A red luminescent material and its preparation method and application

Abstract

The present invention relates to the technical field of luminescent materials, and specifically discloses a red luminescent material, a preparation method thereof, and an application thereof. The red luminescent material uses titanate as a matrix and Eu as a doping element, and its chemical general formula is Na2TiO3:xEu 3+ , where 0.0125 ≤ x ≤ 0.05. The red luminescent material is an europium-doped titanate material excited by near-ultraviolet light, and has the advantages of high luminous intensity, stable luminous efficiency, and low preparation cost. The wavelength range of the red luminescent material is relatively wide, and the LED lamp prepared by using the red luminescent material can meet the needs of plant growth. The present invention effectively solves the problems of high preparation cost, low luminous intensity, and unstable luminous efficiency of the red light materials used in existing plant growth LED lamps.

Description

Technical Field

[0001] The invention relates to the technical field of luminescent materials, and specifically discloses a red luminescent material and a preparation method and application thereof. Background Art

[0002] With the continuous advancement of modern science and technology, the demand for new luminescent materials in the fields of optoelectronic devices, display technology and lighting is increasing. Especially in the field of near-ultraviolet (NUV) excited luminescent materials, red luminescent materials with broad application prospects have become a hot topic of research. The application of red luminescent materials in optoelectronic devices usually requires the irradiation of excitation light sources to make the materials emit light, and ultraviolet and near-ultraviolet light sources can provide sufficient excitation energy due to their higher energy and shorter wavelengths to excite the luminescent ions or matrices in the materials to produce fluorescence effects. Compared with traditional visible light excited materials, red luminescent materials excited by near-ultraviolet light have significant advantages in excitation efficiency, luminous intensity, color saturation, etc., so they have important application value in the fields of LED, laser display, sensor, optical communication, etc., especially in LED lighting and display technology, their excellent light color conversion characteristics make them an indispensable key component.

[0003] LED lights for plant growth are based on the spectrum required by plant photosynthesis and are composed of LED light-emitting diodes of specific wavelengths. Among them, red light and blue light are the light most absorbed by plant photosynthesis. LED lights meet the growth needs of plants by accurately providing these two types of light, promoting their photosynthesis, thereby affecting the growth and development process of plants. At present, the red light materials commonly used in plant growth LED lights are mainly aluminum indium gallium phosphide and gallium nitride-based red light epitaxial wafers. However, the production process of aluminum indium gallium phosphide is complex, the cost is high, and the wavelength range is relatively narrow. It is difficult to cover all the wavelength ranges required for plants to absorb red light. At high current density, the luminous efficiency may drop significantly. The preparation cost of gallium nitride-based red light epitaxial wafers is high, the production is difficult, and the luminous efficiency is not as good as aluminum indium gallium phosphide.

[0004] Based on this, developing a red light material with high luminous efficiency, simple preparation process and low cost has important practical significance for the development of plant growth LED lamps. Summary of the invention

[0005] In view of the problems that the red light materials used in existing plant growth LED lamps have high preparation costs, low luminous intensity and unstable luminous efficiency, the present invention provides a red light-emitting material and its preparation method and application. The chemical formula of the red light-emitting material is Na2TiO3:xEu 3+, 0.0125≤x≤0.05, is a europium-doped titanate material excited by near-ultraviolet light, which has the advantages of high luminous intensity, stable luminous efficiency and low preparation cost. More importantly, the wavelength range of the red luminescent material is wide, and the LED lamp prepared using the red luminescent material can meet the needs of plant growth.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The first aspect of the present invention provides a red luminescent material, the general chemical formula of which is Na2TiO3:xEu 3+ , 0.0125≤x≤0.05.

