Single Eu-doped perovskite fluorescent powder as well as preparation method and application thereof

Abstract

The invention discloses single Eu-doped perovskite fluorescent powder and a preparation method and application thereof, and belongs to the technical field of luminescent materials, the molecular formula is NaYSrWO6: xEu < 3 + >, and x is equal to 0.005-0.5. The preparation method comprises the following steps: weighing the raw materials according to the stoichiometric ratio, mixing and grinding, heating and preheating the obtained powder, quickly heating and calcining, and crushing and grinding after calcining to obtain the Eu-singly-doped perovskite fluorescent powder. The double-perovskite tungstate NaYSrWO6: xEu < 3 + > fluorescent powder provided by the invention can have both high-efficiency photoluminescence (PL) and thermoluminescence (TL) performances, and has application potential in the aspects of white light LED, real-time low-dose-rate accurate measurement and X-ray imaging.

Description

Technical Field

[0001] The present invention belongs to the technical field of luminescent materials, and in particular relates to a single-Eu-doped perovskite phosphor and a preparation method and application thereof. Background Art

[0002] The name Perovskite comes from the famous Russian geologist Lev Perovski. It refers to a class of compounds represented by ABO3 type oxides. ABO3 type perovskite materials have excellent optical and electrical properties due to their unique lattice structure, making them a research hotspot in the field of materials science. Perovskite materials can be located at the A position or the B position (i.e., A 1-x A' x BO3 or AB 1-x B' x O3) can flexibly accommodate a variety of cations. When cations of appropriate size are incorporated into the A or B site, these doped cations can form either a disordered or ordered structure with the existing cations. If a disordered structure is formed, the basic structure of the perovskite is preserved; if an ordered structure is formed, it is called a double perovskite. The chemical formulas of double perovskites include A2BB'O6, AA'B2O6, or AA'BB'O6. Double perovskites are more diverse in elemental composition and crystal structure than traditional perovskites, and their physical properties are particularly outstanding.

[0003] Among phosphor matrices such as phosphate, silicate, tungstate, aluminate, nitride, and fluoride, tungstate matrix has become the focus of functional material research due to its excellent physicochemical stability, low cost, and simple synthesis process. Tungstate system phosphors cover two main structures: W 6+ With four O 2- The formed [WO4] tetrahedral structure (scheelite structure) and W 6+ With six O 2- The [WO6] octahedral double perovskite structure is formed. Tungstate phosphors are characterized by their unique physical and chemical properties and (WO4) 2- and (WO6) 6- The self-luminescent ligand properties of the double perovskite tungstate NaLaMgWO6:Sm 3+ Red phosphor can be used as a potential application material for LED; AlsabahYA et al. synthesized double perovskite tungstate Ba2Zn 1-x Ni x WO6 (0≤x≤1) series, this series of samples shows potential application value in photovoltaic energy conversion; HuW et al. synthesized Er 3+ Doping and Er3+ / Ho 3+ Co-doped LiYMgWO6 phosphor is used in the anti-counterfeiting field.

[0004] White LED lamps are gradually replacing traditional lighting equipment due to their significant advantages such as high luminous efficiency, low energy consumption and environmental protection. At present, the commercial white LEDs widely used in the market are mainly composed of blue light-emitting diode chips based on gallium nitride (GaN) and yellow phosphors (YAG:Ce 3+ ) composition. However, this type of white light LED lacks red spectral components, resulting in a correlated color temperature of more than 7000K and a color rendering index of less than 80. These factors limit its application range to a certain extent. Another way to achieve white light LED is to form white light by combining red, green and blue LED chips, but this method has problems such as complex structural design, high material and process costs, and high-precision control requirements, resulting in a comprehensive cost far exceeding that of phosphor-converted white light LEDs. Another solution is to use ultraviolet / near-ultraviolet chips to excite red, green and blue phosphors to produce white light, but this method has problems with reabsorption and inaccurate ratio control. Therefore, it is particularly important to develop corresponding red phosphors. At present, commercial red phosphors such as CaAl SiN3:Eu 2+ 、Y2O2S:Eu 3+ and Y2O3:Eu 3+ In order to achieve indoor lighting effects that better meet the visual needs of the human eye and expand the application range of LEDs, it is crucial to develop a new type of red phosphor with simple preparation process, low cost and excellent performance.

[0005] Eu 3+ It can be used as a luminescent center for LED lighting applications. Its emission band is located in the orange-red part of visible light, which is caused by the magnetic dipole transition 5D0→7F1 or the electric dipole transition 5D0→7F2. 3+ The charge transfer is an effective method to improve the luminous intensity and efficiency of fluorescent materials. The octahedral double perovskite tungstate system has unique photophysical properties. Under ultraviolet radiation, the material will undergo significant electronic transitions. 2- The 2P6 orbital electrons are excited to the W of the adjacent tungsten center. 6+ The 5d0 orbital of the material's crystal structure significantly improves the charge transfer efficiency of the WO6 group under strong ultraviolet or near-ultraviolet light conditions. This unique energy transfer mechanism allows the lattice to directly transfer absorbed light energy to the doped rare earth ion, thereby multiplying the luminous intensity of the fluorescent material and providing strong support for its application in the LED field.

