Sm < 3 + >-doped Sr2GaTaO6 fluorescent powder and preparation method thereof

Abstract

The invention discloses Sm < 3 + > doped Sr2GaTaO6 fluorescent powder and a preparation method thereof, and belongs to the technical field of fluorescent materials. The chemical formula of the fluorescent powder is Sr2-x% GaTaO6: x% Sm < 3 + >, x is the doping molar weight of Sm < 3 + >, and x is greater than or equal to 1 and less than or equal to 7. The preparation method comprises the following steps: weighing raw materials of SrCO3, Ga2O3, Ta2O5 and Sm2O3 according to the chemical formula, grinding and then carrying out high-temperature sintering, and the obtained fluorescent powder is high in luminous efficiency and good in thermal stability and is a novel multifunctional material with wide application prospects in the fields of white light illumination and optical temperature measurement.

Description

Technical Field

[0001] This invention belongs to the field of fluorescent materials technology, and particularly relates to a Sm 3+ Doped Sr2GaTaO6 phosphor and its preparation method. Background Technology

[0002] White light-emitting diodes (WLEDs), as cutting-edge high-efficiency lighting and optoelectronic devices, have been widely used in various fields such as general lighting, smart display devices, and plant factories due to their significant advantages, including long lifespan, low power consumption, ecological sustainability, high power efficiency, and long-term stability. Currently, the mainstream commercial technology route for WLED manufacturing is: using Y3Al5O... 12 Ce 3+ (YAG:Ce 3+ White light output is achieved by coating InGaN chips with phosphors or by using blue LED chips with yellow phosphors. However, this approach has inherent drawbacks: a poor color rendering index (CRI) and a high correlated color temperature (CCT) (typically >4500K). The core issue lies in the lack of red components in the spectrum, which limits the application of WLEDs in scenarios with high color rendering quality requirements.

[0003] To overcome this technical limitation and improve the CRI, color stability, and color gamut of WLEDs, a synergistic optimization scheme involving multi-color phosphors and light sources is needed. For example, using SrS:Eu... 2+ Red phosphor, SrGa2S4:Eu 2+ The combination of green phosphors and the ultraviolet-blue light emitted by InGaN chips can significantly improve the optical performance of devices. Among them, red-emitting phosphors (or glass phosphors) are particularly important for achieving high-performance WLEDs, as key materials for completing the red component of the spectrum. Although phosphor materials play a central role in improving WLED performance, most phosphors currently used in WLED systems still fall short of the ideal requirements for performance optimization, and there is room for improvement in luminous efficiency and stability.

[0004] Samarium (Sm 3+ Its fluorescence spectrum covers the visible to near-infrared region, and its energy level structure is complex, possessing a ground state. 6 H J and 6 F J Multistates and excited states 4 G 5 / 2 Energy levels are excellent activators that produce orange-red emission in various inorganic matrices. To date, researchers have studied the properties of various AA'BTaO6 type phosphors: among which, Sr2ScTaO6:Sm 3+The phosphor exhibits excellent thermal stability, maintaining 85% of its emission intensity at 423 K compared to room temperature; SrLaMgTaO6:Sm 3+ It contains groups ranging from TaO6 to Sm 3+ Energy transfer, through the regulation of Sm 3+ Tunable luminescence can be achieved by adjusting the doping concentration; Ca2GaTaO6:Sm 3+ The phosphor exhibits good performance, with a luminescence intensity at 423K that is 88.17% of that at 298K; Sr2InTaO6:Sm 3+ These materials possess high CRI and an internal quantum efficiency (IQE) of up to 67.1%, and all of them show potential application prospects in the field of luminescent material preparation.