[0008] Compared with the prior art, the present invention uses sodium titanate as the substrate and dopes europium ions to produce a near-ultraviolet light-excited red luminescent material. Eu replaces part of the Ti position in the matrix, causing the crystal structure to change but not significantly distorted. The crystal structure of titanate is used to provide a specific crystal field for europium ions. The symmetry and strength of the crystal field will affect the energy level splitting and transition probability of europium ions. When the titanate matrix absorbs energy, it can transfer energy to the doped europium ions, causing the europium ions to be excited to a higher energy level. However, the europium ions in the excited state are unstable and will transition to a lower energy level. Among them, Eu 3+ of 5 D0→ 7 The F2 transition leads to a strong emission peak at 614nm; Eu 3+ of 5 D0→ 7 The F4 transition leads to a secondary strong emission peak at 703nm; this band is a specific wavelength absorption band for chlorophyll synthesis in plant growth, which is of great significance for plant growth. The red luminescent material provided by the present invention has the advantages of high luminous intensity, stable luminous efficiency and low preparation cost, which effectively solves the problems of high preparation cost, low luminous intensity and unstable luminous efficiency of the red light materials used in plant growth LED lamps in the prior art.

[0009] Preferably, the red light-emitting material is a trigonal crystal system having an R-3 (148) space group structure.

[0010] The second aspect of the present invention provides a method for preparing the red luminescent material, comprising the following steps:

[0011] Step 1: weigh a sodium source, a titanium source and a europium source according to the designed ratio, mix them evenly, and obtain a mixture;

[0012] Step 2: calcining the mixture at 700° C.-750° C. and grinding to obtain a red luminescent material.

[0013] Preferably, in step 1, the sodium source is sodium carbonate.

[0014] Preferably, in step 1, the titanium source is titanium dioxide.

[0015] Preferably, in step 1, the europium source is europium oxide.

[0016] Preferably, in step 2, the calcination time is 6h-8h.

[0017] Preferably, in step 2, the temperature is raised to 700°C-750°C by programmed heating, and the heating rate is 4°C / min-6°C / min.

[0018] A third aspect of the present invention provides an LED lamp made using the red luminescent material.

[0019] A fourth aspect of the present invention provides application of the LED lamp in the field of plant growth.

[0020] In summary, the present invention provides a near-ultraviolet light-excited red luminescent material with a titanate matrix and europium ion doping, the red luminescent material having good luminescent intensity and stable luminescent performance, and an LED lamp prepared using the red luminescent material can meet the requirements of plant growth, and the preparation method is simple and the cost is low. The technical solution of the present invention can effectively solve the problems of high preparation cost, low luminescent intensity and unstable luminescent efficiency of the red light materials used in existing plant growth LED lamps. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 X-ray diffraction patterns of the red luminescent materials obtained in Examples 1-3 and Comparative Examples 1-2;

[0022] Figure 2 This is a SEM image of the red luminescent material obtained in Example 1;

[0023] Figure 3 This is a STEM image of the red luminescent material obtained in Example 1;

[0024] Figure 4 This is the Na element distribution diagram of the red light-emitting material obtained in Example 1;

[0025] Figure 5 This is the Ti element distribution diagram of the red luminescent material obtained in Example 1;

[0026] Figure 6 This is the O element distribution diagram of the red luminescent material obtained in Example 1;

[0027] Figure 7 This is the Eu element distribution diagram of the red luminescent material obtained in Example 1;

[0028] Figure 8 This is an energy dispersion X-ray diagram of the red luminescent material obtained in Example 1;

[0029] Fig. 9 This is the X-ray photoelectron spectrum of the red luminescent material obtained in Example 1;

[0030] Fig.10 This is a high-resolution spectrum of the Na element in the red luminescent material obtained in Example 1;

[0031] Fig.11 This is a high-resolution spectrum of the Ti element in the red luminescent material obtained in Example 1;

[0032] Fig.12 This is a high-resolution spectrum of the O element in the red luminescent material obtained in Example 1;

[0033] Fig.13 This is a high-resolution spectrum of the Eu element in the red luminescent material obtained in Example 1;

[0034] Fig.14 The excitation spectra of the red luminescent materials obtained in Examples 1-3 and Comparative Examples 1-2;

[0035] Fig.15 The emission spectra of the red luminescent materials obtained in Examples 1-3 and Comparative Examples 1-2;

[0036] Fig.16 This is the CIE coordinate diagram of the red luminescent material obtained in Example 1;

[0037] Fig.17 This is a performance test diagram of an LED device prepared using the red light-emitting material obtained in Example 1. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] Example 1

