Preparation method of gallium aluminate fluorescent powder

Abstract

The invention belongs to the technical field of LED luminescent materials, and relates to a preparation method of gallium aluminate fluorescent powder, which comprises the following steps: (1) uniformly mixing raw materials, and adding a fluxing agent; (2) putting the material into an alumina crucible, and carrying out high-temperature calcination in a low-hydrogen environment; (3) crushing and sieving solid fluorescent powder; (4) pickling treatment; and (5) drying, cooling and sieving. The production cost of the fluorescent powder is effectively reduced, the optical performance of the fluorescent powder is improved, the physical and chemical properties are stable, the fluorescent powder does not react with water, oxygen and carbon dioxide in a high-temperature and high-humidity environment, and the fluorescent powder is heat-resistant, non-toxic and pollution-free; the preparation method of the gallium aluminate fluorescent powder is simple, easy to operate, free of pollution and easy to industrialize.

Description

Technical Field

[0001] The invention belongs to the technical field of LED luminescent materials, and in particular relates to a method for preparing gallium aluminate phosphor. Background Art

[0002] Since the light emitting diode (LED) was first successfully developed by Nichia Corporation in Japan in the 1990s, LED has been hailed as the green light source of the new century due to its excellent performance, such as high luminous efficiency, long service life, high color rendering index, energy saving, environmental friendliness and high stability. 1-x Re x )3Al 5-z M z O 12 :Ce 3+ (Re=Gd, Lu, La, Yb, Tb, M=Ga) The performance of phosphor is one of the key factors affecting the quality of the device. Therefore, a large part of the research on LEDs is focused on the preparation and modification of phosphor powders. The high-temperature solid-phase method is simple and mature, and it is easy to achieve mass production of powders. This method is generally used to synthesize phosphors.

[0003] The current LED phosphor market is highly competitive. While ensuring the steady improvement of product quality, reducing the preparation cost is a reality that must be faced in the market competition. Only low-cost companies have a competitive advantage. Under the premise of not changing the luminous properties of phosphors, people are constantly trying to find more suitable and effective ways to reduce production costs. For example, reducing the loss of post-processing powder, reducing labor, adding robots, and staggering electricity consumption. Among them, using the least raw materials to prepare phosphors with the same optical properties is also an important research object. Taking gallium aluminate yellow-green phosphor as an example, the price of metal gallium is relatively high. Under the same gallium oxide dosage, the shorter the wavelength of the synthesized phosphor, the more competitive it is.

[0004] Therefore, how to reduce the production cost of phosphors while preparing them by the high-temperature solid-phase method is a technical difficulty that companies must overcome at this stage. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the present invention provides a method for preparing gallium aluminate phosphor, and the specific technical scheme is as follows:

[0006] A method for preparing a gallium aluminate phosphor, wherein the gallium aluminate phosphor has a chemical formula of Y 3-x Al 5- z Ga z O 12 :Ce x 3+(0 < x ≤ 3, 0 < z ≤ 5), including the following steps:

[0007] (1) Uniformly mix the raw materials Al2O3, Ga2O3, Y2O3, and CeO2, and then add a flux and mix evenly; the flux is one or more of barium fluoride, sodium fluoride, aluminum fluoride, calcium fluoride, lithium fluoride, yttrium fluoride, aluminum chloride, calcium chloride, strontium carbonate, and sodium carbonate;

[0008] (2) Put the uniformly mixed materials in step (1) into an alumina crucible, and calcine at a high temperature of 1400 - 1600 °C for 3 - 5 hours in an environment where the hydrogen is less than 10%, and sinter and synthesize a solid phosphor;

[0009] (3) Crush the solid phosphor synthesized by sintering in step (2), and pass through a 400 - mesh sieve to remove phosphor particles with larger particle sizes or severe agglomeration to prevent color temperature deviation during use;

[0010] (4) Slowly add the phosphor sieved in step (3) to a hydrochloric acid solution at a temperature of 50 - 70 °C for pickling treatment;

[0011] (5) Dry, cool, and pass through a 200 - mesh sieve the phosphor after pickling treatment in step (4) to obtain the gallium aluminate phosphor.