[0005] Double perovskite compounds, with the molecular formula AA'BB'O6, are widely used due to their excellent chemical and physical properties. Sr2GaTaO6, a typical representative of double perovskite compounds, differs from traditional matrices such as borates, phosphates, and silicates in that its double perovskite structure contains two alternating octahedrons (BO6 and B'O6), which can induce local lattice modulation and reduce the local symmetry of the A-site, thus providing Sm... 3+ Ion doping provides diverse site environments, giving it a natural advantage as a phosphor matrix. To date, no Sm... 3+ There are reports on Sr2GaTaO6 doped phosphor materials, and existing WLEDs still have problems such as weak thermal stability and limited material functionality. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes a Sm 3+ A Sr₂GaTaO₆ doped phosphor and its preparation method were developed. This phosphor exhibits high luminous efficiency and good thermal stability. It is of great significance for overcoming the shortcomings of existing technologies and promoting the performance upgrade of WLEDs.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A kind of Sm 3+ Doped Sr₂GaTaO₆ phosphor, with the chemical formula Sr 2-x% GaTaO6:x%Sm 3+ Where x is Sm 3+ The molar amount of doping, and 1≤x≤7.

[0009] All phosphors belong to the cubic crystal system with space group Pm-3m and have a stable crystal structure. They exhibit strong orange-red emission under 408nm light excitation (with the main emission peak at 602nm), demonstrating excellent color stability and purity. They also exhibit outstanding thermal stability, retaining 97.10% of the emission intensity at room temperature (activation energy 0.211eV) at 450K, and have high internal quantum efficiency. They possess both luminescence and optical temperature measurement functions, providing a novel multifunctional material for white light illumination and optical temperature measurement.

[0010] Furthermore, x is 1, 2, 3, 4, 5, 6, or 7.

[0011] This invention clarifies the value of x, covering the effective doping concentration range. At each concentration, it avoids the problems of "insufficient luminescence intensity due to excessively low concentration" or "quenching due to excessively high concentration", ensuring that the phosphor can stably achieve orange-red emission, good color stability and thermal stability, and adapt to the performance requirements of different application scenarios.

[0012] Furthermore, x is 4.

[0013] The concentration is Sm 3+ The optimal doping level yields the strongest phosphor emission intensity, a color purity of 90.43%, and a color coordinate closer to the red region; it also provides optimal thermal stability and optical temperature measurement performance (relative sensitivity S). r =0.811%K -1 Absolute sensitivity S a =0.341K -1 This is the optimal solution that balances luminous efficiency, color quality, thermal stability, and temperature measurement performance.

[0014] The present invention also provides the Sm 3+ The preparation method of doped Sr2GaTaO6 phosphor includes the following steps:

[0015] a. Using SrCO3, Ga2O3, Ta2O5, and Sm2O3 as raw materials, according to the stated chemical formula Sr 2-x% GaTaO6:x % Sm 3+ Weigh each raw material according to its stoichiometric ratio;

[0016] b. Mix and grind the weighed raw materials evenly;

[0017] c. The ground mixture is placed in a muffle furnace and sintered at high temperature to obtain the Sm 3+ Doped with Sr2GaTaO6 phosphor.

[0018] This invention employs a high-temperature solid-state method involving "weighing-grinding-high-temperature sintering," which is simple, convenient, and highly repeatable, making it suitable for large-scale production. The rationally designed steps ensure that the raw materials react fully, successfully producing a target phosphor with high crystallinity and uniform performance, guaranteeing that the product meets the application requirements for white light illumination and optical temperature measurement.

[0019] Furthermore, the purity of SrCO3, Ga2O3, Ta2O5 and Sm2O3 is 99.99%.

[0020] High-purity raw materials avoid the introduction of impurities, reduce the interference of impurities on the phosphor's luminescence center, and ensure that luminous efficiency, color stability, and thermal stability are not affected by impurities; ensure the performance consistency of different batches of products, improve product reliability, and provide a stable material basis for subsequent applications (such as WLED packaging).

[0021] Furthermore, the grinding time is 30 minutes.

[0022] Limiting the grinding time ensures uniform mixing and consistent composition of raw materials, avoiding incomplete crystallization and performance fluctuations in the sintered product due to uneven mixing; it also creates conditions for the full reaction of each component during the subsequent high-temperature sintering process, improving the uniformity and performance stability of the phosphor product.

