CN113072940A

CN113072940A - Double-emission fluorescent powder for LED plant illumination and preparation method and application thereof

Info

Publication number: CN113072940A
Application number: CN202110325289.4A
Authority: CN
Inventors: 张学杰; 孙嘉敏; 雷炳富; 张浩然; 陈炜彬; 邹西坤; 庄健乐; 胡超凡; 刘应亮
Original assignee: South China Agricultural University
Current assignee: South China Agricultural University
Priority date: 2021-03-26
Filing date: 2021-03-26
Publication date: 2021-07-06

Abstract

The invention belongs to the field of luminescent materials, and discloses double-emission fluorescent powder for LED plant illumination, and a preparation method and application thereof. The chemical general formula of the fluorescent powder is K₂Ca_1‑xPO₄F:xEu²⁺yA, wherein x is more than 0 and less than or equal to 0.1; a is a cosolvent, is NH₄F、CaF₂、KF、H₃BO₃、LiF、Li₂CO₃One of (1); y is A and is synthetic K₂Ca_1‑ _xPO₄F:xEu²⁺The phosphor powder is prepared from raw materials with weight percentage of y being more than or equal to 0 and less than or equal to 5wt percent. The fluorescent powder shows the characteristic of adjustable green light and red light emission intensity according to different doping concentrations and excitation wavelengths, has larger half-peak width of double emission bands, and can be matched with the absorption of phytoalexin. The fluorescent powder can be excited by ultraviolet light and near ultraviolet light, and has higher luminescent quantum efficiency and lower luminescent thermal burstThe LED lamp has the advantages of good extinguishing performance and wide application prospect in the field of LED plant illumination.

Description

Double-emission fluorescent powder for LED plant illumination and preparation method and application thereof

Technical Field

The invention belongs to the field of luminescent materials, and particularly relates to double-emission fluorescent powder for LED plant illumination, and a preparation method and application thereof.

Background

Generally, the growth and development of plants depend on sunlight, but industrial production, tissue culture, propagation of test-tube plantlets and the like of commercial crops such as vegetables and flowers also need an artificial light source for light supplement so as to promote photosynthesis. The photosystem in which the photoreaction occurs consists of several pigments, such as chlorophyll a (chlorophyl a), chlorophyll b (chlorophyl b), carotenoids (Catotenoids), etc., with their main absorption spectra centered at 450nm and 660 nm.

Therefore, in order to promote photosynthesis, two schemes are mainly adopted for light supplement: (1) the plant lighting device is constructed by adopting the blue light LED of 450nm and the red light LED of 660nm, however, the scheme has the problems of high cost, low lighting effect, complex device structure and the like; (2) the technology for converting the blue light LED chip and the red fluorescent powder has the advantages of simplicity in preparation, high luminous efficiency, low cost and the like, but the blue light LED chip is narrow in half-peak width (30 nm) of an emission band and low in matching property with a plant absorption spectrum.

In addition, in order to be able to perceive and respond to changes in the light intensity, light quality, light direction and light cycle of the surrounding environment, plants have evolved a photoreceptive system (photoreceptor). The photoreceptor is the key of the plant to sense the external environment change, and in the plant light reaction, the most important photoreceptor is the photosensitizing pigment (phytochrome) absorbing red light/far-red light. The photosensitive pigment is a kind of pigment protein which has reversal effect on red light and far-red light absorption, participates in photomorphogenesis and regulates plant development, is extremely sensitive to red light (R) and far-red light (FR), and plays an important regulation role in the whole growth and development process from germination to maturity of plants. Phytochromes in plants exist in two more stable states: red light absorption type (Pr) and far-red light absorption type (Pfr), which can be reversed mutually under irradiation of red light and far-red light. The research results related to phytochrome show that the effects of phytochrome (Pr, Pfr) on plant morphology comprise seed germination, de-yellowing, stem elongation, leaf expansion, shade-avoidance, flowering induction and the like. However, the traditional LED plant lighting schemes only aim at photosynthesis, neglecting the role of far-red light in plant morphogenesis.

In conclusion, it is very important how to prepare a full-spectrum (blue light + red light + far-red light) plant lighting device excited by ultraviolet and near-ultraviolet.

Disclosure of Invention

In order to solve the technical problems, the invention mainly aims to provide the dual-emission fluorescent powder for LED plant illumination.

The invention also aims to provide a preparation method of the double-emission fluorescent powder for LED plant illumination.

The invention further aims to provide application of the double-emission fluorescent powder for LED plant illumination in the field of plant illumination.