[0006] Compared with other dose measurement technologies, thermoluminescence exhibits excellent sensitivity and a wide dynamic range. As a key medium for dose measurement, thermoluminescent materials have a highly sensitive response to ionizing radiation, can detect extremely low dose rates, and have a wide linear range, which is suitable for real-time monitoring from background radiation to high dose rate environments. In addition, thermoluminescent materials are also resistant to high temperatures and electromagnetic interference, and can maintain stable performance in complex environments. Coupled with their low cost, long service life and reusability, thermoluminescent materials play a vital role in radiation monitoring and other fields. The development of high-performance thermoluminescent dosimeter materials has important theoretical significance and practical application value for achieving more efficient radiation dose monitoring and improving the accuracy and stability of radiation dose measurement. Double perovskite tungstate exhibits the advantages of high photoluminescence efficiency, wide emission spectrum and high stability. These characteristics make it suitable not only for the LED field, but also for the field of radiation dose measurement. For example, Ca3WO6:Ho 3+ 、Ca3WO6:Tb 3+ and Ca3WO6:Er 3+ Double perovskite tungstates, such as tungstates, have shown promising application prospects in LED lighting and radiation dosimetry. The unique energy transfer mechanism of tungstate groups can significantly enhance X-ray luminescence, a property that helps achieve higher sensitivity and deep optical imaging, and is expected to be applied in the field of X-ray imaging. Summary of the Invention

[0007] In order to solve the above technical problems, the present invention proposes a single-doped Eu perovskite phosphor and its preparation method and application.

[0008] To achieve the above objectives, the present invention provides the following technical solutions:

[0009] A single Eu-doped perovskite phosphor with the molecular formula NaYSrWO6:xEu 3+ , wherein x represents the Eu doping amount; x = 0.005-0.5, preferably, x = 0.005, 0.01, 0.05, 0.1, 0.15, 0.2, 0.3 or 0.5.

[0010] Beneficial effect: The present invention dopes Eu into the new double perovskite tungstate matrix. 3+ , and realize the application in white light LED, real-time dose rate detection and X-ray imaging. In the present invention, the double perovskite tungstate NaYSrWO6:xEu is synthesized by high temperature solid phase method. 3+(x=0.005, 0.01, 0.05, 0.1, 0.15, 0.2, 0.3, 0.5) phosphors, which can be excited by commercial blue light chips and then used in LED lighting. The samples have strong orange-red emission under 325nm excitation. Eu 3+ The increase in doping concentration has little effect on the luminescent chromaticity of the phosphor. The color temperature of the material at different concentrations is below 2000K, which can meet the needs of indoor lighting LEDs, and the phosphor provided by the present invention has good thermal stability and good luminous efficiency. The increase in temperature has little effect on color purity and color temperature, and has potential application value in the field of lighting. The phosphor provided by the present invention shows high sensitivity and rapid response to X-rays at low doses, and can be used for real-time dose rate measurement. It has fast response and short attenuation at different dose rates, and can also be used in X-ray imaging. In summary, the double perovskite tungstate NaYSrWO6:xEu provided by the present invention 3+ It can achieve photoluminescence and radiation response simultaneously and simultaneously, and has application potential in white light LEDs, real-time dose rate detection and X-ray imaging.

[0011] A method for preparing a single Eu-doped perovskite phosphor comprises the following steps:

[0012] The raw materials are weighed according to the stoichiometric ratio, mixed and ground, and the obtained powder is preheated and then rapidly heated and calcined. After the calcination, the powder is crushed and ground to obtain the single-doped Eu perovskite phosphor.

[0013] Preferably, the raw materials include tungsten trioxide, yttrium oxide, strontium salt, sodium salt and europium oxide.

[0014] Preferably, the strontium salt is strontium carbonate.

[0015] Preferably, the sodium salt is sodium carbonate.

[0016] Preferably, the preheating temperature is 900° C. and the preheating time is 1 hour.

[0017] Preferably, the calcination temperature is 1200° C. and the calcination time is 8 hours.

[0018] Application of a single Eu-doped perovskite phosphor in X-ray imaging.

[0019] Application of a single Eu-doped perovskite phosphor in LED lighting.

[0020] Application of a single Eu-doped perovskite phosphor in radiation dose measurement.

[0021] Compared with the prior art, the present invention has the following advantages and technical effects:

[0022] The present invention is based on the inspiration of excellent double perovskite tungstate materials NaLaMgWO6, NaGdMgWO6 and NaYMgWO6, and provides a comprehensive luminescence property of a trivalent europium ion activated tungstate double perovskite phosphor NaYSrWO6. The double perovskite tungstate NaYSrWO6 provided by the present invention: xEu 3+ Phosphors can combine efficient photoluminescence (PL) and thermoluminescence (TL) properties, and have application potential in white light LEDs, real-time low-dose rate precision measurement, and X-ray imaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of this application. The exemplary embodiments and descriptions of this application are intended to explain this application and do not constitute an improper limitation on this application. In the accompanying drawings:

[0024] Figure 1 NaYSrWO6:0.15Eu obtained in Example 1 3+ SEM images of

[0025] Figure 2 NaYSrWO6:xEu obtained in Example 1 3+ The excitation spectrum of phosphor (λ ex =605nm);

[0026] Figure 3 NaYSrWO6:xEu obtained in Example 1-8 3+ Emission spectrum of phosphor (λ ex =325nm);

[0027] Figure 4 NaYSrWO6:xEu obtained in Example 1-8 3+ Chromaticity diagram of phosphor (=325nm);

[0028] Figure 5 NaYSrWO6:0.15Eu obtained in Example 1 3+ Schematic diagram of the relationship between the temperature-dependent fluorescence spectrum of the phosphor (a) and the luminous intensity and temperature (λ ex =325mn)(b);

[0029] Figure 6 In formula 5 and Schematic diagram of the linear relationship;

[0030] Figure 7 NaYSrWO6:0.15Eu obtained in Example 1 3+ Quantum efficiency of phosphors;

[0031] Figure 8NaYSrWO6:xEu obtained in Example 1-8 3+ Thermoluminescence curve of phosphor;

[0032] Figure 9 NaYSrWO6:0.3Eu obtained in Example 7 3+ TL luminescence curve of phosphor;

[0033] Figure 10 NaYSrWO6:xEu obtained in Example 2-8 3+ Low-temperature two-dimensional thermoluminescence spectra (100-550K) of the phosphors (x = 0.005, 0.01, 0.05, 0.1, 0.2, 0.3, 0.5) after 3 mins of X-ray excitation (approximately 18.6 mGy);