[0023] Furthermore, the specific operation steps of the high-temperature sintering are as follows: pre-sintering is carried out by heating from room temperature to 600°C and holding for 2 hours, then heating to 1300°C and holding for 8 hours for final sintering, and after sintering, the product is naturally cooled to room temperature and then ground into powder.

[0024] Pre-sintering can remove volatiles or impurities from the raw materials, and the final sintering temperature and time ensure the complete formation of the crystal structure; natural cooling avoids lattice defects caused by sudden temperature changes, and subsequent grinding makes the product a uniform powder, further optimizing the luminescent performance and adapting it to practical application scenarios such as WLED packaging and optical temperature measurement.

[0025] The present invention also provides a Sm 3+ Application of doped Sr2GaTaO6 phosphor in the fabrication of white light-emitting diodes.

[0026] The present invention also provides a Sm 3+ Application of Sr2GaTaO6 doped phosphor in optical thermometry.

[0027] Compared with the prior art, the present invention has the following advantages and technical effects:

[0028] The Sm prepared by this invention 3+ Sr2GaTaO6 phosphor under 408nm light excitation, Sm 3+The optimal doping concentration is 4 mol%, at which point a strong orange-red emission peak appears at 600 nm, exhibiting excellent color stability and color purity. Thermal stability testing shows that when the temperature rises to 450 K, the phosphor retains 97.10% of its room-temperature emission intensity under a relatively high activation energy (0.211 eV), demonstrating excellent stability. Furthermore, the phosphor has an internal quantum efficiency of 27.10%, exhibiting good luminescent performance. When packaged with a 410 nm chip and commercial green and blue phosphors to form a white light-emitting diode, the device exhibits excellent correlated color temperature (CCT) and a high color rendering index (CRI). Simultaneously, the phosphor also possesses optical thermometric properties, with a temperature sensing sensitivity of S0. r and S a 0.811%K -1 and 0.341K -1 In conclusion, Sm 3+ Doped Sr2GaTaO6 phosphors are a new type of multifunctional material with broad application prospects in both white light illumination and optical temperature measurement. Attached Figure Description

[0029] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0030] Figure 1 (a) represents Sm doping with different concentrations. 3+ Sr 2-x% GaTaO6:x%Sm 3+ XRD pattern of phosphor; (b) Crystal structure of Sr2GaTaO6; (c) Sr2GaTaO6:0%Sm 3+ Rietveld structure refinement and crystal structure; (d) is Sr 1.96 GaTaO6:4%Sm 3+ Rietveld structure refinement and crystal structure;

[0031] Figure 2 (a) represents Sm doping with different concentrations. 3+ Sr 2-x% GaTaO6:x%Sm 3+ (a) Excitation spectrum of phosphor (detection wavelength 602 nm); (b) Sm doping at different concentrations 3+ Sr 2-x% GaTaO6:x%Sm 3+ (c) Emission spectrum of phosphor (excitation wavelength 408 nm); (d) Sm+ doped with different concentrations 3+ Sr 2-x% GaTaO6:x%Sm3+ The relationship between logarithm lg(I / x) and lgx in phosphors; (d) shows the variation of emission intensity of ED and MD transitions with doping concentration; (e) shows the relationship between Sm and other phosphors with different doping concentrations. 3+ Sr 2-x% GaTaO6:x%Sm 3+ Phosphors in different Sm 3+ Color development characteristics at different doping concentrations; (f) shows the color development characteristics of Sm at different doping concentrations. 3+ Sr 2-x% GaTaO6:x%Sm 3+ Phosphors in different Sm 3+ Analysis of the x and y coordinates of the colorimetric index under different doping concentrations;

[0032] Figure 3 (a) in the text is Sm 3+ (a) Ion energy level transition diagram; (b) is Sr 1.96 GaTaO6:4mol%Sm 3+ IQE of phosphor; (c) is Sr 1.96 GaTaO6:4mol%Sm 3+ Fluorescence lifetime diagram of phosphor;

