WO2021012393A1

WO2021012393A1 - Red phosphor powder and preparation method and application thereof

Info

Publication number: WO2021012393A1
Application number: PCT/CN2019/109527
Authority: WO
Inventors: 王忆; 罡一帆; 龙祥杰
Original assignee: 五邑大学
Priority date: 2019-07-19
Filing date: 2019-09-30
Publication date: 2021-01-28
Also published as: CN110499159A

Abstract

The present invention relates to a red phosphor powder and a preparation method and application thereof, belonging to the technical field of phosphors used for light-emitting diodes (LEDs) in the field of lighting and display. The present invention uses a compound containing molybdenum ions as a matrix, doped with rare earth element europium ions, yttrium ions, and alkali metal ions to prepare a red phosphor, having the chemical formula M_nY_1-xEu_x(MoO4)2 (M is alkaline metal; n = 0.10–1.5; x = 0.1–0.5). The red phosphor prepared by the present invention can be simultaneously excited by ultraviolet light, blue light, and green light to effectively excite red light having a higher luminous intensity; the preparation process of the molybdate red phosphor provided by the invention is simple, and the process is easy to operate and suitable for use in industrial production.

Description

Red phosphor and preparation method and application thereof

Technical field

The invention relates to a red phosphor and a preparation method and application thereof, and belongs to the technical field of phosphors for light emitting diodes (LEDs) in the field of lighting and display.

Background technique

The concept of "green lighting" was first proposed in the early 1990s and attracted great attention from countries all over the world. Green lighting requires not only high-efficiency and energy-saving lighting tools, but also environmental protection, safety and comfort of lamps and lanterns under the situation of increasingly serious global pollution. Under the background, light-emitting diodes gradually entered the public's field of vision. At present, most of the white LED lamps used in the market use a blue chip to excite yellow phosphors to obtain white light, or an ultraviolet chip to excite three primary color phosphors to mix to obtain white light. It can be seen from the above methods to realize white light LED that the luminous performance of phosphors is one of the main factors restricting the development of white light LEDs, and the reasons that affect the luminous performance of phosphors include many aspects, such as the stability of the properties of synthetic phosphors. The light conversion efficiency of the phosphor and the stability of the luminescent wavelength of the phosphor have a great influence on the realization of white LEDs. Red phosphor can improve the color purity of white light and increase the color rendering index. However, from the current research situation, compared with the more mature preparation technology of yellow phosphor and green phosphor, it is becoming more and more important in white light LED. The research work on red phosphors is still at a relatively immature stage, so how to research and develop stable and efficient red phosphors is one of the main difficulties that need to be overcome in the current white LED research field.

Summary of the invention

The technical problem to be solved by the present invention is: based on the above problems, the present invention relates to a Eu ³⁺ activated red phosphor and its preparation method and application. A technical solution adopted by the present invention to solve its technical problems is:

A Eu ³⁺ activated molybdate red phosphor. The chemical formula of the red phosphor is M _n Y _1-x Eu _x (MoO ₄ ) ₂ , the value of x is 0.1-0.5, M is alkaline metal, n The value is 0.10-1.5.

Preferably, the value of x is 0.2-0.4. More preferably, the value of x is 0.3. When the europium ion concentration is 0.3 mol, the prepared red phosphor sample has the strongest luminous intensity, which can be effectively excited by green light of 537 nm and emit red light of about 619 nm.

Preferably, the alkaline metal is one or more of Li, Na and K. More preferably, the alkaline metal is Li, and when the Eu ³⁺ concentration is 0.3 mol, the spectral test result shows that the sample with the highest relative luminescence intensity is the sample doped with Li ⁺ .

Preferably, the value of n is 0.25-1. When the alkali metal ion concentration is 0.25-1 mol, the emission intensity of the prepared red phosphor sample is relatively strong.

The invention also provides a method for preparing the red phosphor, which includes the following steps:

Dissolving compounds containing lithium ions, compounds containing sodium ions, compounds containing potassium ions, compounds containing yttrium ions, and compounds containing europium ions respectively with nitric acid, and mixed with compounds containing molybdenum ions and organic acids to obtain a mixed solution;

Stir the obtained mixture solution to adjust the pH value;

The mixture solution after adjusting the pH value is dried, and then calcined to obtain a red phosphor.