[0040] This embodiment provides a red luminescent material Na2TiO3:0.05Eu 3+ The preparation method specifically comprises the following steps:

[0041] Step 1: Weigh 0.1165 g of sodium carbonate, 0.0799 g of titanium dioxide and 0.0188 g of europium oxide, mix them, and grind them manually in an agate mortar for 1 h to obtain a mixture;

[0042] Step 2: Transfer the mixture into a crucible, place it in a muffle furnace, heat it to 750°C at a rate of 5°C / min, calcine it for 8 hours, cool it naturally, and obtain a block product. Grind it to obtain the red luminescent material Na2TiO3:0.05Eu 3+ .

[0043] Example 2

[0044] This embodiment provides a red luminescent material Na2TiO3:0.025Eu 3+ The preparation method specifically comprises the following steps:

[0045] Step 1: Weigh 0.1165 g of sodium carbonate, 0.0799 g of titanium dioxide and 0.009 g of europium oxide, mix them, and grind them manually in an agate mortar for 1 h to obtain a mixture;

[0046] Step 2: Transfer the mixture into a crucible, place it in a muffle furnace, heat it to 750°C at a rate of 5°C / min, calcine it for 8 hours, cool it naturally, and obtain a block product. Grind it to obtain the red luminescent material Na2TiO3:0.025Eu 3+ .

[0047] Example 3

[0048] This embodiment provides a red luminescent material Na2TiO3:0.0125Eu 3+ The preparation method specifically comprises the following steps:

[0049] Step 1: Weigh 0.1165 g of sodium carbonate, 0.0799 g of titanium dioxide and 0.0045 g of europium oxide, mix them, and grind them manually in an agate mortar for 1 h to obtain a mixture;

[0050] Step 2: Transfer the mixture into a crucible, place it in a muffle furnace, heat it to 750°C at a rate of 5°C / min, calcine it for 8 hours, cool it naturally, and obtain a block product. Grind it to obtain the red luminescent material Na2TiO3:0.0125Eu 3+ .

[0051] Comparative Example 1

[0052] This comparative example provides a red luminescent material Na2TiO3:0.1Eu 3+ The preparation method specifically comprises the following steps:

[0053] Step 1: Weigh 0.1165 g of sodium carbonate, 0.0799 g of titanium dioxide and 0.0369 g of europium oxide, mix them, and grind them manually in an agate mortar for 1 h to obtain a mixture;

[0054] Step 2: Transfer the mixture into a crucible, place it in a muffle furnace, heat it to 750°C at a rate of 5°C / min, calcine it for 8 hours, cool it naturally, and obtain a block product. Grind it to obtain the red luminescent material Na2TiO3:0.1Eu 3+ .

[0055] Comparative Example 2

[0056] This comparative example provides a red luminescent material Na2TiO3:0.2Eu 3+ The preparation method specifically comprises the following steps:

[0057] Step 1: Weigh 0.1165 g of sodium carbonate, 0.0799 g of titanium dioxide and 0.073 g of europium oxide, mix them, and grind them manually in an agate mortar for 1 h to obtain a mixture;

[0058] Step 2: Transfer the mixture into a crucible, place it in a muffle furnace, heat it to 750°C at a rate of 5°C / min, calcine it for 8 hours, cool it naturally, and obtain a block product. Grind it to obtain the red luminescent material Na2TiO3:0.05Eu 3+ .