[0033] Figure 4 (a) in the text is Sr 1.96 GaTaO6:4mol%Sm 3+ (a) The emission intensity of the phosphor changes with increasing temperature; (b) is the emission intensity of Sr. 1.96 GaTaO6:4mol%Sm 3+ Contour distribution of the thermal stability of phosphors; (c) is Sr 1.96 GaTaO6:4%Sm 3+ Thermal stability line graph of phosphor; (d) is Sr 1.96 GaTaO6:4%Sm 3+ Thermal quenching mechanism of phosphor; (e) is ln[(I0 / I T (f) is a schematic diagram of the relationship between Sr and 1 / T; 1.96 GaTaO6:4%Sm 3+ The evolution of the color coordinates of phosphors with temperature;

[0034] Figure 5 (a) in the text is Sr 1.96 GaTaO6:4%Sm 3+ fluorescent powder 4 G 5 / 2 → 6 H J (J=5 / 2, 9 / 2, 11 / 2) Changes in transition peak intensity with increasing temperature; (b)4 G 5 / 2 → 6 H 7 / 2 and 4 G 5 / 2 → 6 H J (J=5 / 2, 9 / 2, 11 / 2) Fluorescence intensity ratio (FIR) fitting; (c) and (d) S calculated at different temperatures. a and S r ;

[0035] Figure 6 (a) shows the CIE coordinates and equal energy point of the white light emitting diode (WLED), and the inset is a photograph of the fabricated white light emitting diode; (b) shows the electroluminescence spectrum generated by the white light emitting diode under different current driving conditions, and the inset shows the Ra value of the white light emitting diode under different current driving conditions. Detailed Implementation

[0036] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0037] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0038] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0039] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0040] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0041] This invention uses a high-temperature solid-state method to prepare Sm 3+ Doping Sr2GaTaO6 phosphor, the target product has the chemical formula Sr 2-x% GaTaO6:x%Sm 3+ (where x is Sm) 3+ The molar amount of doping satisfies 1 ≤ x ≤ 7, preferably x is 1, 2, 3, 4, 5, 6 or 7, and most preferably x is 4; where x in this chemical formula actually represents the molar percentage doping amount, for ease of understanding and illustration, "%" is placed in the general chemical formula, and can also be represented as Sr 2-x GaTaO6:xSm 3+ (0.01≤x≤0.07) This phosphor belongs to the cubic crystal system and has the space group Pm-3m.

[0042] The specific experimental steps are as follows:

[0043] 1. Accurate weighing of raw materials: SrCO3, Ga2O3, Ta2O5, and Sm2O3, all with a purity of 99.99%, were selected as reaction raw materials. The chemical formula of the target product, Sr, was determined. 2-x% GaTaO6:x%Sm 3+ The corresponding stoichiometric ratio is determined by using weighing instruments with the required precision to accurately weigh the mass of each raw material, ensuring that the raw material ratio is accurate.

[0044] 2. Mixing and grinding: Place all weighed raw materials into a grinding container and mix and grind them using a suitable grinding method. The grinding time should be controlled at 30 minutes until the raw materials are fully mixed and homogeneous, resulting in a fine and uniform powder.

[0045] 3. High-temperature segmented sintering: The uniformly ground mixed powder is placed in a muffle furnace for high-temperature segmented sintering. First, the temperature is raised from room temperature to 600℃ and held for 2 hours to complete pre-sintering. After pre-sintering, the temperature is raised to 1300℃ and held for 8 hours for final sintering. After the sintering process is completed, the muffle furnace is closed and the product in the furnace is allowed to cool naturally to room temperature.

[0046] 4. Post-processing of the product: After the sintered product cools to room temperature, it is taken out and placed in a grinding container, and ground again until it becomes a uniform powder, thus obtaining Sm. 3+ Finished product of Sr2GaTaO6 doped phosphor.

[0047] The Sm 3+ Doped Sr2GaTaO6 phosphors can be used in the fabrication of white light-emitting diodes or optical temperature measurement.

[0048] Unless otherwise specified, "room temperature" in this invention refers to 25±2℃.

[0049] All raw materials used in this invention were purchased from the market.