Preferably, the compound containing lithium ions is one or more of lithium oxide, lithium hydroxide and lithium carbonate; the compound containing sodium ions is one or more of sodium hydroxide, sodium carbonate and sodium bicarbonate; The compound containing potassium ions is one or more of potassium oxide, potassium hydroxide and potassium carbonate.

More preferably, the compound containing lithium ions is lithium carbonate; the compound containing sodium ions is sodium carbonate; and the compound containing potassium ions is potassium carbonate.

Preferably, the compound containing yttrium ions is one or more of yttrium oxide, yttrium hydroxide and yttrium carbonate; the compound containing europium ions is one or more of europium oxide, europium hydroxide and europium carbonate; The molybdenum ion compound is one or more of ammonium molybdate, sodium molybdate and potassium molybdate; the organic acid is citric acid.

More preferably, the compound containing yttrium ions is yttrium oxide; the compound containing europium ions is europium oxide; and the compound containing molybdenum ions is ammonium molybdate.

Preferably, the obtained mixture solution is stirred at 40-90°C for 15-60 minutes to adjust the pH value of 6.5-8.5; the mixture solution after adjusting the pH value is dried at 35-150°C for 6-36 hours; It is calcined at 300-1200°C for 2-12 hours.

More preferably, the resulting mixture solution is stirred at 50-75°C for 20-40 minutes to adjust the pH value of 7-8. More preferably, the resulting mixture solution is stirred at 65°C for 30 minutes.

More preferably, the drying step is multi-stage variable temperature drying, the drying temperature in the first stage is 35-100°C, the drying time is 6-24 hours, and the drying temperature in the second stage is 90-150°C, and the drying time is 12-30 hours. More preferably, the drying temperature in the first stage is 80°C and the drying time is 24 hours, and the drying temperature in the second stage is 120°C and the drying time is 12 hours.

More preferably, the calcination step is multi-stage variable temperature calcination, the calcination temperature in the first stage is 300-750°C, the calcination time is 2-8 hours, and the calcination temperature in the second stage is 650-1200°C, and the calcination is 4-10 hours. More preferably, the firing temperature in the first stage is 500°C and the firing time is 4 hours, and the firing temperature in the second stage is 700-900°C and the firing time is 4 hours. More preferably, the second-stage firing temperature is 800°C, and the spectral test results show that when the second-stage firing temperature of the sample is 800°C, the phosphor has the best luminescence performance. The sample phosphor emits light as the annealing temperature increases. Performance drops.

Specifically, the preparation method of the Eu ³⁺ activated molybdate red phosphor adopts the sol-gel method and includes the following steps:

Dissolve lithium carbonate, sodium bicarbonate, potassium carbonate, yttrium oxide, and europium oxide with nitric acid, and mix them with ammonium molybdate and citric acid to obtain a mixture solution;

Stir the obtained mixture solution at 65°C for 30 minutes, and adjust the pH value of the mixture solution to 7-8;

The mixed solution was dried at 80°C for 24 hours and then at 120°C for 12 hours to obtain a dry powder, which was then calcined at 500°C for 4 hours and then dried at 800°C for 4 hours to obtain a red phosphor.

The present invention also provides the application of red phosphor. The red phosphor is excited by one or more of ultraviolet LED, near-ultraviolet LED, blue LED and green LED to obtain red light. The color phosphor and the green phosphor cooperate to form a broad spectrum of white light.