[0059] In order to further demonstrate the technical effect of the present invention, the present invention performs XRD test on the red luminescent materials obtained in Examples 1-3 and Comparative Examples 1-2. The test results are as follows: Figure 1 As shown. Figure 1 It can be seen that the diffraction spectrum of the matrix (Na2TiO3) matches the spectrum of the standard card (PDF#50-0110). Na2TiO3 (PDF#50-0110) belongs to the trigonal system, R-3 (148) space group, and the lattice constants are a=b=13.92Å, c=7.67Å. θ The diffraction peaks at 12.70°, 22.64°, 34.45°, 35.03°, 40.15°, 57.67° and 58.51° correspond to the (110), (211), (321), (003), (232), (710) and (324) crystal planes, respectively. When the doping amount of europium ions is 0.0125, 0.025 and 0.05, the peak position of the diffraction spectrum is consistent with the peak position of the Na2TiO3 matrix, and no impurity phase appears, which proves that after Eu is doped into the matrix to replace the position of Ti, the crystal structure does not undergo significant distortion. Eu replaces Ti because their valence states are consistent, both +3. When the doping amount of europium ions is ≥0.1, a large number of impurity peaks appear in the sample in the range of 20° to 35°, proving that the synthesized sample has undergone a distortion compared to the matrix crystal structure, that is, too much Eu enters the crystal lattice and partially replaces Ti. The excess Eu is located in the lattice gaps or grain boundaries, and excessive Eu causes energy level overlap during electron transitions, which is not conducive to luminescence.

[0060] The present invention is to obtain the red luminescent material Na2TiO3:0.05Eu in Example 1 3+ Scanning electron microscopy tests were performed and the results were as follows Figure 2 As shown. Figure 2 It can be seen that Na2TiO3:0.05Eu 3+ It presents a submicron block structure with uniform size, and the length of each side is between 300nm-800nm. 3+ The internal microstructure of Figure 3-7 As shown, Figure 3 Na2TiO3:0.05Eu under high-angle annular dark field imaging 3+ Sample photos of Figure 4-7 Na2TiO3:0.05Eu 3+ Scanning transmission electron microscope element distribution map. Figure 3 It can be seen that the size of the two-dimensional structure presented by the three-dimensional structure after projection is consistent with that presented by SEM, which further proves that the synthesized sample is a submicron block structure. Figure 4-7 It can be seen that the elements Na, Ti, O and Eu contained in the sample are marked in blue, green, yellow and red, respectively, among which it is clearly visible that the Eu element is uniformly doped into the matrix in the form of an activator, proving that the synthesized sample is successful.

[0061] The present invention also studies the red luminescent material Na2TiO3:0.05Eu obtained in Example 1 3+ Energy dispersive X-ray spectroscopy was performed, and the results are as follows Figure 8 As shown. Figure 8 It can be seen that Na2TiO3:0.05Eu 3+ The Na, Ti, O and Eu elements all appear clearly in the spectrum, among which Na, Ti and O are the main elements and Eu is the doping element, and their atomic percentages and mass percentages are 22.78%, 34.61%, 42.37%, 0.24% and 18.09%, 57.23%, 23.41%, 1.26%, respectively. Among them, the Cu element comes from the sample using Cu mesh as the carrier.

[0062] The present invention also uses X-ray photoelectron spectroscopy (XPS) to analyze the red luminescent material Na2TiO3:0.05Eu obtained in Example 1. 3+ The surface element composition and chemical environment of Figure 9-13 As shown. Figure 9-13 It can be seen that Na2TiO3:0.05Eu 3+The characteristic peaks of Na 1s, Ti 2p, O 1s and Eu 3d in the sample confirm the composition of the elements in the material. We analyzed the O 1s region and successfully identified three key types of surface chemical bonds. Among them, the binding energy at 529.0eV corresponds to the Ti-O bond, 531.0eV reveals the existence of surface -OH, and the binding energy of 535.3eV is attributed to the Na KLL Auger peak. This discovery strongly proves the presence of sodium in the material. In the Ti 2p region observation, we found two groups of characteristic peaks. One group is located at 464.9eV, which represents the Ti 2p 1 / 2 Ti 3+ The other group is located at 457.5eV and 464.2eV, representing Ti 2p 3 / 2 and 2p 1 / 2 Ti 4+ These findings provide important evidence for our in-depth understanding of the chemical state of titanium in materials. In addition, in the Eu 3d data, we observed two obvious peaks at 1132.8eV and 1162.5eV, representing the Eu 3d 5 / 2 and 3D 3 / 2 Eu 3+ This discovery further confirms the presence of europium in the material. Finally, for the high-resolution spectrum of Na 1s, it mainly contains a peak at 1070.7eV, which corresponds to the chemical bond of Na-O, and once again confirms the composition of sodium in the material.