[0050] The technical solution of the present invention will be further illustrated by the following embodiments.

[0051] Example 1

[0052] A kind of Sm 3+ Doped Sr2GaTaO6 phosphor (Sr 1.99 GaTaO6:1%Sm 3+ The preparation method for (i.e., x=1) involves the following steps:

[0053] a. Using SrCO3 (99.99% purity), Ga2O3 (99.99% purity), Ta2O5 (99.99% purity), and Sm2O3 (99.99% purity) as raw materials, according to Sr 1.99 GaTaO6:1%Sm 3+ Weigh each raw material according to its stoichiometric ratio;

[0054] b. Place the weighed raw materials in an agate mortar and add 4mL of alcohol, then grind thoroughly for 30 minutes.

[0055] c. Place the ground mixture in a muffle furnace and heat it from room temperature to 600°C at a rate of 5°C / s. Hold the temperature at 600°C for 2 hours to complete pre-sintering. After pre-sintering, continue heating to 1300°C and hold for 8 hours for final sintering. After sintering, close the muffle furnace and allow the product to cool naturally to room temperature. Remove the product and place it in a grinding container, then grind it again until it becomes a uniform powder to obtain Sm. 3+ Doped with Sr2GaTaO6 phosphor.

[0056] Example 2

[0057] Same as Example 1, except that x=2 and the chemical formula is Sr. 1.98 GaTaO6:2%Sm 3+ .

[0058] Example 3

[0059] Same as Example 1, except that x=3 and the chemical formula is Sr. 1.97 GaTaO6:3%Sm 3+ .

[0060] Example 4

[0061] Same as Example 1, except that x=4 and the chemical formula is Sr.1.96 GaTaO6:4%Sm 3+ .

[0062] Example 5

[0063] Same as Example 1, except that x=5 and the chemical formula is Sr. 1.95 GaTaO6:5%Sm 3+ .

[0064] Example 6

[0065] Same as Example 1, except that x=6 and the chemical formula is Sr. 1.94 GaTaO6:6%Sm 3+ .

[0066] Example 7

[0067] Same as Example 1, except that x=7 and the chemical formula is Sr. 1.93 GaTaO6:7%Sm 3+ .

[0068] Comparative Example 1

[0069] Same as Example 1, except that x=0 and the chemical formula is Sr2GaTaO6:0%Sm 3+ .

[0070] 1. XRD Analysis

[0071] Figure 1 (a) shows Sm doping concentrations of different amounts. 3+ Sr 2-x% GaTaO6:x%Sm 3+ XRD results of the phosphors (the phosphors prepared in Examples 1-7 and Comparative Example 1). The results show that the synthesized Sr 2-x% GaTaO6:x%Sm 3+ The main diffraction peaks of the series of phosphor samples matched the main diffraction peak of Sr2GaTaO6 standard card number 00-050-1735, and there was no significant deviation in the main peaks, indicating that Sr2GaTaO6 phosphor was successfully synthesized. This phosphor has a cubic crystal structure corresponding to the Pm-3m(211) space group, with lattice parameters a=b=c=3.942376Å, α=β=γ=90°, V=61.27Å3, Z=1.

[0072] Figure 1 The illustration in (b) shows a three-dimensional structural diagram of Sr₂GaTaO₆, from which its structural features can be clearly observed. Within the Sr₂GaTaO₆ framework, Ga… 3+ Ta 5+Each of the six oxygen atoms coordinates with one of the six oxygen atoms, forming two octahedral structures: [SrO6] and [TaO6]. These two types of octahedrons are interconnected by alternating oxygen atoms at their vertices, forming a complex network. Sr... 2+ The ions are located in the interstitial positions of the [GaO6] and [TaO6] octahedra, coordinating with the surrounding 8 O atoms to ultimately form the [SrO8] polyhedron. To determine the Sm content in the Sr2GaTaO6 matrix... 3+ The occupancy of ions can be determined by calculating Sm. 3+ This is achieved through the difference in ionic radii (denoted by Dr) between ions, and the specific calculation formula is as follows:

[0073]

[0074] In the formula, CN is the coordination number, and R... p R represents the radius of the matrix cation. q Indicates Sm doping 3+ Ionic radius. Considering the similarity between ionic radius and valence state (Sr... 2+ The ionic radius of Ga is 1.18 Å (coordination number CN=8). 3+ The ionic radius of Ta is 0.62 Å (CN=6). 5+ The ionic radius is =0.64 Å (CN=6), Sm 3+ The ionic radius is 1.079 Å (CN=6), and Dr is calculated to be 93.31%. Therefore, Sm 3+ More likely to replace Sr 2+ This achieves unit point occupancy. Furthermore, to study the perovskite stability of this matrix, this invention uses the tolerance factor (Tf) stability formula proposed by Goldschmidt, where Tf is the tolerance factor (Tf) stability formula. f A value close to 1 indicates that the structure of this double perovskite matrix is ​​very stable.

[0075]

[0076] Where R A For Sr 2+ Ionic radius, R X For O 2- Ionic radius, R M With R M’ Ga 3+ and Ta 5+ The ionic radius of Sr₂GaTaO₆ was calculated. f The value of 1.13 indicates that the matrix structure has double perovskite stability.

[0077] To further understand Sm 3+The effect of entering the crystal lattice on the material structure, this invention focuses on Sr2GaTaO6:0mol%Sm 3 + and Sr 1.96 GaTaO6:4mol%Sm 3+ Rietveld refinement was performed using Jade software, and the results are as follows: Figure 1 As shown in (c) and (d), the experimental data are represented by black dots, the calculated fitting curve is represented by a red line, the green line is the deviation between the experimental values ​​and the fitted data, and the short blue vertical line is the theoretical Bragg reflection position of the standard card pdf. The inducing factors of the refined crystal structure parameters are 7.18% and 7.82%, respectively. The increase in the inducing factor may be related to Sm 3+ The increase in ion doping concentration is related to the lower doping factor, which also indicates that the results are reliable.

[0078] 2. Photoluminescence characteristics analysis

[0079] Monitoring of Sm doping concentrations at 602 nm at room temperature 3+ Sr 2-x% GaTaO6:x%Sm 3+ The phosphor (the phosphor prepared in Examples 1-7) was used to obtain the PLE spectrum as shown below. Figure 2 In (a), a set of sharp excitation peaks can be observed in the 350nm-500nm range, specifically at 365nm, 380nm, 408nm, 421nm, 440nm, 465nm, and 480nm. This is consistent with Sm 3+ This is a typical 4f-4f transition correlation. The corresponding energy level transition is the ground state (6H). 5 / 2 → Excited state ( 3 F 9 / 2 , 4 K 11 / 2 4F 7 / 2 、( 6 P, 4 P) 5 / 2 , 4 G 9 / 2 , 4 I 13 / 2 and 4 I 11 / 2 The highest excitation peak intensity was observed at 408 nm, indicating that ultraviolet to blue-violet light can effectively excite the phosphor and that this excitation wavelength matches that of commercial WLED chips. This means the phosphor can be well excited by a 405 nm UV InGaN chip. Therefore, Sr 2-x% GaTaO6:x%Sm 3+ Phosphors have great application potential in the field of WLEDs.

[0080] Figure 2 (b) shows the results of Sm doping with different concentrations under 408 nm excitation. 3+ Sr 2-x% GaTaO6:x%Sm 3+ The PL spectra of the phosphors (the phosphors prepared in Examples 1-7) are shown. Four independent emission peaks can be observed at 565 nm, 602 nm, 647 nm, and 710 nm, corresponding to Sm 3+ Ion transition to 4 G 5 / 2 → 6 H J (J=5 / 2, 7 / 2, 9 / 2, 11 / 2), it is obvious that the emission peak with the best intensity under 408nm excitation is at 602nm.

