Nitric oxide orange red fluorescent powder with high luminous efficiency and large particle size and preparation method thereof

Abstract

The invention discloses nitric oxide orange red fluorescent powder with high luminous efficiency and large particle size and a preparation method thereof, and belongs to the field of fluorescent powder. The general molecular formula of the fluorescent powder is Ca < 1-x-y > Li < x > Al < 1-x-y > Si < 1 + x + y > N < 3-y > O < y >: zCe < 3 + >, Ce enters a crystal lattice of Ca and serves as a light-emitting element and an activating agent, 0 lt; x is less than or equal to 0.3, 0lt; y is less than or equal to 0.3, 0lt; and z < = 0.05. The fluorescent powder is sintered twice, and the second sintering is that the first sintering material and the raw materials are mixed and then sintered. The relative intensity of the fluorescent powder corresponding to an absorption peak at 25 DEG C and g = 4.215 + / -0.005 in an electron spin resonance method is 4.5 * 10 < 6 > or less. The fluorescent powder has the advantages of uniform particles, large average particle size, high quantum efficiency and high thermal stability. The method is suitable for large-scale production, and regulation and control of the particle size and uniformity can be achieved by adjusting the raw material ratio.

Description

Technical Field

[0001] The present invention relates to the field of phosphors, and particularly to a nitrogen oxide orange-red phosphor with high luminous efficiency and large particle size and a preparation method thereof. Background Art

[0002] CALSON phosphor is a nitrogen oxide phosphor including six chemical elements of Ca, Al, Li, Si, N, and O. It is a ternary solid solution formed by the solid solution of CaAlSiN3 with LiSi2N3 and Si2N2O, and the formed solid solution belongs to the wurtzite crystal structure.

[0003] CALSON:Ce 3+ The orange-red nitrogen oxide phosphor is a rare-earth doped CALSON phosphor, and its emission peak can be adjusted to be between 580 and 600 nm, which has a redder emission than YAG:Ce 3+ most widely used in the market. Therefore, the orange-red light generated has a lower color temperature and a higher color rendering index. It has a wide full width at half maximum (135 - 160 nm) and is mainly used in lighting devices. The wide full width at half maximum is more conducive to the true reflection of the color of objects.

[0004] However, at present, CALSON:Ce 3+ has the disadvantages of small crystal particles and low luminous efficiency. For example, in the literature "Ternary solid solution phosphors Ca 1-x-y Li x Al 1-x-y Si 1+x+y N 3-y O y :Ce 3+ with enhanced thermal stability for high-power laser lighting", the prepared CALSON:Ce 3+ orange-red nitrogen oxide phosphor has an external quantum efficiency of only 41.5%, and the average particle size is about 10 μm. And there are different disadvantages in other Ce 3+ doped phosphors. For example, in the literature "Extra-Broad Band Orange-Emitting Ce 3+-Doped Y3Si5N9O Phosphor for Solid-State Lighting: Electronic》. Zhu, Q.-Q., Wang, L., Hirosaki, N., Hao, L.Y., Xu, X., Xie, R.-J., Chem. Mater. 28, 4829-4839 (2016) discloses Y3Si5N9O:Ce 3+ Under excitation at 450 nm, it exhibits red light emission with a peak at 620 nm and a full width at half maximum (FWHM) of 178 nm. However, its internal quantum yield is only 17.2%, and there is still a long way to go before practical applications; the literature "Red-Emitting Cerium-Based Phosphor Materials for Solid-State Lighting Applications". Toquin, R. Le, Cheetham, A. K., Chem. Phys. Lett., 423, 352-356 (2006) discloses cubic phase CaSiN2:Ce 3+ It exhibits deep red emission light in the region of 550 - 700 nm, but its excitation spectrum is in the yellow-green light range and cannot be effectively excited by blue light.