The purpose of the invention is realized by the following technical scheme:

a dual-emission fluorescent powder for LED plant illumination has a chemical general formula of K₂Ca_1-xPO₄F:xEu²⁺yA, wherein x is more than 0 and less than or equal to 0.1; a is a cosolvent, is NH₄F、CaF₂、KF、H₃BO₃、LiF、Li₂CO₃One of (1); y is A and is synthetic K₂Ca_1-xPO₄F:xEu²⁺The phosphor powder is prepared from raw materials with weight percentage of y being more than or equal to 0 and less than or equal to 5wt percent.

The preparation method of the double-emission fluorescent powder for LED plant illumination is characterized by comprising the following steps of:

s1, taking a K-containing compound, a Ca-containing compound, a P-containing compound, a F-containing compound, an Eu-containing compound and a cosolvent as raw materials, weighing the raw materials according to the chemical general formula, and uniformly mixing the raw materials;

s2, calcining the uniformly mixed raw materials in the step S1 in a reducing atmosphere, cooling to room temperature, taking out, and grinding to obtain the dual-emission fluorescent powder for LED plant illumination.

The K-containing compound described in step S1 is K₂CO₃、KF、KH₂PO₄More than one of them.

The Ca-containing compound in the step S1 is CaCO₃、CaF₂More than one of them.

The P-containing compound described in step S1 is NH₄H₂PO₄、KH₂PO₄More than one of them.

The F-containing compound in the step S1 is CaF₂And KF.

The Eu compound in step S1 is Eu₂O₃、EuF₃More than one of them.

The reducing atmosphere described in step S2 is N₂And H₂Mixed gas of which H₂The volume percentage of the mixed gas is 5-20%.

The calcination temperature in the step S2 is 900-1100 ℃, and the calcination time is 4-10 h.

The application of the double-emission fluorescent powder for LED plant illumination in the field of LED plant illumination can be used for packaging an LED plant illumination device with an ultraviolet or near-ultraviolet LED chip, and the device emission spectrum can cover blue light, red light and far-red light regions due to the wide half-peak width of a red light emission band.

Compared with the prior art, the invention has the following advantages and beneficial effects:

(1) by adjusting the doping concentration of Eu ions, the blue light emission intensity and the red light emission intensity can be controllably adjusted, and further, fluorescent powder with different blue light and red light ratios can be obtained;

(2) the dual-emission fluorescent powder is excited by changing different excitation wavelengths, and the blue light emission intensity and the red light emission intensity can be regulated and controlled;

(3) the double-emission fluorescent powder for LED plant illumination provided by the invention has higher luminous quantum efficiency, and the optimized internal quantum efficiency is about 55-95%, and the optimized external quantum efficiency is about 40-80%;

(4) the double-emission fluorescent powder for LED plant illumination provided by the invention has low luminescence thermal quenching performance, and almost no quenching exists in luminescence at 150 ℃;

(5) the double-emission fluorescent powder for LED plant illumination provided by the invention can be effectively excited by an ultraviolet or near-ultraviolet LED chip, and due to the fact that the red light emission band is wide, the LED plant illumination device can provide blue light, red light and far-red light at the same time.

Drawings

FIG. 1 is an XRD spectrum of the dual emission phosphor of example 1;

FIG. 2 is an excitation and emission spectrum of the dual emission phosphor of example 1;

FIG. 3 is the emission spectra of dual emission phosphors of example 2 with different Eu doping concentrations;

FIG. 4 is the emission spectra of the dual emission phosphor of example 2 at different excitation wavelengths;

FIG. 5 is a graph showing the decay of the fluorescence lifetime of the dual emission phosphor of example 3;

FIG. 6 is a temperature-variable spectrum of a dual emission phosphor of example 4;

FIG. 7 is a diagram illustrating the application of the dual emission phosphor of example 5 in an LED plant lighting device;

Detailed Description

The present invention will be further described with reference to the following specific examples and drawings, which are not intended to limit the invention in any manner. Reagents, methods and apparatus used in the present invention are conventional in the art unless otherwise indicated.

Unless otherwise indicated, reagents and materials used in the present invention are commercially available.