[0034] Figure 11 NaYSrWO6:xEu obtained in Examples 3 and 5-8 3+ Three-dimensional thermoluminescence spectra of the phosphors (x = 0.01, 0.1, 0.2, 0.3, 0.5) after 3 mins of X-ray excitation (approximately 18.6 mGy);

[0035] Figure 12 NaYSrWO6:xEu obtained in Example 2-8 3+ Low-temperature three-dimensional thermoluminescence spectra (100-550K) of the phosphors (x = 0.005, 0.01, 0.05, 0.1, 0.15, 0.2, 0.3) after 3 minutes of X-ray excitation (approximately 18.6 mGy);

[0036] Figure 13 The NaYSrWO6:xEu obtained in Example 2-8 was analyzed based on the initial rise method. 3+ (x=0.005, 0.01, 0.05, 0.1, 0.15, 0.2, 0.3) phosphor trap depth map;

[0037] Figure 14 (a) is the NaYSrWO6:0.3Eu obtained in Example 7 3+ Luminescence spectra of phosphors under different X-ray dose rates, (b) is NaYSrWO6:0.3Eu obtained in Example 7 3+ Schematic diagram of the linear relationship between the RL intensity and the dose rate of the phosphor. (c) is the NaYSrWO6:0.3Eu obtained in Example 7. 3+ RL curves of phosphor at different dose rates;

[0038] Figure 15 NaYSrWO6:0.3Eu obtained in Example 7 3+ Repeatability study of phosphors. DETAILED DESCRIPTION

[0039] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0040] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0041] Unless otherwise specified, the raw materials in the examples of the present invention were purchased from commercial sources;

[0042] Among them, tungsten trioxide (WO3, purity 99.8%), yttrium oxide (Y2O3, purity 99.9%), strontium carbonate (SrCO3, purity 99.9%), sodium carbonate (Na2CO3, purity 99.9%), and europium oxide (Eu2O3, purity 99.9%) were all purchased from Shanghai Aladdin Co., Ltd.

[0043] Unless otherwise specified, room temperature or normal temperature in the embodiments of the present invention refers to 25±3°C.

[0044] Example 1

[0045] A high-temperature solid-phase method for preparing single-doped Eu 3+ The method of preparing NaYSrWO6 phosphor comprises the following steps:

[0046] Tungsten trioxide (WO3, 99.8%), yttrium oxide (Y2O3, 99.9%), strontium carbonate (SrCO3, 99.9%), sodium carbonate (Na2CO3, 99.9%), and europium oxide (Eu2O3, 99.9%) were placed on an electronic balance in a stoichiometric ratio (molar ratio, the same below) of 2:1:2:1:0.15 for precise weighing. The weighed raw materials were then poured into an agate mortar and fully ground for 20 minutes until the powder reached a uniform state. The obtained powdered raw materials were then sequentially loaded into a corundum crucible and placed in a muffle furnace for high-temperature heating treatment. The temperature was raised to 900°C in an air atmosphere for pre-calcination for 1 hour, and then raised to 1200°C for calcination for 8 hours to obtain a block-shaped sintered sample. After the sample cooled, it was fully ground using an agate mortar to obtain NaYSrWO6:0.15Eu 3+ Phosphor.

[0047] Example 2

[0048] A high-temperature solid-phase method for preparing single-doped Eu3+ The method for producing NaYSrWO6 phosphor powder is different from that of Example 1 only in that tungsten trioxide, yttrium oxide, strontium carbonate, sodium carbonate, and europium oxide are placed on an electronic balance in a stoichiometric ratio of 2:1:2:1:0.005 and accurately weighed. The remaining process steps and parameters are the same as those of Example 1, and finally NaYSrWO6:0.005Eu is obtained. 3+ Phosphor.

[0049] Example 3

[0050] A high-temperature solid-phase method for preparing single-doped Eu 3+ The method for producing NaYSrWO6 phosphor powder is different from that of Example 1 only in that tungsten trioxide, yttrium oxide, strontium carbonate, sodium carbonate, and europium oxide are placed on an electronic balance in a stoichiometric ratio of 2:1:2:1:0.01 and accurately weighed. The remaining process steps and parameters are the same as those of Example 1, and finally NaYSrWO6:0.01Eu 3+ Phosphor.

[0051] Example 4

[0052] A high-temperature solid-phase method for preparing single-doped Eu 3+ The method for producing NaYSrWO6 phosphor powder is different from that of Example 1 only in that tungsten trioxide, yttrium oxide, strontium carbonate, sodium carbonate, and europium oxide are placed on an electronic balance in a stoichiometric ratio of 2:1:2:1:0.05 and accurately weighed. The remaining process steps and parameters are the same as those of Example 1, and finally NaYSrWO6:0.05Eu is obtained. 3+ Phosphor.

[0053] Example 5

[0054] A high-temperature solid-phase method for preparing single-doped Eu 3+ The method for producing NaYSrWO6 phosphor powder is different from that of Example 1 only in that tungsten trioxide, yttrium oxide, strontium carbonate, sodium carbonate, and europium oxide are placed on an electronic balance in a stoichiometric ratio of 2:1:2:1:0.2 and accurately weighed. The remaining process steps and parameters are the same as those of Example 1, and finally NaYSrWO6:0.1Eu 3+ Phosphor.

[0055] Example 6

[0056] A high-temperature solid-phase method for preparing single-doped Eu 3+The method for producing NaYSrWO6 phosphor powder is different from that of Example 1 only in that tungsten trioxide, yttrium oxide, strontium carbonate, sodium carbonate, and europium oxide are placed on an electronic balance in a stoichiometric ratio of 2:1:2:1:0.2 and accurately weighed. The remaining process steps and parameters are the same as those of Example 1, and finally NaYSrWO6:0.2Eu is obtained. 3+ Phosphor.