[0005] The particle size of the phosphor will affect the luminous efficiency and subsequent applications. Therefore, there is an urgent need to prepare CALSON orange-red oxynitride phosphor with large particle size for lighting. Summary of the Invention

[0006] The object of the present invention is to solve the above problems in the prior art and provide a CALSON:Ce orange-red oxynitride phosphor with high luminous efficiency and large particle size 3+ to solve the problems of low luminous efficiency and small particle size commonly existing in the existing phosphors around 580 nm. The present invention also provides a preparation method of a CALSON:Ce orange-red oxynitride phosphor with high luminous efficiency and large particle size 3+ to prepare a CALSON:Ce orange-red oxynitride phosphor with large particle size and uniform particle size distribution and high luminous efficiency. 3+ Orange-red oxynitride phosphor.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A preparation method of an orange-red oxynitride phosphor with high luminous efficiency and large particle size, comprising the following steps:

[0009] 1) Weigh the raw materials: The CALSON:Ce3+ The general formula of orange-red nitrogen oxide phosphor is Ca 1-x-y Li x Al 1-x- y Si 1+x+y N 3-y O y :zCe 3+ , where 0 <x≤0.3,0<y≤0.3,0<z≤0.05,Ce元素进入Ca的晶体格位,作为发光元素和激活剂;按通式中各元素的化学计量比分别称取相应的原料,置于研钵中,在充满N2气氛的手套箱中进行研磨,之后装入坩埚中;

[0010] 2) Sintering: First, the raw materials are sintered for the first time in a N2 atmosphere to obtain a first sintered material; the first sintered material is ground and sieved, and then the raw materials are added thereto, and the raw materials are ground and mixed and then loaded into a crucible, and then the second sintering is carried out in a N2 atmosphere to obtain a second sintered material;

[0011] 3) Annealing: anneal the second sintered material obtained in step 2), then cool it, grind it and sieve it;

[0012] 4) Post-treatment: The sintered material after screening in step 3) is acid-washed, then washed with water and ethanol, and finally dried to obtain the phosphor.

[0013] The raw materials include Si single substance or Si compound or a mixture of the two, Al single substance or Al compound or a mixture of the two, Li compound and Ce compound; the Si compound is at least one of Si3N4 and SiO2, and the Si3N4 is α-Si3N4 and / or β-Si3N4; the Al compound is at least one of AlN and Al2O3; the Li compound is at least one of Li3N and LiF; the Ce compound is at least one of CeN and Ce2O3.

[0014] The first sintering has a sintering time of 1 to 15 hours, a sintering temperature of 1500 to 2000° C., and a sintering pressure of 0.1 to 1 MPa.

[0015] The second sintering has a sintering time of 2 to 20 hours, a sintering temperature of 1500 to 2000° C., and a sintering pressure of 0.1 to 1 MPa.

[0016] The annealing temperature is 1000-1200° C. and the time is 4-10 hours.

[0017] In the second sintering of step 2), the mass ratio of the first sintering material to the raw material is 1:(0.1~10).

[0018] The crucible is a BN crucible with a purity > 99%.

[0019] The acid used for pickling is hydrochloric acid, with a mass concentration of 13% - 37%. The pickling duration is 1 - 24 h, and the pickling temperature is 25 - 100 °C. After pickling, ultrasonic cleaning is performed three times. The first time uses pure water, and the last two times use alcohol. After cleaning, it is heated and dried in an electrothermal blast drying oven.

[0020] A nitrogen oxide orange - red phosphor with high luminous efficiency and large particle size is prepared by the above - mentioned preparation method.

[0021] Electron Spin Resonance (also known as ESR) refers to the phenomenon that the energy levels of unpaired electrons split due to the Zeeman effect in a magnetic field, and the unpaired electrons absorb electromagnetic waves with the same energy as the energy level splitting. Relevant information such as the absorption intensity and absorption wavelength of the absorption spectrum can be obtained by the ESR method. By measuring the relative intensity corresponding to the absorption peak at 25 °C and g = 4.215 ± 0.005 in the electron spin resonance method, CALSON:Ce 3+ The luminescence characteristics of the orange - red nitrogen oxide phosphor

[0022] The CALSON:Ce described in the present invention 3+ For the orange - red nitrogen oxide phosphor, the relative intensity corresponding to the absorption peak at 25 °C and g = 4.215 ± 0.05 in the electron spin resonance method is 4.5×10 6 The following. This shows that the present invention can obtain phosphors with high quantum efficiency.

[0023] Compared with the prior art, the beneficial effects achieved by the technical solution of the present invention are as follows:

[0024] The CALSON:Ce prepared by the present invention 3+ The nitrogen oxide orange - red phosphor has uniform particles, large size, high luminous efficiency, and is suitable for preparing LED lighting devices with a high color rendering index.

