Sr < 2 + >-doped CaAl12O19: Cr < 3 + > dark red fluorescent powder and preparation method thereof

Abstract

The invention discloses Sr < 2 + >-doped CaAl12O19: Cr < 3 + > dark red fluorescent powder and a preparation method thereof, the fluorescent powder takes Ca1-ySryAl12O19 as a matrix and doped trivalent chromium ions (Cr < 3 + >) as a luminescence center, and the doping concentration of Sr < 2 + > is 0-90 mol%. The excitation spectrum of the fluorescent powder shows two characteristic broadband of Cr < 3 + > ions, which are respectively located at 418 nm and 580 nm, the main excitation peak is located at 418 nm, and the emission spectrum of the fluorescent powder is broadband red light emission of about 685 nm. The fluorescent powder can effectively emit red light with the wavelength ranging from 680 nm to 700 nm under excitation of ultraviolet light with the wave band ranging from 350 nm to 450 nm. By regulating and controlling the doping proportion of Sr, when the doping mole fraction of Sr < 2 + > is 0.7 (namely y is equal to 0.7), the fluorescence performance is optimal, and the emission intensity is remarkably enhanced. Therefore, the fluorescent powder Ca1-ySryAl12O19: Cr < 3 + > has a good application prospect in the field of plant light supplement.

Description

Technical Field

[0001] This invention relates to the field of inorganic luminescent materials technology, specifically to an aluminate-based phosphor and its preparation method, and more particularly to a red phosphor that can be used for supplemental lighting in plants and its preparation method. Background Technology

[0002] During plant growth, phytochromes play a crucial role in promoting seed germination, reducing yellowing, and leaf development. Phytochromes exist primarily in two forms: red-light-absorbing pigments (Pr), which mainly absorb red light in the 600-700 nm wavelength range; and far-red-light-absorbing pigments (Pfr), whose absorption spectrum is mainly in the 650-780 nm band. These two pigments can interconvert under different wavelengths of light, synergistically regulating plant growth.

[0003] In addition, plant photosynthesis relies on three main photosynthetic pigments: chlorophyll a (primarily absorbing light in the 350-450nm and 600-680nm wavelength range), chlorophyll b (absorbing light in the 400-500nm and 610-650nm wavelength range), and carotenoids (absorbing light in the 400-500nm wavelength range). Therefore, in modern facility agriculture, to improve plant photosynthetic efficiency and crop yield, it is necessary to supplement light sources with wavelength distributions that match the plant's needs. Especially under conditions of insufficient light or at night, LED plant lights are widely used as a new generation of energy-saving supplemental lighting equipment.

[0004] In recent years, red phosphors have become a key material in LED light sources for plant supplemental lighting. Their emission wavelength closely matches the absorption of red light by plants, effectively promoting flowering and fruit formation. Currently, commonly used red phosphors are mostly nitride or silicate systems. While they have high luminous efficiency, they suffer from harsh synthesis conditions, poor thermal stability, and hygroscopicity, limiting their application in complex environments. In contrast, aluminate-based red phosphors, due to their stable structure, good heat resistance, and stable chemical properties, have become highly promising luminescent materials for plant lighting. Among them, trivalent chromium ions (Cr...) are particularly promising. 3+ Doped aluminate systems, under near-ultraviolet or blue light excitation (such as λ), ex =430-470nm) can produce strong red light emission with wavelengths between 650-720nm, which highly matches the red light absorption window of plant growth. Cr 3 The luminescence process of ions mainly involves their transformation from the ground state in an octahedral crystal field. 4 A2 transitions to the excited state. 4 T2, 4 T1, and occurred 4 T2→ 4 The radiative transition of A2 emits deep red light. In a suitable crystal field environment, Cr... 3+It can achieve high luminous intensity and thermal stability. Meanwhile, due to Cr... 3+ As ions with stable charge and a single valence state, their doping concentration and the design of the energy level structure of the luminescent center are highly controllable.

[0005] Therefore, a Cr-based 3+ The novel red phosphor material with doped and modified aluminate structure can not only solve the problems of poor thermal stability and narrow applicable wavelength range of existing red phosphor materials, but also provide a more efficient and environmentally friendly luminescent material for plant supplemental LEDs, which has important research significance and broad application prospects. Summary of the Invention

[0006] This invention provides a Cr-based 3 The doped modified calcium aluminate red phosphor and its preparation method are used to solve the problems of low red light emission efficiency and poor thermal stability of fluorescent materials used for plant supplemental lighting.

[0007] This invention first provides a Cr 3+ A red phosphor doped with calcium aluminate, the chemical formula of which is: Ca 1- y Sr y Al 12 O 19 0.07Cr 3+ In the formula, 10at% ≤ y ≤ 90at%.