[0057] Example 7

[0058] A high-temperature solid-phase method for preparing single-doped Eu 3+ The method for producing NaYSrWO6 phosphor powder is different from that of Example 1 only in that tungsten trioxide, yttrium oxide, strontium carbonate, sodium carbonate, and europium oxide are placed on an electronic balance in a stoichiometric ratio of 2:1:2:1:0.3 and accurately weighed. The remaining process steps and parameters are the same as those of Example 1, and finally NaYSrWO6:0.3Eu 3+ Phosphor.

[0059] Example 8

[0060] A high-temperature solid-phase method for preparing single-doped Eu 3+ The method for producing NaYSrWO6 phosphor powder is different from that of Example 1 only in that tungsten trioxide, yttrium oxide, strontium carbonate, sodium carbonate, and europium oxide are placed on an electronic balance in a stoichiometric ratio of 2:1:2:1:0.5 and accurately weighed. The remaining process steps and parameters are the same as those of Example 1, and finally NaYSrWO6:0.5Eu 3+ Phosphor.

[0061] Technical effects:

[0062] 1. Detection equipment and methods

[0063] (1) Fluorescence spectrum test was performed using Shanghai Lingguang F-98 fluorescence spectrometer with a spectral resolution of 0.2 nm, a Xe lamp as the excitation light source, a PMT gain voltage of 550 V, an excitation wavelength detection range of 200 nm to 600 nm, an emission wavelength detection range of 400 nm to 800 nm, an excitation bandwidth of 5 nm and an emission bandwidth of 5 nm, and a wavelength interval of 1 nm.

[0064] (2) The SEM of the samples was measured using a scanning electron microscope (TESCAN MIRA LMS, Czech Republic). The samples were dispersed in ethanol, the ultrasonic time was 10 min, and the test mode was secondary electron.

[0065] (3) A steady-state / transient fluorescence spectrometer (FLS1000, Edinburgh, UK) was used to analyze the temperature-dependent fluorescence spectra and quantum efficiency of the samples. The temperature-dependent fluorescence spectra were tested at 298K, 323K, 373K, 423K, and 473K, with an excitation wavelength of 325nm and a scanning range of 400nm-800nm. The quantum yield was tested at an excitation wavelength of 325nm and a scanning range of 400nm-800nm.

[0066] (4) The samples were irradiated and XEL was measured using an LTTL3DS thermoelectroluminescence spectrometer (Guangzhou Redi Aison Technology Co., Ltd.). The irradiation source was an X-ray tube with an operating voltage of 50 kV, a current of 10-80 μA (adjustable), and a dose rate of approximately 0.1 Gy·s. -1 The measurable spectral range is 300nm~1000nm, the spectral resolution is 1nm, and the sample ambient temperature can be set between 100K~773K.

[0067] 2. Test results

[0068] SEM analysis

[0069] The NaYSrWO6:0.15Eu obtained in Example 1 3+ The surface morphology of the phosphor samples was measured by SEM. Figure 1 As shown, it can be seen that the phosphor obtained in Example 1 is in an irregular shape of 1 to 2 μm, has a regular appearance, a smooth surface, good dispersibility, and a relatively uniform morphology.

[0070] 2.2 Excitation spectrum analysis

[0071] NaYSrWO6:xEu obtained in Example 1-8 3+ The excitation spectra of the phosphors are similar. The excitation spectra of the phosphors obtained in Example 1 are tested. The results are as follows: Figure 2 As shown, at a detection wavelength of 605 nm, the absorption spectrum of the phosphor shows a widely distributed absorption band, consisting of a broadband and multiple Eu 3+ The characteristic excitation bands of O 2- →W 6+ and O 2- →Eu 3+ Between 350nm and 600nm, some sharp excitation peaks can be observed, which can be attributed to Eu 3+ of 7 F0→ 5 D4 (363nm), 7 F0→ 5 L7 (381nm),7 F0→ 5 L6 (394nm), 7 F0→ 5 D3 (413nm), 7 F0→ 5 D2 (464nm), 7 F0→ 5 D1 (530nm) and 7 F0→ 5 The characteristic transition of D0 (583nm). Figure 2 As shown, NaYSrWO6:xEu 3+ The phosphor has strong excitation at 394nm, indicating that the sample can be well excited by commercial blue light chips and has great application potential in LED lighting applications.

[0072] 2.3 Emission spectrum analysis

[0073] The peak of the absorption peak of 325nm was used as the optimal excitation wavelength of the sample to scan the emission spectrum, and it was found that the NaYSrWO6:xEu obtained in Examples 1-8 3+ (x=0.005, 0.01, 0.05, 0.1, 0.15, 0.2, 0.3, 0.5) phosphor samples all have strong orange-red emission under 325nm excitation, with a peak at 588nm corresponding to the magnetic dipole transition. 5 D0→ 7 F1, with a peak at 578nm, 605nm, 660nm and 715nm, corresponding to electric dipole transitions 5 D0→ 7 F J (J=0,2,3,4), these are all Eu 3+ The series of 4f→4f characteristic emissions. According to the selection rules, if a site has inversion symmetry, the electric dipole transition is prohibited, in which case the magnetic dipole transition at 588nm will dominate. If the site lacks inversion symmetry, the electric dipole transition is allowed. The strongest emission peak at 605nm comes from 5 D0→ 7 F2 transition, so Eu 3+ The ions occupy a non-inversion symmetric lattice, a property that is beneficial for red phosphors.

[0074] like Figure 3 As shown, with the doping of Eu 3+ When the concentration is from x=0.005 to x=0.15, the emission intensity of the phosphor increases with the 3+ The luminescence intensity increases with the increase of Eu ion concentration, and finally reaches the highest when the doping concentration x = 0.15. 3+With the further increase of ion concentration, the luminescence intensity gradually weakened, and eventually the luminescence intensity quenching phenomenon occurred.