[0012] The present invention adds a specific flux to the raw materials, and prepares an optical material with high luminous intensity and good thermal stability through high - temperature sintering. At the same time, the cost is effectively reduced, and the production of gallium aluminate phosphor is simple, easy to operate, pollution - free, and easy to industrialize.

[0013] Further, the flux includes aluminum fluoride or / and aluminum chloride.

[0014] Cation Al 3+ After the high - temperature reaction to generate the phosphor, it will be uniformly wrapped on the surface of the synthesized phosphor to form a thin and dense film layer, reducing the reaction between gallium oxide and hydrogen at high temperature, and then increasing the reaction amount of Ga2O3 during the synthesis of the phosphor, resulting in a shorter wavelength of the phosphor. At the same time, Al 3+ Also generates a dense protective layer on the surface of the phosphor, enhancing the high - temperature resistance performance of the phosphor and enhancing the thermal stability of the phosphor.

[0015] Further, the dosage of the flux is 4 6 wt%.

[0016] Further, the flux is barium fluoride and aluminum fluoride, and the mass ratio of barium fluoride to aluminum fluoride is 1:(0.01 - 0.03).

[0017] Furthermore, the pH of the hydrochloric acid solution is 3-5, and the pickling time is 10 60min.

[0018] The purpose of the pickling treatment is to remove the unreacted raw materials, impurities, and synthetic intermediates in the phosphor to improve the luminescence performance of the phosphor. The hydrochloric acid solution needs to be added slowly and evenly. Its purpose is to remove the impurities attached to the surface of the phosphor while reducing the increase in phosphor defects caused by the burning of the hydrochloric acid solution on the surface of the phosphor, so as to improve the luminescence intensity of the powder and increase the thermal stability of the powder.

[0019] Furthermore, in step (5), the drying temperature of the phosphor is 150-250° C., and the drying time is 400-500 min.

[0020] Furthermore, the purity of the flux is fluorescent grade.

[0021] The beneficial effects of the present invention are:

[0022] The utilization rate of gallium oxide in the production process of traditional gallium aluminate phosphors is low, which increases the production cost. The phosphor prepared by the improved method for preparing gallium aluminate phosphors of the present invention not only effectively reduces the production cost, but also improves its optical properties, has stable physical and chemical properties, does not react with water, oxygen, and carbon dioxide in a high temperature and high humidity environment, is heat-resistant, non-toxic, and harmless; and the preparation method of the gallium aluminate phosphors of the present invention is simple, easy to operate, pollution-free, and easy to industrialize. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The SEM images of the phosphor prepared in Example 1 of the present invention before and after acid washing;

[0024] Figure 2 The emission spectra of the phosphors synthesized in various embodiments of the present invention are shown in FIG. DETAILED DESCRIPTION

[0025] The principles and features of the present invention are described below in conjunction with embodiments. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0026] Embodiment 1:

[0027] A gallium aluminate phosphor (Y 2.935 Al 3.5 Ga 1.5 O 12 :Ce 0.065 3+ ) is prepared, comprising the steps of:

[0028] (1) Calculate the mass of each reactant required to produce 500 g of phosphor, then use an electronic balance to accurately weigh the initial raw materials Y2O3 = 250.64 g, Al2O3 = 134.95 g, CeO2 = 8.462 g, Ga2O3 = 106.33 g, and 25 g of flux barium fluoride; first mix the raw materials Y2O3, Al2O3, CeO2, and Ga2O3 evenly, then add the flux barium fluoride to the raw materials and mix them thoroughly;

[0029] (2) the uniformly mixed materials are loaded into an alumina crucible, placed in a reducing furnace, and calcined at 1500° C. for 4 hours in an environment where the volume fraction of hydrogen is less than 10%;

[0030] (3) After the sintering process is completed, the solid phosphor obtained by sintering is crushed and passed through a 400-mesh nylon sieve to remove phosphor particles with large particles or serious agglomeration to prevent color temperature deviation during use;

[0031] (4) Slowly adding the sieved phosphor powder in step (3) into a dilute hydrochloric acid solution with a pH of 4 and a temperature of 60° C., and performing an acid wash treatment for 30 minutes to remove impurities and small particles in the phosphor powder, and finally obtaining a phosphor powder with a certain strength range;

[0032] (5) Drying the phosphor after the acid washing treatment at 200° C. for 450 min, cooling to room temperature, and passing through a 200-mesh sieve to obtain the gallium aluminate phosphor.