[0008] The present invention also provides a Cr 3+ The preparation method of doped red phosphor, the preparation steps are as follows:

[0009] Step 1: Weigh the raw materials CaO, Al2O3, Cr2O3, and SrCO3 according to the element molar ratio, where y = 0.1, 0.3, 0.5, 0.7, and 0.9. Weigh the required raw materials, including calcium-containing compounds, aluminum-containing compounds, chromium-containing compounds, and strontium-containing compounds, wherein the mass ratio of specific components meets the target molar ratio.

[0010] Step 2: Grind the raw materials weighed in Step 1 thoroughly and evenly, and transfer them to a crucible. Perform high-temperature sintering treatment in air atmosphere. The sintering temperature is 1300-1500℃ and the sintering time is 4-6 hours.

[0011] Step 3: After sintering, allow the sample to cool naturally to room temperature, remove the sample, and grind it evenly to finally obtain Cr. 3+ Doped Ca 1-y Sr y Al 12 O 19 Red fluorescent powder.

[0012] In the site selection and step one, the strontium-containing compound is strontium carbonate, strontium oxide, strontium chloride, or strontium nitrate.

[0013] Preferably, in step one, the chromium-containing compound is chromium trioxide (Cr2O3), ammonium chromate, or potassium chromate.

[0014] Preferably, in step one, the calcium-containing compound is calcium oxide, calcium carbonate, or calcium chloride.

[0015] Preferably, in step one, the aluminum-containing compound is aluminum oxide, aluminum sulfate, or aluminum chloride.

[0016] Preferably, in step one, Cr 3+ The doping ratio is 0.07 moles.

[0017] Preferably, in step one, Sr 2+ The doping ratio ranges from 0.1 to 0.9 moles.

[0018] Preferably, in step one, the excess of the aluminum-containing compound can be controlled within the range of 1%-2%.

[0019] Preferably, in step two, the sintering temperature is 1300-1500℃;

[0020] Preferably, in step two, the sintering time is 4-6 hours.

[0021] The Ca obtained by this invention 1-y Sr y Al 12 O 19 0.07Cr 3+ Phosphors exhibit a strong red emission peak under near-ultraviolet (360-420 nm) or blue light (420-480 nm) excitation, with the peak position between 670-700 nm, especially at λ. em It exhibits high gamma-ray emission around 685nm, which can effectively match the absorption requirements of plant chlorophyll for red light.

[0022] Compared to existing red phosphors such as nitride and silicate materials, the Cr described in this invention... 3+ Doped aluminate phosphors have the following advantages:

[0023] The synthesis process is simple, and the raw materials are widely available;

[0024] Excellent thermal and chemical stability;

[0025] It enables mass production and is suitable for industrial applications;

[0026] The emission wavelength is matched to the absorption region of plant phytochromes;

[0027] It is heat resistant and not easily hydrolyzed, making it suitable for plant LED supplemental lighting systems in various environments.

[0028] This invention first provides a Cr 3+ The doped red phosphor has the chemical formula: Ca 1- y Sr y Al 12 O 19 0.07Cr 3+ In the formula, 10at% ≤ y ≤ 90at%. The phosphor is Cr... 3+ It is a light-emitting ion that achieves ultraviolet light absorption and red light emission, and is used as a red light source for matching ultraviolet LEDs, suitable for light-emitting fields such as plant supplemental lighting. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 The Ca obtained in Example 1 1-y Sr y Al 12 O 19 0.07Cr 3+ XRD pattern of red phosphor.

[0031] Figure 2 The Ca obtained in Example 1 1-y Sr y Al 12 O 19 0.07Cr 3+ Excitation spectrum of red phosphor.

[0032] Figure 3 The Ca obtained in Example 1 1-y Sr y Al 12 O 19 0.07Cr 3+ Emission spectrum of red phosphor.

[0033] Figure 4 The Ca obtained in Examples 1, 2, 3, 4, and 5 1-y Sr y Al 12 O 19 0.07Cr 3++The emission spectrum. Detailed Implementation

[0034] The red fluorescent powder has the chemical formula Ca. 1-y Sr y Al 12 O 19 0.07Cr 3+ In the formula, 10at% ≤ y ≤ 90at%, the following detailed explanation is provided with reference to specific embodiments:

[0035] Example 1

[0036] Calcium carbonate, aluminum oxide, chromium oxide, and strontium carbonate were selected as starting materials, and the mixture was processed according to the chemical formula Ca... 1-y Sr y Al 12 O 19 0.07Cr 3+ The molar ratio of each element in the sample Ca:Sr:Al:Cr is (1-y):y:(12-x):x, corresponding to y=0.9 and x=0.07 respectively. Four raw materials were weighed, with 2% excess alumina. The samples were ground in a corundum mortar for 30 minutes. The thoroughly mixed sample was transferred to an alumina crucible and then transferred to a high-temperature furnace. It was pre-calcined at 900℃ in air for 2 hours, and then calcined at 1500℃ in air for 6 hours. After the furnace temperature dropped to room temperature, the sample was taken out and ground evenly to obtain a Cr-containing sample. 3+ The doped red phosphor has the composition Ca. 0.1 Sr 0.9 Al 12 O 19 0.07Cr 3+ .