The blue-green fluorescent powder obtained in the present invention has been tested with a fluorescence spectrometer for luminous intensity and spectrum, and its structure has been studied by X-ray diffraction (XRD) and electron microscope scanning (SEM). The results show that the present invention has the following beneficial effects:

(1) The sample prepared by the preparation method of the present invention has uniform particle size distribution, regular particle shape, good compactness, low calcination temperature, relatively short calcination time, high purity of the formed sample, and broad application prospects;

(2) The M _n Y _1-x Eu _x (MoO ₄ ) ₂ (M is alkaline metal; n = 0.10-1.5; x = 0.1-0.5) red phosphor prepared by the present invention can be simultaneously irradiated by ultraviolet light and blue light And green light effectively excites red light (around 619nm) with high luminous intensity, blue light (around 465nm) has the highest excitation efficiency, followed by green light (around 537nm), and ultraviolet light (around 395nm) has relatively low excitation efficiency;

(3) The preparation process of the molybdate red phosphor provided by the present invention is simple, the process is easy to operate, the reaction temperature is low (300-1200 DEG C), energy consumption is saved, no exhaust gas emission is environmentally friendly, and it is suitable for industrial production.

Description of the drawings

The present invention will be further described below in conjunction with the drawings.

FIG. 1A shows the emission spectra of phosphor samples with different europium ion concentrations prepared according to Example 2.

1B is the excitation spectra of phosphor samples with different europium ion concentrations prepared according to Example 2.

2A is the emission spectra of different alkali metal ion phosphor samples prepared according to Example 3.

2B is the excitation spectra of different alkali metal ion phosphor samples prepared according to Example 3.

FIG. 3A is an XRD pattern of a red phosphor sample doped with sodium ions prepared according to Example 3. FIG.

3B is an XRD pattern of a sample of lithium ion red phosphor prepared according to Example 3.

FIG. 3C is an XRD pattern of a sample of potassium ion doped red phosphor prepared according to Example 3. FIG.

4A is the emission spectra of different concentrations of lithium ion phosphor samples prepared according to Example 4.

4B is the excitation spectra of lithium ion phosphor samples with different concentrations prepared according to Example 4.

5A is the emission spectra of sodium ion phosphor samples with different concentrations prepared according to Example 5.

FIG. 5B is the excitation spectra of sodium ion phosphor samples with different concentrations prepared according to Example 5.

6A is the emission spectra of phosphor samples prepared at different firing temperatures according to Example 6. FIG.

6B is the excitation spectra of phosphor samples prepared at different firing temperatures according to Example 6.

Fig. 7A is a scanning electron microscope image of a phosphor sample prepared according to Example 6 at a firing temperature of 700°C.

Fig. 7B is a scanning electron microscope image of a phosphor sample prepared according to Example 6 at a firing temperature of 800°C.

Fig. 7C is a scanning electron microscope image of a phosphor sample prepared according to Example 6 at a firing temperature of 900°C.

Detailed ways

The present invention will now be further described in conjunction with specific examples. The following examples are intended to illustrate the present invention but not to further limit the present invention.

Example 1

This example investigates the influence of europium ion concentration (x value) on the luminous intensity of red phosphor.

A preparation method of red phosphor includes the following steps:

(1) Weigh the required raw materials according to the chemical formula Na ₁ Y _0.7 Eu _0.3 (MoO ₄ ) ₂ stoichiometric ratio, dissolve sodium carbonate, yttrium oxide, and europium oxide with nitric acid, add ammonium molybdate tetrahydrate and citric acid to mix, Get a mixture solution;

(2) Stir the obtained mixture solution with a magnetic stirrer at 65°C for 30 minutes, and adjust the pH value of the mixture solution to 7.5;

(3) Dry the mixed solution at 80°C for 24 hours, and then increase the temperature to 120°C for another 12 hours to obtain a dry powder;

(4) Grind the dry powder into powder, calcinate at 500°C for 4 hours, raise the temperature to 800°C and calcinate for 4 hours to obtain a red phosphor.

Refer to the above-mentioned preparation method of red phosphor, when the doped alkaline metal ion is sodium ion, with Eu ³⁺ concentration as the variable, prepare three different samples Na ₁ Y _1-x Eu _x (MoO ₄ ) ₂ (x = 0.2, 0.3, 0.4). The fluorescence spectrometer voltage is set to 400V, the slit width is 2.5nm, the scanning speed is 1200nm/min, the excitation wavelength is set to 537nm when measuring the emission spectrum, and the monitoring wavelength is set to 619nm when measuring the excitation spectrum. Use F-4600 The emission spectrum and excitation spectrum of the red phosphor obtained by the fluorescence spectrometer test are shown in Figures 1A-1B.