[0025] The process method of the present invention is simple to operate, has a wide process window, is suitable for large - scale industrial production, and can realize the preparation of CALSON:Ce 3+ The nitrogen oxide orange - red phosphor with high luminous efficiency and large particle size. Description of the Drawings

[0026] Figure 1 It is the scanning electron microscope image of the phosphor in Example 9.

[0027] Figure 2 For the comparative example Ca 0.735 Li 0.15 Al 0.75 Si1.25 N 2.9 O 0.1 : 0.01Ce 3+ Scanning electron microscope image of the phosphor.

[0028] Figure 3 XRD patterns of the phosphors prepared in Examples 1 - 4.

[0029] Figure 4 ESR comparison charts of the phosphors prepared in Examples 1 - 4.

[0030] Figure 5 Excitation spectrum of the phosphor prepared in Example 1.

[0031] Figure 6 Emission spectrum of the phosphor prepared in Example 1. Detailed implementation manners

[0032] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0033] The high-temperature solid-state method provided by the present invention for synthesizing CALSON:Ce 3+ phosphor, whose chemical general formula is Ca 1-x- y Li x Al 1-x-y Si 1+x+y N 3-y O y : zCe 3+ .

[0034] In the formula, Si is Si element, Si compound or a mixture of both, that is, at least one of Si powder, Si3N4 and SiO2. Al is Al element, Al compound or a mixture of both, that is, at least one of Al powder, AlN and Al2O3. Li is Li compound, that is, at least one of Li3N and LiF. Ce is Ce compound, that is, at least one of CeN and Ce2O3.

[0035] In the formula, 0 < x ≤ 0.3, 0 < y ≤ 0.3, 0 < z ≤ 0.05.

[0036] Comparative Example 1

[0037] According to the literature "Ternary solid solution phosphors Ca 1-x-y Li x Al 1-x-y Si 1+x+y N 3-y O y : Ce 3+ Repeated experiments were carried out according to the method disclosed in "Enhanced Thermal Stability for High - power Laser Lighting", as follows:

[0038] Ca 0.735 Li 0.15 Al 0.75 Si 1.25 N 2.9 O 0.1 :0.01Ce 3+ The raw materials used were Ca3N2, Li3N, AlN, SiO2, α - Si3N4, and CeN. The raw materials were weighed according to the ratio of the chemical formula, and the raw materials were ground in a glove box filled with a nitrogen atmosphere. The ground sample was transferred to a BN crucible and sintered at 1800 °C for 2 h under a N2 atmosphere of 0.9 MPa. Thus, Ca 0.735 Li 0.1 5Al 0.75 Si 1.25 N 2.9 O 0.1 :0.01Ce 3+ phosphor was prepared.

[0039] The external quantum efficiency of the prepared phosphor was tested, and electron microscopy scanning was carried out. The external quantum efficiency of the prepared phosphor was 35.3%. As Figure 2 shown, the particle size of this phosphor is small, and D50 is only 10 μm.

[0040] Example 1

[0041] Preparation of CALSON:Ce 3+ Preparation of phosphor:

[0042] (1) Preparation was carried out using Ca3N2, Li3N, AlN, SiO2, α - Si3N4, and CeN as raw materials. They were weighed according to the molar ratio Ca3N2:LiN3:AlN:SiO2:α - Si3N4:CeN = 0.24:0.05:0.75:0.05:0.4:0.02. The weighing must be carried out in a glove box filled with a nitrogen atmosphere (water content < 1 ppm, oxygen content < 1 ppm).

[0043] (2) The weighed raw materials were put into a mortar and ground for 0.5 h to make the raw materials evenly mixed, then passed through a 50 - mesh sieve and loaded into a BN crucible.

[0044] (3) First sintering: The BN crucible was placed in a gas - pressure furnace. First, the mechanical pump was used to pump air to below 10 Pa, and then the molecular pump was used to pump air to 10 -3The amount of Pa is at the order of magnitude, and then it is heated to 500 °C. Then, high-purity nitrogen is filled into the pressure furnace at a rate of 20 L / min to make the pressure in the furnace reach 0.9 MPa. After that, it is heated at a rate of 500 °C / h. After heating to 1900 °C, it is kept warm for 4 h. The pressure in the furnace is kept at 0.9 MPa during the sintering process.