[0033] The phosphors in the embodiment were optically tested before and after pickling. The test results are as follows: Figure 1 As shown, from Figure 1 It can be clearly seen that the particle size of the phosphor after post-processing is relatively concentrated, with D50 at around 22um, and there is almost no agglomeration between the powders. In addition, the phosphor particles are angular, which means that the phosphor has almost no crystal defects caused by crushing and post-processing, and the impurities attached to the surface of the phosphor particles have also been effectively removed.

[0034] Embodiment 2:

[0035] A gallium aluminate phosphor (Y 2935 Al 34 Ga 16 O 12 :Ce 0065 3+ ) is prepared, comprising the steps of:

[0036] (1) Calculate the mass of each reactant required to produce 500g of phosphor, then use an electronic balance to accurately weigh the initial raw materials Y2O3 = 249.03g, Al2O3 = 130.26g, CeO2 = 8.407g, Ga2O3 = 112.69g, and 25g of flux barium fluoride; first mix the raw materials Y2O3, Al2O3, CeO2, and Ga2O3 evenly, then add the flux barium fluoride to the raw materials and mix them thoroughly;

[0037] (2) the uniformly mixed materials are loaded into an alumina crucible, placed in a reducing furnace, and calcined at 1500° C. for 4 hours in an environment where the volume fraction of hydrogen is less than 10%;

[0038] (3) After the sintering process is completed, the solid phosphor obtained by sintering is crushed and passed through a 400-mesh nylon sieve to remove phosphor particles with large particles or serious agglomeration to prevent color temperature deviation during use;

[0039] (4) Slowly adding the sieved phosphor powder in step (3) into a dilute hydrochloric acid solution with a pH of 4 and a temperature of 60° C., and performing an acid wash treatment for 30 minutes to remove impurities and small particles in the phosphor powder, and finally obtaining a phosphor powder with a certain strength range;

[0040] (5) Drying the phosphor after the acid washing treatment at 200° C. for 450 min, cooling to room temperature, and passing through a 200-mesh sieve to obtain the gallium aluminate phosphor.

[0041] Embodiment 3:

[0042] A gallium aluminate phosphor (Y 2.935 Al 3.8 Ga 1.2 O 12 :Ce 0.065 3+ ) is prepared, comprising the steps of:

[0043] (1) Calculate the mass of each reactant required to generate 500g of phosphor, then use an electronic balance to accurately weigh the initial raw materials Y2O3 = 250.64g, Al2O3 = 134.95g, CeO2 = 8.462g, Ga2O3 = 106.33g, and the flux barium fluoride 25g and aluminum fluoride 0.6g; first mix the raw materials Y2O3, Al2O3, CeO2, and Ga2O3 evenly, then fully mix the flux barium fluoride and aluminum fluoride, and then add them to the raw materials and mix them evenly;

[0044] (2) the uniformly mixed materials are loaded into an alumina crucible, placed in a reducing furnace, and calcined at 1500° C. for 4 hours in an environment where the volume fraction of hydrogen is less than 10%;

[0045] (3) After the sintering process is completed, the solid phosphor obtained by sintering is crushed and passed through a 400-mesh nylon sieve to remove phosphor particles with large particles or serious agglomeration to prevent color temperature deviation during use;

[0046] (4) Slowly adding the sieved phosphor powder in step (3) into a dilute hydrochloric acid solution with a pH of 4 and a temperature of 60° C., and performing an acid wash treatment for 30 minutes to remove impurities and small particles in the phosphor powder, and finally obtaining a phosphor powder with a certain strength range;

[0047] (5) Drying the phosphor after the acid washing treatment at 200° C. for 450 min, cooling to room temperature, and passing through a 200-mesh sieve to obtain the gallium aluminate phosphor.