Refer to Figure 1A, which is the emission spectrum obtained by excitation of phosphor samples with different europium ion concentrations prepared according to Example 1 under 537 nm green light. It can be seen from the figure that with the same concentration of sodium ions, when the excitation light wavelength is 537nm, when the europium ion concentration is 0.3, the sample has the strongest luminous intensity, which can be effectively excited by the green light of 537nm to about 619nm Red light.

Refer to Figure 1B, which is the excitation spectrum of phosphor samples with different europium ion concentrations prepared according to Example 1 with 619 nm red light as the monitoring wavelength. It can be seen from the figure that with the same concentration of sodium ions and the monitoring wavelength of 619nm, the sample has three excitation peaks, which are ultraviolet light around 395nm, blue light around 465nm and green light around 537nm, indicating that the sample can At the same time, it is effectively excited by ultraviolet light, blue light and green light. The highest excitation efficiency is blue light, and then to green light, the relatively low excitation efficiency is ultraviolet light.

Example 2

This example investigates the influence of different alkali metal ions on the luminous intensity of the red phosphor.

Referring to the preparation method of red phosphor in Example 1, when the Eu ³⁺ concentration is 0.3, different alkaline metal ions are doped to prepare three sets of samples M ₁ Y _0.7 Eu _0.3 (MoO ₄ ) ₂ (M=Li, Na, K). The fluorescence spectrometer voltage is set to 400V, the slit width is 2.5nm, the scanning speed is 1200nm/min, the excitation wavelength is set to 537nm when measuring the emission spectrum, and the monitoring wavelength is set to 619nm when measuring the excitation spectrum. Use F-4600 The emission spectrum and excitation spectrum of the red phosphor obtained by the fluorescence spectrometer test are shown in Figure 2A-2B. The X-ray diffraction (XRD) analysis results are shown in Figures 3A-3C.

Refer to Figure 2A, which is the emission spectrum obtained by excitation of different alkali metal ion phosphor samples prepared according to Example 2 under 537 nm green light. It can be seen from the figure that when the Eu ³⁺ concentration is 0.3, when different alkali metal ions of the same concentration are added, the spectral test results show that the sample with the highest relative luminous intensity is the sample doped with Li ⁺ . The luminous intensity of the sample It decreases with the increase of alkali metal ion radius (the order of alkali metal ion radius: Li ⁺ <Na ⁺ <K ⁺ ), and the sample can be effectively excited by green light of 537 nm and emit red light of about 619 nm.

Refer to Figure 2B, which is the excitation spectrum of different alkali metal ion phosphor samples prepared according to Example 2 with 619 nm red light as the monitoring wavelength. It can be seen from the figure that when the Eu ³⁺ concentration is 0.3, the shape of the excitation spectrum and the peak position of the samples with the same concentration of different alkali metal ions do not change, and the samples with different alkali metal ions can be absorbed by about 395nm. Ultraviolet light, blue light around 465nm and green light around 537nm are effectively excited. The difference in the excitation spectra of the three samples is the sample phosphor doped with Li ⁺ . Its strongest excitation peak is in the ultraviolet region, followed by the blue region. The relatively weakest peak is in the green region, while The strongest excitation peaks of Na ⁺ sample phosphors and K ⁺ doped sample phosphors are in the blue region, and then to the green region, the relatively weakest excitation peaks are all in the ultraviolet region.

Refer to Figures 3A-3C, which are prepared according to the technical scheme of Example 2 and doped with sodium ions, lithium ions, and potassium ions to obtain XRD patterns of red phosphor samples. It can be seen from the figure that three different Compared with the diffraction peaks of the respective standard cards, the diffraction peaks of the alkali metal ion phosphors have a small amount of impurity peaks, but they basically match the diffraction peaks of the XRD standard diffraction cards, indicating that the target phosphor products have been synthesized.

Example 3

This example investigates the effect of doping different concentrations of lithium ions on the luminescence performance of red phosphors.