[0075] 2.4 Color Coordinate Analysis

[0076] like Figure 4 As shown, under the excitation of 325nm, the phosphor NaYSrWO6:xEu obtained in Examples 1-8 3+ The CIE coordinates of (x=0.005,0.01,0.05,0.1,0.15,0.2,0.3,0.5) are as Eu 3+ As the concentration increases, the color coordinates from sequence 1 to sequence 3 move to the upper right orange-red area. The color coordinates from sequence 4 to sequence 7 have almost no change. Starting from sequence 8, due to concentration quenching, they move to the lower left corner. The standard deviation of the color coordinates is calculated using formula 1 and formula 2. Where Δx and Δy are standard deviations, x n and y n For different Eu 3+ The chromaticity coordinates under concentration, x and y are the average values ​​of the chromaticity coordinates.

[0077]

[0078] Among them, NaYSrWO6:xEu 3+ The average value of the chromaticity coordinates of (x=0.005, 0.01, 0.05, 0.1, 0.15, 0.2, 0.3, 0.5) is x=0.56799875, y=0.342895, Δx is 0.00241643, Δy is 0.00035250. 3+ The average value of the chromaticity coordinates of (x=0.1,0.15,0.2,0.3) is x=0.6036275,y=0.355905,Δx is 0.00000495,Δy is 0.00000161. The results show that NaYSrWO6:xEu 3+ In the range of (x=0.1,0.15,0.2,0.3), Eu 3+ The increase in doping concentration has little effect on the luminescence chromaticity of the phosphor.

[0079] To further analyze the phosphor's luminescence performance, the sample's color purity and color temperature were calculated using Equations 3 and 4. Color temperature (CCT) represents the temperature of a color. Specifically, when a standard black body is heated to a certain temperature, the color of the light it emits matches the color of light emitted by a specific light source. The heating temperature of the black body is the color temperature of that light source. Color purity refers to the percentage of the original color in the overall color, and is often used to describe the intensity of a color.

[0080]

[0081] In formula 3, (x, y), (x i ,y i ) and (x d ,y d ) represent the chromaticity coordinates of phosphor, standard white light and main wavelength emission respectively. d ,y d ) is the color coordinate corresponding to the main wavelength. The chromaticity coordinates of standard white light are (0.333, 0.333), and the chromaticity coordinates of the main wavelength 605mn emission are (0.64823, 0.35139).

[0082] CCT=-437n 3 +3601n 2 -6861n+5514.31 (4)

[0083] In formula 4 (x, y) are the sample's color coordinates. The calculated color coordinates and color temperature of the phosphor are shown in Table 1. The results show that the color purity at the optimal doping concentration is around 87%, demonstrating the sample's high color purity. Excessively high color temperatures are harmful to the human eye, while temperatures below 3000K are considered warm and suitable for white LEDs. The color temperature of this material at various concentrations remains below 2000K. This indicates that this red phosphor can meet the requirements of indoor white LED lighting and has potential application value in the LED lighting field.

[0084] Table 1 NaYSrWO6:xEu 3+ (x = 0.005, 0.01, 0.05, 0.1, 0.15, 0.2, 0.3, 0.5) CIE color coordinates, color purity and color temperature

[0085]

[0086]

[0087] 2.5 Temperature-dependent fluorescence spectroscopy and thermal stability analysis

[0088] The thermal quenching characteristics of phosphors have an important impact on their application in indoor lighting LEDs. Figure 5 (a) shows the NaYSrWO6:0.15E obtained in Example 1 3+ The fluorescence spectrum of phosphor from 298K to 473K (λ ex =325mn). It can be seen that the emission spectrum originates from Eu 3+ The characteristic transitions of the ions form specific emission peaks. Temperature changes have no effect on the position and shape of the emission spectrum, indicating that the sample's crystal structure has good connectivity and strong overall rigidity, and has good photothermal stability during temperature changes.

[0089] However, temperature changes affect the luminescence intensity of the phosphor. Due to the thermal quenching effect, the luminescence intensity will gradually weaken as the temperature rises. Figure 5 Part (b) is the normalized NaYSrWO6:0.15Eu obtained in Example 1 3+ The relationship between the luminous intensity of the phosphor and temperature is shown in the graph. It shows that at temperatures of 373K and 423K, the luminous intensity remains at 77.87% and 62.69% of that at room temperature (298K). This indicates that the phosphor has good thermal stability.

[0090] In addition to the methods mentioned above, the modified Arrhenius equation can also be used to conduct a comprehensive and in-depth evaluation of its thermal quenching performance.

[0091]

[0092] Where I0 represents the luminescence intensity at room temperature, I represents the fluorescence intensity at a specified temperature T, ΔE and A represent the activation energy and thermal quenching constant, respectively, and K B is the Boltzmann constant (8.62×10 -5 eV / K), T is the temperature in Kelvin.

[0093] pass and The slope of the fitted straight line can be used to calculate the thermal quenching activation energy ΔE, as shown in the following example: Figure 6 As shown by Figure 6 It can be seen that there is a good linear relationship between the two (R 2 =0.99686), which indicates that the temperature quenching process of this material is consistent with the Arrhenius model. Its slope is -ΔE, so the activation energy ΔE is 0.214eV. Compared with other white light LED phosphor research results, such as CaSc2O4: 0.01Eu 2+ The activation energy of the phosphor is 0.1727eV, Li3Ba2Y3(WO4)8:4%Bi 3+ ,4%Eu 3+ The activation energy of the phosphor is 0.1897eV, NaYMgWO6:0.01Tm 3+ ,0.1Dy 3+ The activation energy of the phosphor is 0.25eV. 3+ The phosphor has good thermal stability.

[0094] Among them, the above phosphors are sourced from:

[0095] CaSc2O4:0.01Eu 2+Phosphor: Li Xiaojie.Eu 2+ Performance research and multifunctional application of activated oxide-based red phosphors[D]. Hebei University, 2024.

[0096] Li3Ba2Y3(WO4)8:4%Bi 3+ ,4%Eu 3+ Phosphor: Gu Junqiang. Preparation, performance regulation and application of tungstate luminescent materials in white light LEDs [D]. Jiangxi Normal University.