[0037] Figure 1 The Ca obtained in Example 1 0.3 Sr 0.7 Al 12 O 19 0.07Cr 3+ The XRD pattern shows that the spectrum is similar to that of CaAl. 12 O 19 Consistent with this, it proves that Ca was successfully prepared. 0.3 Sr 0.7 Al 12 O 19 0.07Cr 3+ Fluorescent powder. Figure 2 The Ca obtained in Example 1 under 685nm monitoring 0.3 Sr 0.7 Al 12 O 19 0.07Cr3+ The excitation spectrum of the red phosphor, from Figure 2 It can be seen that the laser spectrum of this phosphor is Cr 3+ The two characteristic broadbands are located at 350nm-475nm and 500nm-625nm, respectively, with the strongest peak at 418nm. Figure 3 The Ca obtained in Example 1 0.3 Sr 0.7 Al 12 O 19 0.07Cr 3+ The emission spectrum of the phosphor, from Figure 3 It can be seen that the emission spectrum of this red phosphor excited by 418 nm light is Cr 3+ It has a bandwidth of 650nm-725nm, with the strongest peak located at 685nm.

[0038] Example 2

[0039] Calcium carbonate, aluminum oxide, chromium oxide, and strontium carbonate were selected as starting materials, and the mixture was processed according to the chemical formula Ca... 1-y Sr y Al 12 O 19 0.07Cr 3+ The molar ratio of each element in the sample Ca:Sr:Al:Cr is (1-y):y:(12-x):x, corresponding to y=0.7 and x=0.07. Four raw materials were weighed, with 2% excess alumina. The samples were ground in a corundum mortar for 30 minutes. The thoroughly mixed sample was transferred to an alumina crucible, which was then placed in a high-temperature furnace and calcined at 900℃ in air for 2 hours for pre-calcination. The temperature was then increased to 1500℃ and calcined in air for 6 hours. After the furnace temperature cooled to room temperature, the sample was removed and ground evenly to obtain a Cr-containing sample. 3+ The doped red phosphor has the composition Ca. 0.3 Sr 0.7 Al 12 O 19 0.07Cr 3+ The spectral properties of this phosphor are similar to those of Example 1.

[0040] Example 3

[0041] Calcium carbonate, aluminum oxide, chromium oxide, and strontium carbonate were selected as starting materials, and the mixture was processed according to the chemical formula Ca... 1-y Sr y Al 12 O 19 0.07Cr 3+The molar ratio of each element in the sample Ca:Sr:Al:Cr is (1-y):y:(12-x):x, corresponding to y=0.5 and x=0.07. Four raw materials were weighed, with 2% excess alumina. The samples were ground in a corundum mortar for 30 minutes. The thoroughly mixed sample was transferred to an alumina crucible, which was then placed in a high-temperature furnace and calcined at 900℃ in air for 2 hours for pre-calcination. The temperature was then increased to 1500℃ and calcined in air for 6 hours. After the furnace temperature cooled to room temperature, the sample was removed and ground evenly to obtain a Cr... 3+ The doped red phosphor has the composition Ca. 0.5 Sr 0.5 Al 12 O 19 0.07Cr 3+ The spectral properties of this phosphor are similar to those of Example 1.

[0042] Example 4

[0043] Calcium carbonate, aluminum oxide, chromium oxide, and strontium carbonate were selected as starting materials, and the mixture was processed according to the chemical formula Ca... 1-y Sr y Al 12 O 19 0.07Cr 3+ The molar ratio of each element in the sample Ca:Sr:Al:Cr is (1-y):y:(12-x):x, corresponding to y=0.3 and x=0.07. Four raw materials were weighed, with 2% excess alumina. The samples were ground in a corundum mortar for 30 minutes. The thoroughly mixed sample was transferred to an alumina crucible, which was then placed in a high-temperature furnace and calcined at 900℃ in air for 2 hours for pre-calcination. The temperature was then increased to 1500℃ and calcined in air for 6 hours. After the furnace temperature cooled to room temperature, the sample was removed and ground evenly to obtain a Cr-containing sample. 3+ The doped red phosphor has the composition Ca. 0.7 Sr 0.3 Al 12 O 19 0.07Cr 3+ The spectral properties of this phosphor are similar to those of Example 1.