[0048] Table 1 Comparison of the amount of raw material gallium oxide used in Example 2 and Example 3

[0049] name Amount of gallium oxide (g) Less dosage% Example 2 112.69 Example 3 106.33 -5.98％

[0050] Figure 2 The emission spectra of the phosphors synthesized in the embodiments of the present invention are shown in the figure. It can be clearly seen from the figure that, compared with Embodiment 1, Embodiment 3 has a blue shift in the spectrum of the synthesized phosphor due to the addition of a composite flux of barium fluoride and aluminum fluoride, and the spectrum of the phosphors of Embodiment 3 and Embodiment 2 completely overlap, which is better than the phosphor synthesized in Embodiment 1. From the comparison of the amount of raw material gallium oxide used in Embodiment 2 and Embodiment 3 in Table 1, it can be seen that the amount of gallium oxide used in Embodiment 3 is 6.36 grams less than that in Embodiment 2, saving 5.98% of gallium oxide. Embodiment 3 reduces the amount of high-priced gallium oxide, blue-shifts the wavelength of the phosphor, increases the utilization rate of gallium oxide, and effectively reduces the production cost. This is because during the high-temperature solid-phase synthesis process of the phosphor in Embodiment 3, the Al in the added aluminum fluoride 3+ A thin and dense film layer is formed on the surface of the raw material, which reduces the reaction of gallium oxide with hydrogen at high temperature, thereby increasing the number of reactions of Ga2O3 in the process of synthesizing phosphors, resulting in a shorter wavelength of the phosphors. At the same time, Al in aluminum fluoride 3+ A dense protective layer is also generated on the surface of the phosphor, which enhances the high temperature resistance of the phosphor.

[0051] Table 2 Relative brightness change values ​​of phosphors in Example 2 and Example 3 at different temperatures

[0052]

[0053] Table 2 shows the relative brightness change values ​​of the phosphors of Example 2 and Example 3 at different temperatures. It can be seen that when the temperature of the powder tray is lower than 100°C, the luminous intensity remains almost unchanged; when the ambient temperature increases from 100°C to 172°C, the luminous intensity increases first and then decreases with the increase of the ambient temperature. However, during this change, the optical properties of Example 3 are higher than the initial optical properties, indicating that the Al in the added aluminum fluoride is 3+ The protective film formed not only enhances the thermal stability of the phosphor but also improves the luminescence performance of the phosphor. Most importantly, it reduces the synthesis cost of the phosphor.

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a gallium-aluminate phosphor, characterized in that: The chemical formula of the gallium aluminate phosphor is Y 3- x Al 5-z Ga z O 12 :Ce x 3+ (0 < x ≤ 3, 0 < z ≤ 5), comprising the following steps: (1) uniformly mixing raw materials Al2O3, Ga2O3, Y2O3, and CeO2, and then adding a flux and mixing uniformly; the flux is one or more of barium fluoride, sodium fluoride, aluminum fluoride, calcium fluoride, lithium fluoride, yttrium fluoride, aluminum chloride, calcium chloride, strontium carbonate, and sodium carbonate; (2) placing the uniformly mixed materials in step (1) into a crucible, and calcining them at 1400-1600° C. for 3-5 hours in an environment where hydrogen is less than 10 v %, to form a solid phosphor; (3) crushing the solid phosphor powder sintered in step (2), and sieving to remove phosphor powder particles with large particles or serious agglomeration; (4) Slowly adding the sieved phosphor in step (3) into a hydrochloric acid solution at a temperature of 50-70° C. for pickling; (5) Drying, cooling, and sieving the phosphor after the acid washing in step (4) to obtain the gallium aluminate phosphor.

2. The method for preparing the gallium aluminate phosphor according to claim 1, characterized in that: The flux includes aluminum fluoride and / or aluminum chloride.

3. The method for preparing the gallium aluminate phosphor according to claim 1, characterized in that: The amount of the flux is 4-6% of the total weight of the raw materials.

4. The method for preparing the gallium aluminate phosphor according to claim 1, characterized in that: The flux is barium fluoride and aluminum fluoride, and the mass ratio of the barium fluoride to the aluminum fluoride is 1:(0.01-0.03).

5. The method for preparing the gallium aluminate phosphor according to claim 1, characterized in that: The pH of the hydrochloric acid solution is 3-5, and the pickling treatment time is 10-60 minutes.

6. The method for preparing the gallium aluminate phosphor according to claim 1, characterized in that: In the step (5), the phosphor is dried at a temperature of 150-250° C. and for a drying time of 400-500 min.

7. The method for preparing the gallium aluminate phosphor according to claim 1, characterized in that: The purity of the flux is fluorescent grade.

Images