[0097] NaYSrWO6:0.15Eu 3+ Phosphor: Liu X, Cheng K, Shi Y, et al. An investigationabout the ability to change color and the way energy is transferred ofNaYMgWO6:RE 3+ (RE 3+ =Tm 3+ ,Dy 3+ ,Tm 3+ / Dy 3+ ): a new type of single-phase whitephosphor for WLEDs[J]. Materials ResearchBulletin, 2024,169:112539.

[0098] To further analyze the color stability of the phosphor during heating, the color purity and color temperature at different temperatures were analyzed, and the chromaticity shift of the color coordinates at different temperatures was calculated. The chromaticity shift (ΔE) can be calculated using the following formula.

[0099]

[0100] In formula 6,

[0101]

[0102] w′0=1-u′0-v′0;

[0103] w′ t =1-u′ t -v′ t .

[0104] Among them, (x0, y0) is the color coordinate at room temperature, (x t ,y t ) is the color coordinate at a given temperature.

[0105] According to the above formula, the phosphor NaYSrWO6:0.15Eu 3+ The color coordinates, color purity, color temperature and chromaticity shift at different temperatures are shown in Table 2, which shows that the increase in temperature has little effect on color purity and color temperature. Moreover, at the LED operating temperature (373K-423K), the chromaticity shift is only 0.006 and 0.012. 3+ The phosphor samples have good color stability.

[0106] Table 2NaYSrWO6:0.15Eu 3+ Color coordinates, color purity, color temperature and chromaticity shift at different temperatures

[0107]

[0108] Commercial red phosphor Y2O3:Eu 3+ The color coordinates are (0.6347, 0.3629), and the NaYSrWO6:0.15Eu obtained in Example 1 of the present invention 3+ The chromaticity shift of the phosphor is 0.027 at 298K, and the chromaticity shift is 0.033 and 0.039 at the LED operating temperature (373K-423K), indicating that the color luminescence performance of the sample is close to that of commercial red phosphor, which to a certain extent reflects its applicability in relevant application scenarios.

[0109] 2.6 Quantum Efficiency Analysis

[0110] The quantum efficiency of a phosphor can be used to analyze its luminous efficiency. The internal quantum efficiency (IQE) refers to the efficiency with which a phosphor converts absorbed energy into luminescent electrons. The external quantum efficiency (EQE) refers to the efficiency with which a phosphor converts absorbed light energy into luminescent photons that escape from the phosphor. The internal quantum efficiency (IQE) and external quantum efficiency (EQE) of a phosphor can be calculated using the following formulas.

[0111]

[0112] η EQE =η IQE ×η AE (9)

[0113] ∫L in Equations 7 and 8 S is the integrated area of ​​the sample’s emission spectrum, ∫E R is the integral area of ​​the excitation spectrum of the blank sample, ∫E S is the integral area of ​​the sample’s excitation spectrum, η AE is the absorption efficiency of the sample. Figure 7As shown, under the excitation of 325nm wavelength, the NaYSrWO6:0.15Eu obtained in Example 1 3+ The internal quantum efficiency of the phosphor is 64.4%, and the absorption efficiency is 78.65%. The external quantum efficiency calculated according to formula 9 is 50.65%, which proves that the sample has good luminous efficiency.

[0114] 2.7 Two-dimensional thermoluminescence spectroscopy

[0115] The thermoluminescence curves of the phosphors obtained in Examples 1-8 were measured using an X-ray tube irradiation of 20 mGy (heating rate of 5 K / s). The measurement results are as follows: Figure 8 As shown, it can be seen that with the 3+ As the doping concentration increases, the thermoluminescence intensity gradually increases. 3+ When the doping concentration is x=0.3 (ie Example 7), the thermoluminescence intensity is the strongest. 3+ , there is a clear concentration quenching phenomenon, the thermoluminescence intensity decreases. The optimal doping ratio of the thermoluminescence curve is determined to be x = 0.3. Subsequently, different methods are used to analyze the thermoluminescence curve of the sample with the confirmed optimal doping concentration, and the optimal sample NaYSrWO6:0.3u is tested. 3+ The X-ray excitation spectrum of the sample shows that the phosphor can be effectively excited by X-rays to emit light, which can be detected by radiation dose.

[0116] The TL luminescence peak temperature determines whether the material is suitable for radiation dose measurement. The luminescence peak above 200℃ has good stability and the signal is not easy to decay over time, which can be used for radiation dose measurement. Here, the TL general kinetic equation can be used to fit the optimal sample NaYSrWO6:0.3u 3+ Luminous curve.

[0117]

[0118] In formula (10), T is the absolute temperature, n0 is the concentration of trapped electrons at the initial temperature T0, E is the trap depth, and S = S'n0 n-1 is the frequency factor, b is the kinetic series, k is the Boltzmann constant, and the heating rate β = dT / dt.

[0119] like Figure 9 As shown, NaYSrWO6:0.3u 3+ The fitting results of thermoluminescence curves show that there are four TL luminescence peaks, of which there are two main TL luminescence peaks. The luminescence intensity of the peak at 405K is the largest, corresponding to Peak1, followed by the peak at 460K, corresponding to Peak4. The peak at 405K has a higher sensitivity, so it has better thermal stability. 3+The luminescence curves were fitted to obtain the kinetic parameters of the main luminescence peaks, as shown in Table 3. Based on the provided kinetic parameter data, the high-temperature peak at 405K exhibits superior sensitivity. Because the lifetime of the capture center is essentially determined by the trap level depth and frequency factors, this luminescence peak exhibits significantly improved thermal stability due to its unique parameter combination.