Example 1:

the double hair obtained in this exampleThe chemical composition of the emitting phosphor is K₂Ca_0.99PO₄F:0.01Eu²⁺,3wt％H₃BO₃。

TABLE 1 raw material composition of dual emission phosphor in example 1

Raw materials	CaCO₃	CaF₂	KH₂PO₄	K₂CO₃	Eu₂O₃	H₃BO₃
							Quality (g)	0.9416	0.7496	2.6128	1.3268	0.0338	0.1699

Analytically pure calcium carbonate (CaCO) is precisely weighed according to Table 1₃) Calcium fluoride (CaF)₂) Potassium dihydrogen phosphate (KH)₂PO₄) Europium oxide (Eu)₂O₃) Boric acid(H₃BO₃). The raw materials which are accurately weighed are placed in an agate mortar for full grinding, are placed in a corundum crucible after being uniformly mixed, and are transferred to a tubular furnace, and the volume fractions of the materials are respectively 5 percent and 95 percent of H₂And N₂Sintering for 6h in a 960 ℃ tubular furnace under a mixed reducing atmosphere, cooling to room temperature along with the furnace, and grinding to obtain the dual-emission fluorescent powder sample. FIG. 1 shows the XRD pattern of the sample corresponding to example 1, and it can be seen that the X-ray diffraction peak and K of the obtained product₂CaPO₄And F, matching standard cards. The emission spectrum of the sample shows dual emission characteristics under the excitation of 330nm, the main emission peaks are respectively located at 480nm and 660nm, and the half-peak widths of the emission bands are respectively 69nm and 142 nm. Different excitation spectra were obtained by monitoring 480nm and 660nm (as shown in FIG. 2).

Example 2:

the chemical compositions of the dual-emission fluorescent powder obtained in the embodiment are respectively K₂Ca_(1-x)PO₄F:xEu²⁺,5wt％NH₄F(x＝0.002；0.004；0.008；0.015；0.020)。

Table 2 different Eu in example 2²⁺Raw material composition of doping concentration dual-emission fluorescent powder

Analytically pure potassium carbonate (K) is weighed precisely as in Table 2₂CO₃) Potassium fluoride (KF), calcium carbonate (CaCO)₃) Ammonium dihydrogen phosphate (NH)₄H₂PO₄) Europium oxide (Eu)₂O₃) Ammonium fluoride (NH)₄F) In that respect The raw materials which are accurately weighed are placed in an agate mortar for full grinding, are placed in a corundum crucible after being uniformly mixed, and are transferred to a tubular furnace, and the volume fractions of the materials are respectively 10 percent and 90 percent of H₂And N₂Sintering the mixture in a 1000 ℃ tube furnace for 8 hours under a mixed reducing atmosphere, cooling the mixture to room temperature along with the furnace, and grinding the mixture to obtain the dual-emission fluorescent powder sample. FIG. 3 shows the emission spectra of samples with different Eu doping concentrations under 330nm excitation, from which it can be seen that the low-concentration doped samples have stronger bluish lightThe red light of the high-concentration doped sample is stronger, and the obvious concentration dependence characteristic is presented. And the obtained fluorescent powder can obtain different light colors under the excitation of different wavelengths (as shown in figure 4).

Example 3:

the chemical composition of the dual-emission fluorescent powder obtained in the embodiment is K₂Ca_0.995PO₄F:0.005Eu²⁺,8wt％LiF。

Table 3 raw material composition of dual emission phosphor in example 3

Raw materials	CaCO₃	CaF₂	KH₂PO₄	K₂CO₃	EuF₃	LiF
							Quality (g)	0.9512	0.7496	2.6128	1.3268	0.0201	0.4528

Analytically pure calcium carbonate (CaCO) was weighed precisely as shown in Table 3₃) Calcium fluoride (CaF)₂) Potassium dihydrogen phosphate (KH)₂PO₄) Potassium carbonate (K)₂CO₃) Europium fluoride (EuF)₃) Lithium fluoride (LiF). The raw materials which are accurately weighed are placed in an agate mortar for full grinding, are placed in a corundum crucible after being uniformly mixed, and are transferred to a tubular furnace, and the volume fractions of the materials are respectively 20 percent and 80 percent of H₂And N₂Sintering the mixture in a 1050 ℃ tubular furnace for 4 hours under a mixed reducing atmosphere, cooling the mixture to room temperature along with the furnace, and grinding the mixture to obtain the dual-emission fluorescent powder sample. As can be seen from the laser confocal imaging excited by 405nm, the dual-emission fluorescent powder is composed of light-emitting particles with different light colors, and the cyan light-emitting particles and the red light-emitting particles are relatively independent. Further testing the fluorescence lifetimes of the cyan and red lights is shown in FIG. 5, where it can be seen that the difference in lifetimes between the two lights is large, originating from different luminescence centers.

