for preparing a cationic vacancy type garnet near-infrared phosphor according to claim 3, wherein: The Eu raw material is Eu2O3 powder.

6. The method for preparing a cationic vacancy type garnet near-infrared phosphor according to claim 3, wherein: The Sc raw material is Sc2O3 powder.

7. The method for preparing a cationic vacancy type garnet near-infrared phosphor according to claim 3, wherein: The Si raw material is nano-SiO2 powder with a particle size of 45-55nm.

8. The method for preparing a cationic vacancy type garnet near-infrared phosphor according to claim 3, wherein: In step S1, anhydrous ethanol is added in 1 to 4 times, and the amount added each time accounts for 2% to 6% of the total mass of the powder.

9. The method for preparing a cationic vacancy type garnet near-infrared phosphor according to claim 3, wherein: In step S3, the heating rate is 3-5°C / min, the holding time is 2-6 hours, and the cooling rate is 3-5°C / min.

10. The method for preparing a cationic vacancy garnet near-infrared phosphor according to claim 3, characterized in that: In step S3, the reducing atmosphere is a mixture of N2 and H2, and the volume percentage of H2 is 10-20%.

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