[0120] Table 3NaYSrWO6:0.3u 3+ Kinetic parameters of the main luminescence peaks of the TL luminescence curve

[0121] Peak Activation energy, E / eV Frequency factor, s Reaction order, b Thermoluminescence peak temperature, TM / K 1 0.97 <![CDATA[2.9×10 11 ]]> 1.5 405 2 1.62 <![CDATA[2.5×10 17 ]]> 2.0 460 3 0.70 <![CDATA[2.4×10 9 ]]> 1.3 355 4 1.34 <![CDATA[3.9×10 10 ]]> 2.0 510

[0122] In order to analyze whether there is a low temperature peak, the NaYSrWO6:0.3Eu was measured after irradiation with an X-ray tube for 3 minutes (about 36mGy). 3+ The low-temperature two-dimensional thermoluminescence spectrum of the phosphor (ie, Example 7) from 100K to 550K (heating rate is 2K / s) is as follows: Figure 10 As shown, the sample NaYSrWO6:xEu was measured after irradiation with an X-ray tube for 3 minutes (about 36mGy). 3+ (x=0.005,0.01,0.05,0.1,0.2,0.3,0.5) low-temperature two-dimensional thermoluminescence spectra from 100K to 550K, the results are as follows Figure 10 As shown in the figure, it can be seen that in addition to the two thermoluminescence peaks above 300K, the sample also has a strong low-temperature thermoluminescence peak at around 225K. The thermoluminescence curves of the two thermoluminescence peaks above 300K are consistent with the previous ones. In contrast, the newly emerged low-temperature thermoluminescence peak shows a significant concentration-dependent feature. The low-temperature thermoluminescence peak around 225K increases with the concentration of Eu. 3+ The peaks in the low-temperature region correspond to shallow traps, which release trapped charge at relatively low temperatures, reflecting the rapid decay of the material. In contrast, deep traps require higher temperatures to release charge, reflecting the material's long-term energy storage.

[0123] 2.8 Three-dimensional thermoluminescence spectroscopy

[0124] To understand the effect of NaYSrWO6 doped with Eu 3+ The role of ions in the trap, the present invention tested NaYSrWO6:xEu 3+ (x=0.01, 0.1, 0.2, 0.3, 0.5), that is, the three-dimensional thermoluminescence spectra of the phosphors obtained in Example 3 and Examples 5-8 after 3 minutes of X-ray irradiation (about 18.6 mGy), the results are as follows Figure 11As shown. It can be seen that although the emission intensity of the samples is different, without exception, NaYSrWO6 is 3+ ions, the main emission peak is located near 615nm. This is consistent with the photoluminescence spectrum of the samples studied in this invention, which shows that Eu 3+ Ionic 5 D0→ 7 F2 transition is dominant in NaYSrWO6. In addition, its optimal emission temperature is around 400K. 3+ When the concentration of ions increases from x = 0.01 to x = 0.3, the emission peak of the sample at 615nm gradually increases and reaches the highest point at x = 0.3. 3+ When the concentration of ions increases from x=0.3 to x=0.5, the main emission peak of the sample at 615nm is gradually quenched.

[0125] The concentration of the sample with the best thermoluminescence intensity is different from the concentration of the best photoluminescence spectrum mentioned above, which is a normal phenomenon. 3+ When the addition of Eu is carried out, the thermoluminescence intensity of the sample changes significantly. 3+ The concentration of ions can well control the intensity of the sample's thermoluminescence.

[0126] In order to further analyze the characteristics of the low temperature peak, the NaYSrWO6:xEu obtained in Examples 1-8 was tested. 3+ The low-temperature three-dimensional thermoluminescence spectra (100-550K) of the phosphors (x=0.005, 0.01, 0.05, 0.1, 0.15, 0.2, 0.3, 0.5) after 3 minutes (about 18.6mGy) of X-ray excitation are as follows: Figure 12 As shown. It can be seen that as Eu 3+ When the doping concentration increases from 0.005 to 0.5, the low-temperature peak luminescence is located at 400nm-600nm, and the intensity of the low-temperature peak shows a significant downward trend, while the two high-temperature peak intensities show the characteristics of first enhancing and then saturating, reaching the maximum value at x=0.3. The trend of the high-temperature peak is consistent with the previous article. Here, we can compare the trap depth E calculated by the initial rise method and Chen's peak shape method. initial and E chen , to verify whether the low-temperature peak is thermally activated defect luminescence, the initial rise method is calculated using the following formula.

[0127] I(T)=Cexp(-E T / kT) (11)

[0128] In formula 11, C is a constant including the frequency factor s, and E Tis the depth of the trap level, K is the Boltzmann constant 8.62×10 -5 eV / K, the initial rise method data is selected from the low temperature peak rise stage (130-180K) to ensure that the trap is not exhausted. By plotting the relationship between ln(I) and 1 / T, the slope is -E T / k can get the trap depth. The result is as follows Figure 13 and as shown in Table 4.

[0129] Chen's peak shape method calculates the trap depth E through the geometric parameters of the thermoluminescence peak using the following formula.

[0130]

[0131] In Equation 12, E is the trap depth, k is the Boltzmann constant, and μ g is a numerical factor related to the shape of the thermoluminescence curve; τ is the low temperature half-width (T m -T1); δ is the high temperature half-width (T2-T m ); ω is the total length of the half-height width corresponding to the peak temperature (T2-T1); T1, T m and T2 are the temperature values ​​corresponding to half the intensity on the low temperature side, the peak temperature, and the temperature values ​​corresponding to half the intensity on the high temperature side, respectively. In Equation 12, α represents τ, δ, and ω, respectively. Substituting into Equations 13, 14, and 15 yields the value c ɑ and b ɑ .

[0132] After calculation, the trap depth E initial and E chen The relevant parameters are listed in Table 4.