[0045] (IV) Second sintering: After taking out the materials from the first sintering, they are ground, and then placed in a mortar with the previously weighed raw materials in a ratio of 5:1 and mixed in a glove box. They are loaded into a BN crucible, and the BN crucible is placed in a pressure furnace. First, it is evacuated by a mechanical pump to below 10 Pa, and then replaced by a molecular pump to evacuate to 10 -3 Pa order of magnitude. Then it starts to be heated to 500 °C, and then high-purity nitrogen is filled into the pressure furnace at a rate of 20 L / min to make the pressure in the furnace reach 0.9 MPa. After that, it is heated at a rate of 500 °C / h. After heating to 1900 °C, it is kept warm for 6 h. The pressure in the furnace is kept at 0.9 MPa during the sintering process.

[0046] (V) Annealing: After keeping warm for 6 h, the temperature is lowered to 1000 °C and kept warm for 2 h, then naturally cooled to room temperature. After taking out, it is ground and sieved to obtain the sieved product.

[0047] (VI) Post-treatment: The sieved product is stirred and pickled with 15 wt% hydrochloric acid at a pickling temperature of 50 °C for 2 h. After pickling, it is ultrasonically cleaned with water and ethanol respectively, and finally dried in an electrothermal blast drying oven at 60 °C for 8 h to obtain the finished orange-red phosphor CALSON:Ce 3+ 。

[0048] 50 mg of the phosphor prepared in Example 1 is placed in a test tube and measured by the ESR method at room temperature. The measuring device is an ESR measuring device (EMX-10 / 12 type) manufactured by BRUKER of Germany. The measuring conditions are as follows:

[0049] Measuring band: X band

[0050] Modulation frequency: 100 kHz

[0051] Output power: 20 mw

[0052] Modulation amplitude: 0.2 Mt

[0053] The relative intensity of the phosphor in Example 1 corresponding to the absorption peak at 25 °C and g = 4.215 ± 0.005 is 3.18×10 6 。At the same time, it has a broad excitation band ( Figure 5 ), can be excited by 450 nm blue light, can meet the lighting requirements, and the emission peak is located at 591 nm (Figure 6 ), has a redder emission than the most widely used YAG:Ce in the market. Due to its large grains, it can effectively avoid the reflection of incident light, thus enhancing the luminescent performance. 3+ With large grains, it can effectively avoid the reflection of incident light, thereby enhancing the luminescent performance.

[0054] Examples 2 - 4

[0055] Referring to Example 1, change the first sintering temperature in Step 3, while keeping other process conditions unchanged. The diffraction peaks of XRD remain almost unchanged, and the impurity peak of AlN gradually decreases with the increase of temperature. When the temperature reaches 2000, the diffraction peaks of the sample change ( Figure 3 as shown). The external quantum efficiency of the obtained phosphor, the particle size, and the relative intensity of the absorption peak of ESR are summarized in Table 1. When the sintering temperature reaches 1900 °C, the relative intensity of the ESR absorption peak is the lowest at 3.18×10 6 (as Figure 4 shown), the particle size reaches 18.4 μm, and the external quantum efficiency can reach 52.6%, indicating that this temperature is the optimal sintering temperature.

[0056] Table 1

[0057]

[0058] Examples 5 - 7

[0059] Referring to Example 1, change the ratio of the first sintered material to the raw material in Step 4, while keeping other process conditions unchanged. The external quantum efficiency of the obtained phosphor, the particle size, and the relative intensity of the absorption peak of ESR are summarized in Table 2. Different ratios have different ESR absorption peaks. When the ratio of the first sintered material to the raw material is 1:4, the ESR absorption peak is the lowest at 2.69×10 6 , the particle size reaches the largest at 23.5 μm, and the external quantum efficiency reaches the highest at 58.6%.