[0044] Example 5

[0045] Calcium carbonate, aluminum oxide, chromium oxide, and strontium carbonate were selected as starting materials, and the mixture was processed according to the chemical formula Ca... 1-y Sr y Al 12 O 19 0.07Cr 3+The molar ratio of each element in the sample Ca:Sr:Al:Cr is (1-y):y:(12-x):x, corresponding to y=0.1 and x=0.07. Four raw materials were weighed, with 2% excess alumina. The samples were ground in a corundum mortar for 30 minutes. The thoroughly mixed sample was transferred to an alumina crucible, which was then placed in a high-temperature furnace and calcined at 900℃ in air for 2 hours for pre-calcination. The temperature was then increased to 1500℃ and calcined in air for 6 hours. After the furnace temperature cooled to room temperature, the sample was removed and ground evenly to obtain a Cr-containing sample. 3+ The doped red phosphor has the composition Ca. 0.9 Sr 0.1 Al 12 O 19 0.07Cr 3+ The spectral properties of this phosphor are similar to those of Example 1.

[0046] Figure 4 The Ca obtained in Examples 1, 2, 3, 4, and 5 1-y Sr y Al 12 O 19 0.07Cr 3+ The emission spectrum, by Figure 4 It can be seen that the peak shape and position of all samples remained unchanged, while the luminescence intensity increased with Cr. 3+ The concentration initially increases and then decreases with increasing Cr. 3 + When the doping concentration is 7%, and Sr 2+ Ca with a doping concentration of 70% 1-y Sr y Al 12 O 19 0.07Cr 3+ The emission peak intensity reaches its highest level, and the emission peak intensity is higher than that of CaAl. 12 O 19 0.07Cr 3+ The emission peak intensity of Sr continues to increase 2+ The luminescence intensity will decrease with increasing concentration. This is because decreased structural stability and an increase in non-radiative channels become the dominant factors, leading to a decrease in luminescence intensity.

[0047] The above embodiments are only used to explain the method of the present invention. In particular, it should be noted that those skilled in the art can make appropriate improvements and modifications to the present invention without departing from the principles of the present invention, and such improvements and modifications are also within the protection scope of the claims of the present invention.

Claims

1. A red phosphor for supplemental lighting of plants and its preparation method, characterized in that, Includes the following steps: Step 1: According to the elemental molar ratio Ca:Sr:Al:Cr=(1-y):y:(12-x):x, where 10at%≤y≤90at%, x is Cr 3+ The optimal mole fraction of doping is 0.07, and y is Sr. 2+ The required raw materials, including calcium-containing compounds, strontium-containing compounds, aluminum-containing compounds, and chromium-containing compounds, are weighed according to the doping molar fraction. An appropriate excess of aluminum source is used to compensate for possible volatilization losses during the high-temperature solid-state reaction. Step 2: Grind the raw materials weighed in Step 1 thoroughly and evenly, and transfer them to a corundum crucible for high-temperature calcination in air atmosphere at a temperature of 1300-1500℃ for 4-6 hours. Step 3: After the high-temperature furnace cools to room temperature, remove the sample and grind it evenly until the red phosphor Ca is obtained. 1- y Sr y Al 12 O 19 0.07Cr 3+ .

2. The above-mentioned Cr 3 A method for preparing doped red phosphor, characterized in that, In step one, the calcium-containing compound is a calcium oxide, calcium chloride, calcium carbonate, or calcium hydroxide, etc.

3. The above-mentioned Cr 3 A method for preparing doped red phosphor, characterized in that, In step one, the aluminum-containing compound is an aluminum oxide, an aluminum chloride, an aluminum nitrate, or an aluminum hydroxide, etc.

4. The above-mentioned Cr 3 A method for preparing doped red phosphor, characterized in that, In step one, the chromium-containing compound is a chromium oxide, a chromium chloride, a chromium sulfate, or a chromium nitrate, etc.

5. The above-mentioned Cr 3 A method for preparing doped red phosphor, characterized in that, In step one, the strontium-containing compound is a strontium oxide, a strontium carbonate, a strontium chloride, or a strontium nitrate, etc.

6. The above-mentioned Cr 3 A method for preparing doped red phosphor, characterized in that, In step one, the excess of the strontium-containing compound ranges from 10% to 90%.

7. The above-mentioned Cr 3 A method for preparing doped red phosphor, characterized in that, In step two, the roasting temperature is 1300-1500℃.

8. The above-mentioned Cr 3 A method for preparing doped red phosphor, characterized in that, In step two, the roasting time is 4-6 hours.

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