Referring to the preparation method of red phosphor in Example 1, when the Eu ³⁺ concentration is 0.3, doping different concentrations of lithium ions to prepare four sets of samples Li _n Y _0.7 Eu _0.3 (MoO ₄ ) ₂ (n=0.25, 0.5, 0.75 ,1). The fluorescence spectrometer voltage is set to 400V, the slit width is 2.5nm, the scanning speed is 1200nm/min, the excitation wavelength is set to 537nm when measuring the emission spectrum, and the monitoring wavelength is set to 619nm when measuring the excitation spectrum. Use F-4600 The emission spectrum and excitation spectrum of the red phosphor obtained by the fluorescence spectrometer test are shown in Figure 4A-4B.

Refer to FIG. 4A, which is the emission spectrum obtained by excitation of the lithium ion phosphor samples with different concentrations prepared according to Example 3 under 537 nm green light. It can be seen from the figure that the emission spectrum of the sample is mainly composed of two peaks in the wavelength range of 580nm to 640nm. These two sharp peaks are both characteristic emission peaks of Eu ³⁺ , and the strongest emission peak is at 619nm. This indicates that the sample glows red.

Refer to FIG. 4B, which is an excitation spectrum obtained by using 619 nm red light as the monitoring wavelength of a sample of lithium ion phosphors with different concentrations prepared according to Example 3. It can be seen from the figure that the excitation spectrum of the sample is mainly composed of several sharp line spectra between 350nm and 600nm, which belong to the 4f-4f transition of Eu ³⁺ , and the strongest excitation peak is the blue region with a wavelength of 465nm. As can be seen from the excitation spectra and emission spectra of the sample, the concentration of Li ⁺ incorporation is not the same, the sample emission intensity of the phosphor is also different, from the green excitation peak can be seen that when the concentration of Li ⁺ is incorporated 0.5 When, the emission intensity of the sample is relatively strongest.

Example 4

This example investigates the effect of doping different concentrations of sodium ions on the luminescence performance of red phosphors.

Referring to the preparation method of red phosphor in Example 1, when the Eu ³⁺ concentration is 0.3, sodium ions of different concentrations are doped to prepare four sets of samples Na _n Y _0.7 Eu _0.3 (MoO ₄ ) ₂ (n=0.25, 0.5, 0.75 ,1). The fluorescence spectrometer voltage is set to 400V, the slit width is 2.5nm, the scanning speed is 1200nm/min, the excitation wavelength is set to 537nm when measuring the emission spectrum, and the monitoring wavelength is set to 619nm when measuring the excitation spectrum. Use F-4600 The emission spectrum and excitation spectrum of the red phosphor obtained by the fluorescence spectrometer test are shown in Figures 5A-5B.

Refer to Figure 5A, which is the emission spectrum obtained by excitation of the sodium ion phosphor samples with different concentrations prepared according to Example 4 under 537 nm green light. It can be seen from the figure that the strongest emission peak is located at 619nm, indicating that the sample emits red light, and the strongest excitation peak is the characteristic emission peak of Eu ³⁺ .

Referring to FIG. 5B, it is an excitation spectrum obtained by using 619 nm red light as the monitoring wavelength of a sample of phosphor doped with different concentrations of sodium ion prepared according to Example 4. It can be seen from the figure that when the concentration of sodium ions is changed, the shape of the sample excitation spectrum and the position of the peak are basically unchanged. The excitation peaks in the wavelength range of 350nm to 600nm belong to the typical Eu ³⁺ 4f-4f transition, the strongest The excitation peak is located in the blue band of 465 nm, indicating that the sample can be most effectively excited by blue light. It can be seen from the excitation spectrum and emission spectrum of the sample that when the concentration of sodium ions doped with the sample phosphor is different, the luminous intensity of the sample also changes. Referring to the excitation peak of the green light band, we can see that when sodium ions are doped When the concentration is 0.25, the luminous intensity of the sample is the strongest.

Example 5

This example examines the effect of different second-stage firing temperatures on the luminescence performance of red phosphors.