[0060] Table 2

[0061]

[0062] Examples 8 - 10

[0063] Referring to Example 6, change the hydrochloric acid concentration for pickling in Step 6, while keeping other process conditions unchanged. The external quantum efficiency of the obtained phosphor, the particle size, and the relative intensity of the absorption peak of ESR are summarized in Table 3. Adjusting different hydrochloric acid mass concentrations can change the relative intensity of the ESR absorption peak. When the hydrochloric acid concentration in Example 9 is 23.5%, the relative intensity of the obtained ESR absorption peak is the lowest at 2.54×10 6 , and the particle size is 25.6 μm ( Figure 1(which is the corresponding scanning electron microscope image), and the external quantum efficiency reaches 64.1%.

[0064] Table 3

[0065]

[0066] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all fall within the protection scope of the present invention.

Claims

1. A preparation method of a nitrogen oxide orange-red phosphor with high luminous efficiency and large particle size, characterized in that, It includes the following steps: 1) Weigh the raw materials: The general formula of the phosphor is Ca 1-x-y Li x Al 1-x-y Si 1+x+y N 3-y O y :zCe 3+ , where 0 < x ≤ 0.3, 0 < y ≤ 0.3, 0 < z ≤ 0.05; Weigh the corresponding raw materials according to the stoichiometric ratios of the elements in the general formula, place them in a mortar, grind them in a glove box filled with N2 atmosphere, and then load them into a crucible; 2) Sintering: First, sinter the raw materials in an N2 atmosphere for the first time to obtain the first sintered material; Grind the first sintered material, after sieving, add raw materials thereto, grind and mix them and then load them into a crucible, and then sinter for the second time in an N2 atmosphere to obtain the second sintered material; 3) Annealing: Anneal the second sintered material obtained in step 2), then cool it, grind it and then sieve it; 4) Post-treatment: Pickle the sintered material sieved in step 3) with acid, then wash it with water and ethanol, and finally dry it to obtain the phosphor.

2. The preparation method of a nitrogen oxide orange-red phosphor with high luminous efficiency and large particle size as described in claim 1, characterized in that: The raw materials include Si element or Si compound or a mixture of both, Al element or Al compound or a mixture of both, Li compound and Ce compound; the Si compound is at least one of Si3N4 and SiO2, and the Si3N4 is α-Si3N4 and / or β-Si3N4; the Al compound is at least one of AlN and Al2O3; the Li compound is at least one of Li3N and LiF; the Ce compound is at least one of CeN and Ce2O3.

3. The preparation method of a nitrogen oxide orange-red phosphor with high luminous efficiency and large particle size according to claim 1, characterized in that: For the first sintering, the sintering time is 1 to 15 h, the sintering temperature is 1500 to 2000 °C, and the sintering pressure is 0.1 to 1 MPa.

4. The preparation method of a nitrogen oxide orange-red phosphor with high luminous efficiency and large particle size as described in claim 1, characterized in that: For the second sintering, the sintering time is 2 to 20 h, the sintering temperature is 1500 to 2000 °C, and the sintering pressure is 0.1 to 1 MPa.

5. The preparation method of a nitrogen oxide orange-red phosphor with high luminous efficiency and large particle size as described in claim 1, characterized in that: For the annealing, the temperature is 1000 to 1200 °C and the time is 4 to 10 h.

6. The preparation method of a nitrogen oxide orange-red phosphor with high luminous efficiency and large particle size according to claim 1, characterized in that: In the second sintering of step 2), the mass ratio of the first sintered material to the raw materials is 1:(0.1 to 10).

7. The preparation method of a nitrogen oxide orange-red phosphor with high luminous efficiency and large particle size as described in claim 1, characterized in that: The crucible is a BN crucible with a purity > 99%.

8. The preparation method of a nitrogen oxide orange-red phosphor with high luminous efficiency and large particle size as described in claim 1, characterized in that: The acid used for pickling is hydrochloric acid, the mass concentration of hydrochloric acid is 13% to 37%, the pickling duration is 1 to 24 h, and the pickling temperature is 25 to 100 °C.

9. A nitrogen oxide orange-red phosphor with high luminous efficiency and large particle size, characterized in that: Prepared by using the preparation method according to any one of claims 1 to 8.

10. A nitrogen oxide orange-red phosphor with high luminous efficiency and large particle size as described in claim 9, characterized in that: The relative intensity of the phosphor corresponding to the absorption peak at 25 °C and g = 4.215 ± 0.05 in the electron spin resonance method is 4.5×10 6 or less.

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