Example 4:

the chemical composition of the dual-emission fluorescent powder obtained in the embodiment is K₂Ca_0.99PO₄F:0.01Eu²⁺。

Table 4 raw material composition of dual emission phosphor in example 4

Raw materials	K₂CO₃	KF	CaCO₃	CaF₂	NH₄H₂PO₄	Eu₂O₃
							Quality (g)	1.3267	1.1155	0.9416	0.7496	2.2085	0.0338

Analytically pure potassium carbonate (K) is weighed precisely as in Table 4₂CO₃) Potassium fluoride (KF), calcium carbonate (CaCO)₃) Calcium fluoride (CaF)₂) Ammonium dihydrogen phosphate (NH)₄H₂PO₄) Europium oxide (Eu)₂O₃). The raw materials which are accurately weighed are placed in an agate mortar for full grinding, are placed in a corundum crucible after being uniformly mixed, and are transferred to a tubular furnace, and the volume fractions of the materials are respectively 5 percent and 95 percent of H₂And N₂Sintering the mixture in a 950 ℃ tubular furnace for 10 hours in a mixed reducing atmosphere, cooling the mixture to room temperature along with the furnace, and grinding the mixture to obtain the dual-emission fluorescent powder sample. The temperature-variable spectrum of the phosphor tested under 330nm excitation is shown in FIG. 6, and it can be seen from the graph that the phosphor has almost no luminescence quenching at 150 ℃ and shows excellent luminescence thermal stability.

Example 5:

the chemical composition of the dual-emission fluorescent powder obtained in the embodiment is K₂Ca_0.996PO₄F:0.004Eu²⁺,4wt％H₃BO₃。

TABLE 5 raw material composition of dual emitting phosphor in example 5

Raw materials	CaCO₃	CaF₂	KH₂PO₄	KF	Eu₂O₃	H₃BO₃
							Quality (g)	0.9531	0.7496	2.6128	0.5577	0.0135	0.1955

Analytically pure calcium carbonate (CaCO) was weighed precisely as in Table 5₃) Calcium fluoride (CaF)₂) Potassium dihydrogen phosphate (KH)₂PO₄) Potassium fluoride (KF), europium oxide (Eu)₂O₃) Boric acid (H)₃BO₃). The raw materials which are accurately weighed are placed in an agate mortar for full grinding, are placed in a corundum crucible after being uniformly mixed, and are transferred to a tubular furnace, and the volume fractions of the materials are respectively 10 percent and 90 percent of H₂And N₂N₂Sintering the mixture in a 1100 ℃ tube furnace for 5 hours in a mixed reducing atmosphere, cooling the mixture to room temperature along with the furnace, and grinding the mixture to obtain the dual-emission fluorescent powder sample. 380nm LED chip and sample packaged LED plant illuminationThe emission spectrum of the light device is shown in fig. 7, and due to the fact that the red light spectral band is wide, the light device can meet the spectral requirements of plants in blue light, red light and far red light regions.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.

Claims

1. The double-emission fluorescent powder for LED plant illumination is characterized in that: the chemical general formula of the fluorescent powder is K₂Ca_1-xPO₄F:xEu²⁺yA, wherein x is more than 0 and less than or equal to 0.1; a is a cosolvent, is NH₄F、CaF₂、KF、H₃BO₃、LiF、Li₂CO₃One of (1); y is A and is synthetic K₂Ca_1-xPO₄F:xEu²⁺The phosphor powder is prepared from raw materials with weight percentage of y being more than or equal to 0 and less than or equal to 5wt percent.

2. The preparation method of the double-emission fluorescent powder for LED plant lighting according to claim 1, characterized by comprising the following steps:

s1, weighing raw materials and uniformly mixing the raw materials by using a K-containing compound, a Ca-containing compound, a P-containing compound, a F-containing compound, an Eu-containing compound and a cosolvent according to the chemical general formula of claim 1;

3. The method of claim 2, wherein: the K-containing compound described in step S1 is K₂CO₃、KF、KH₂PO₄More than one of them.

4. According to claim2, the preparation method is characterized in that: the Ca-containing compound in the step S1 is CaCO₃、CaF₂More than one of them.

5. The method of claim 2, wherein: the P-containing compound described in step S1 is NH₄H₂PO₄、KH₂PO₄More than one of them.

6. The method of claim 2, wherein: the F-containing compound in the step S1 is CaF₂And KF.

7. The method of claim 2, wherein: the Eu compound in step S1 is Eu₂O₃、EuF₃More than one of them.

8. The method of claim 2, wherein: the reducing atmosphere described in step S2 is N₂And H₂Mixed gas of which H₂The volume percentage of the mixed gas is 5-20%.

9. The method of claim 2, wherein: the calcination temperature in the step S2 is 900-1100 ℃, and the calcination time is 4-10 h.

10. The use of the dual-emitting phosphor for LED plant lighting of claim 1 in the field of LED plant lighting.