With reference to the preparation method of red phosphor in Example 1, when the sample doped with alkaline metal ion is sodium ion and the Eu ³⁺ concentration is 0.3, the second stage of firing temperature is 700 ℃, 800 ℃, 900 ℃, respectively, prepared Three sets of comparative samples. The fluorescence spectrometer voltage is set to 400V, the slit width is 2.5nm, the scanning speed is 1200nm/min, the excitation wavelength is set to 537nm when measuring the emission spectrum, and the monitoring wavelength is set to 619nm when measuring the excitation spectrum. Use F-4600 The emission spectrum and excitation spectrum of the red phosphor obtained by the fluorescence spectrometer test are shown in Figure 6A-6B. The results of scanning electron microscopy analysis are shown in Figure 7A-7C.

Refer to Figure 6A, which is the emission spectrum obtained by exciting the phosphor samples prepared according to the different firing temperatures of Example 5 under 537nm green light. Refer to Figure 6B, which is the excitation spectrum of the phosphor samples prepared according to the different firing temperature of Example 5 with the red light of 619 nm as the monitoring wavelength. Spectral test results show that when the baking temperature of the sample is 800 ℃, the phosphor has the best luminescence performance. The luminescence performance of the sample phosphor decreases with the increase of annealing temperature. The reason for this phenomenon may be that the calcination temperature is too high and damaged The crystal structure of the phosphor leads to a decrease in luminous intensity.

Referring to Figures 7A-7C, which are prepared according to Example 5, the scanning electron micrographs of phosphor samples obtained at 700°C, 800°C, and 900°C firing temperatures, respectively. It can be seen from the figure that the crystal structure in the figure is relatively better. It is regular and exhibits a specific shape, indicating that the crystal is formed well.

Claims

A red phosphor, characterized in that the chemical formula of the red phosphor is M n Y 1-x Eu x (MoO 4 ) 2 , the value of x is 0.1-0.5, M is alkaline metal, and the value of n For 0.10-1.5.
The red phosphor of claim 1, wherein the value of x is 0.2-0.4.
The red phosphor of claim 1, wherein the alkaline metal is one or more of Li, Na and K.
The red phosphor of claim 1, wherein the value of n is 0.25-1.
The preparation method of the red phosphor according to any one of claims 1 to 4, characterized in that it comprises the following steps:

The compound containing lithium ion, the compound containing sodium ion, the compound containing potassium ion, the compound containing yttrium ion, and the compound containing europium ion are dissolved in nitric acid, and mixed with the compound containing molybdenum ion and organic acid to obtain a mixture solution;

Stir the obtained mixture solution to adjust the pH value;

The mixture solution after adjusting the pH value is dried, and then calcined to obtain a red phosphor.
The method for preparing a red phosphor according to claim 5, wherein the compound containing lithium ions is one or more of lithium oxide, lithium hydroxide and lithium carbonate; the compound containing sodium ions is sodium hydroxide One or more of sodium carbonate and sodium bicarbonate; the compound containing potassium ions is one or more of potassium oxide, potassium hydroxide and potassium carbonate.
The method for preparing a red phosphor according to claim 5, wherein the compound containing yttrium ions is one or more of yttrium oxide, yttrium hydroxide and yttrium carbonate; the compound containing europium ions is europium oxide, One or more of europium hydroxide and europium carbonate; the compound containing molybdenum ions is one or more of ammonium molybdate, sodium molybdate and potassium molybdate; and the organic acid is citric acid.
The method for preparing red phosphors according to claim 5, wherein the obtained mixture solution is stirred at 40-90°C for 15-60 minutes to adjust the pH value of 6.5-8.5; after adjusting the pH value The mixed solution is dried at 35-150°C for 6-36 hours; and then calcined at 300-1200°C for 2-12 hours.
The application of the red phosphor according to any one of claims 1-4, characterized in that the excitation in claims 1-4 is excited by one or more of ultraviolet light, near ultraviolet light, blue light and green light. Any one of the red phosphors obtains red light.
A light source comprising the red phosphor according to any one of claims 1 to 4 and matching LED chips.