[0133] c τ =1.51+3(μ g -0.42) b τ =1.58+4.2(μ g -0.42) (13)

[0134] c δ =0.96+7.3(μ g -0.42) b δ =0 (14)

[0135] c ω =2.52+10.2(μ g -0.42) b ω =1 (15)

[0136] Table 4. Relevant parameters of the trap calculated by Chen's method and initial rise method

[0137] τ δ ω <![CDATA[E chenτ ]]> <![CDATA[E chenδ ]]> <![CDATA[E chenω ]]> <![CDATA[E initial ]]> Example 2 24 34 24 0.20 0.21 0.21 0.21 Example 3 18 36 18 0.32 0.25 0.27 0.25 Example 4 20 36 20 0.28 0.24 0.26 0.24 Example 5 22 32 22 0.23 0.23 0.23 0.25 Example 6 18 34 18 0.32 0.26 0.28 0.26 Example 7 22 32 22 0.26 0.25 0.25 0.22 Example 8 20 34 20 0.30 0.27 0.28 0.22

[0138] According to the calculation, the results of the two methods are consistent. chenτ ≈E chenδ ≈E chenω ≈E initial The value is consistent with the shallow trap energy level. The low-temperature peak luminescence intensity first increases and then decreases with increasing temperature, and the trap depth is consistent with the activation energy of Arrhenius fitting in the previous article (0.214 eV), indicating that the two originate from the thermal activation process of the same defect energy level, proving that the luminescence of the low-temperature peak is thermally activated defect luminescence.

[0139] The low temperature peak is only in Eu 3+ After doping, Eu 3+ Doping introduces shallow traps, but the intensity of the low-temperature peak decreases with the 3+ The increase of doping concentration may be due to the high concentration of Eu 3+ Doping reduces oxygen vacancies in the matrix through charge compensation effect, weakening the intensity of thermally activated defect luminescence. At the same time, high concentration Eu 3+ New deep traps or non-radiative recombination centers may be introduced, resulting in an increase in the number of deep traps and a decrease in the number of shallow traps, which enhances the high-temperature peak and suppresses the luminescence of the low-temperature peak.

[0140] 2.9 Dose rate response

[0141] In order to determine the X-ray 3+ The linear response range of the phosphor is determined by using an X-ray tube at a fixed voltage of 50KV for NaYSrWO6:0.3Eu 3+ The phosphor was irradiated at a dose rate of 0.266 to 2.1 Gy / min. The luminescence spectra of the samples at different dose rates were obtained as follows: Figure 14 As shown in part (a) of the figure. Then, by continuously increasing the irradiation dose rate of the X-ray radiation source from 0.266Gy / min to 2.1Gy / min, it can be seen that there is indeed a good positive linear relationship between the sample RL intensity and the X-ray irradiation dose rate in the range of 0.266Gy / min to 2.1Gy / min. The fitting results are shown in Figure 14 As shown in part (b), the linear regression equation is Y = 34367.14X + 7562.97, and the linear fitting parameter is R 2 =0.99878. This indicates that there is a good linear relationship between the RL intensity of the sample and the X-ray irradiation dose rate. In addition, the RL curves of the sample at different dose rates Figure 14 From part (c), it can be seen that the sample can be filled with X-rays in a short time and remains stable after being filled, and the decay time is short after the irradiation stops.

[0142] 2.10 Repeatability test

[0143] In order to study the repeatability of the thermoluminescence intensity of the phosphor obtained in the present invention, the NaYSrWO6:0.3Eu obtained in Example 7 was used to 3+ The phosphor was irradiated and measured repeatedly, and the changes in thermoluminescence intensity were observed. X-rays were irradiated at a constant dose of 3.6 mGy, and then linearly heated from room temperature to 550 K at a heating rate of 5 K / s, and the thermoluminescence curve was recorded. The experiment was carried out for a total of 25 complete cycles of the "irradiation-heating-measurement" process, and the thermoluminescence integral intensity obtained in each measurement was used as the measurement value. Figure 15 As shown in the figure, the relative standard error of these 25 measurements is 2.2%. Therefore, it can be considered that the sensitivity of the material is less affected by irradiation and heating. It also shows that the crystal structure of the material is not damaged during multiple irradiation and heating, and the energy level structure of the trap center is relatively stable. In summary, it can be seen that the sample has a good and sensitive response to X-rays and has good stability to X-rays. This is NaYSrWO6:0.3Eu 3+ Phosphors offer the potential for real-time dose rate measurement.

[0144] In addition to the good linear relationship between radiation dose rate and radiation luminescence intensity and good radiation resistance stability, tungstate has a heavy element component W (Z = 74), which has good X-ray cutoff ability. The sample responds quickly and has short attenuation at different dose rates, and has potential application value in X-ray imaging.

[0145] The above are merely preferred embodiments of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A single Eu-doped perovskite phosphor, characterized in that: The molecular formula is NaYSrWO6:xEu 3+ , wherein x=0.005-0.

5.

2. The method for preparing a single Eu-doped perovskite phosphor according to claim 1, wherein: The following steps are involved: The raw materials are weighed according to the stoichiometric ratio, mixed and ground, and the obtained powder is preheated and then rapidly heated and calcined. After the calcination, the powder is crushed and ground to obtain the single-doped Eu perovskite phosphor.

3. The method for preparing a single Eu-doped perovskite phosphor according to claim 1, characterized in that: The raw materials include tungsten trioxide, yttrium oxide, strontium salt, sodium salt and europium oxide.

4. The method for preparing a single Eu-doped perovskite phosphor according to claim 1, characterized in that: The strontium salt is strontium carbonate.

5. The method for preparing a single Eu-doped perovskite phosphor according to claim 1, characterized in that: The sodium salt is sodium carbonate.

6. The method for preparing a single Eu-doped perovskite phosphor according to claim 1, characterized in that: The preheating temperature is 900° C. and the preheating time is 1 hour.

7. The method for preparing a single Eu-doped perovskite phosphor according to claim 1, characterized in that: The calcination temperature is 1200° C. and the calcination time is 8 hours.

8. Use of the single Eu-doped perovskite phosphor according to claim 1 in X-ray imaging.

9. Use of the single Eu-doped perovskite phosphor according to claim 1 in LED lighting.

10. Use of the single Eu-doped perovskite phosphor according to claim 1 in radiation dose measurement.

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