[0063] The present invention conducted fluorescence spectrum test on the red luminescent materials obtained in Examples 1-3 and Comparative Examples 1-2. The results are as follows: Figure 14-15 As shown, Fig.14 The excitation spectra of the red luminescent materials obtained in Examples 1-3 and Comparative Examples 1-2 under 611 nm wavelength monitoring; Fig.15 The emission spectra of the red luminescent materials obtained in Examples 1-3 and Comparative Examples 1-2 at an excitation wavelength of 395 nm. Fig.14 It can be seen that there is an obvious excitation peak in the range of 200 to 350 nm, corresponding to Eu 3+ -O 2- The charge transfer band is formed by the charge transfer process between 350nm and 500nm. 3+ of f - f Characteristic excitation transition, the main transition in the long-wave band is at 395nm 7 F0→ 5 L6 transition. It can be seen that with the increase of the doping amount of europium ions, the excitation spectrum generally shows a trend of first rising and then falling, and the optimal europium ion doping amount is 5%. Fig.15 It can be seen that the red light emission from 550nm to 750nm in the red light region comes from Eu 3+ The strongest emission peak is at 614nm, coming from 5 D0→ 7 F2 transition. In addition, the second strongest peak at 703nm in the long-wave band comes from 5 D0→ 7 F4, this band is the specific wavelength absorption band of chlorophyll synthesis in plant growth, which is of great significance to plant growth. Consistent with the excitation spectrum, with the increase of the doping amount of europium ions, its emission spectrum generally shows a trend of first rising and then falling. The optimal europium ion doping amount is 5%. Concentration quenching will occur when the doping amount is greater than this value.

[0064] The present invention is to obtain the red luminescent material Na2TiO3:0.05Eu in Example 1 3+ CIE test was carried out and the results are as follows Fig.16 As shown, according to Fig.16 It can be seen that the red luminescent material Na2TiO3:0.05Eu obtained in Example 1 3+ The CIE value of is (0.649, 0.351), which is very close to the NTSC standard red value (0.670, 0.330), proving that the red luminescent material Na2TiO3:0.05Eu obtained in Example 1 3+ It has typical red light emission characteristics.

[0065] The present invention uses the red luminescent material Na2TiO3:0.05Eu obtained in Example 1 3+ After the powder was mixed with epoxy resin, it was packaged on an InGaN chip to make an LED lamp, and the performance of the LED lamp was tested. The results are as follows Fig.17 As shown. Fig.17 It can be seen that when the driving current increases from 10mA to 60mA, the overall emission intensity gradually increases without overexposure, proving that Na2TiO3:0.05Eu 3+ The powder can be effectively excited by 395nm blue light and can be used as red light material for plant growth LED lights.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A red luminescent material, characterized in that: Its general chemical formula is Na2TiO3:xEu 3+ , 0.0125≤x≤0.

05.

2. The red luminescent material according to claim 1, characterized in that: The red light-emitting material is a trigonal crystal system and has an R-3 (148) space group structure.

3. The method for preparing a red luminescent material according to claim 1 or 2, characterized in that: The steps include: Step 1: weigh a sodium source, a titanium source and a europium source according to the designed ratio, mix them evenly, and obtain a mixture; Step 2: calcining the mixture at 700° C.-750° C. and grinding to obtain a red luminescent material.

4. The method for preparing a red luminescent material according to claim 3, characterized in that: In step 1, the sodium source is sodium carbonate.

5. The method for preparing a red luminescent material according to claim 3, characterized in that: In step 1, the titanium source is titanium dioxide.

6. The method for preparing a red luminescent material according to claim 3, characterized in that: In step 1, the europium source is europium oxide.

7. The method for preparing a red luminescent material according to claim 3, characterized in that: In step 2, the calcination time is 6h-8h.

8. The method for preparing a red luminescent material according to claim 3, characterized in that: In step 2, the temperature is raised to 700°C-750°C by programmed heating, with a heating rate of 4°C / min-6°C / min.

9. An LED lamp, characterized in that: It is prepared using the red luminescent material described in claim 1 or 2.

10. Application of the LED lamp as claimed in claim 9 in the field of plant growth.

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