[0081] from Figure 2 (c) It can be seen that, with Sm 3+ With increasing ion doping concentration, Sm 3+ The emission peak exhibits a concentration quenching phenomenon, with the emission intensity initially increasing and then decreasing. This is attributed to Sm 3+ After reaching the strongest emission at a doping concentration of 4%, further doping with Sm 3+ This will enhance the interaction between luminescent centers, thereby increasing the probability of nonradiative transitions and leading to a decrease in emission intensity.

[0082] To further investigate Sm in Sr2GaTaO6 3+ The energy transfer (ET) mechanism between ions was analyzed using the Dexter and Schulman models to calculate the luminescence intensity (I) versus Sm. 3+ The relationship between doping concentration (x):

[0083]

[0084] x Sm3+ I is the concentration of ion doping, I is the relative intensity of the emission peak, Q is the parameter for a specific type of electric multipole interaction, and A is the fitting parameter. Among them, Q=6 represents dipole-dipole (dd), Q=8 represents dipole-quadrupole (dq), and finally quadrupole-quadrupole (qq) interaction is represented by Q=10. Figure 2 (c) in the text shows Sm 3+ A linear relationship between ion concentration and log(I / x) versus log(x), where R... 2 The value is 0.99, the slope is -1.45755, corresponding to -Q / 3, therefore Q=4.373. This corresponds to a dipole-dipole (dd) interaction, which is close to the theoretical value of 6. This indicates that Sm 3+The orange-red emission quenching mechanism of doped Sr2GaTaO6 is mainly caused by nonradiative energy transfer due to dipole-dipole interactions.

[0085] To further analyze Sm 3+ According to the selection rules, for ion energy level transitions, in electric dipole (ED) transitions, the difference (ΔJ) between the two energy levels before and after the transition can be 0, ±1, ±2, ±3, ±4, ±5, or ±6 (absolute value ≤ 6). When ΔJ = 2, 4, or 6, if J or J' = 0, then the ED transition is forbidden. Magnetic dipole (MD) transitions obey ΔJ = 0, ±1. Therefore, it can be known that the transitions occurring at 647 nm... 4 G 5 / 2 → 6 H 9 / 2 The transition is an electric dipole (ED) transition, at 565 nm. 4 G 5 / 2 → 6 H 5 / 2 The transition is classified as a magnetic dipole (MD) transition, located at 602 nm. 4 G 5 / 2 → 6 H 7 / 2 The transition is a hybrid electric dipole (ED / MD) transition.

[0086] Due to Sm 3+ of 4 G 5 / 2 → 6 H J The transition satisfies the electric dipole transition selection rule for the ff transition, and the excited state 4 G 5 / 2 It possesses characteristics of long lifetime and low nonradiative relaxation loss, and its transition probability is much higher than other nonradiative relaxation paths, ensuring that electrons can efficiently release energy through radiative transitions, resulting in a significant increase in the intensity of orange-red emission. According to the Judd-Ofelt theory, the intensity ratio between ED and MD transitions can be called the asymmetric ratio, when... 4 G 5 / 2 → 6 H 9 / 2 (ED) transition and 4 G 5 / 2 → 6 H 5 / 2 When the ratio of (MD) transitions is greater than 1, it indicates that Sm 3+ Ions located at non-centrosymmetric positions within the Sr2GaTaO6 lattice, such as... Figure 2 As shown in (d) in the figure. The symmetry of this structure is indicated by the ED strength and MD strength, i.e.:

[0087]

[0088] Figure 2 (e) shows the excitation at 406 nm with different concentrations of Sm 3+ Sr 2-x% GaTaO6:x%Sm 3+ The color coordinate changes of the phosphors (the phosphors prepared in Examples 1-7) clearly show that the color coordinates of the phosphors only shift slightly with temperature changes, and the CIE color coordinate positions of each sample are almost the same.

[0089] Figure 2 (f) represents Sm doping at different concentrations. 3+ Sr 2-x% GaTaO6:x%Sm 3+ The CIE coordinate transformation graphs of the phosphors (the phosphors prepared in Examples 1-7) clearly show the different concentrations of Sr. 2-x% GaTaO6:x%Sm 3+ From the color coordinates, we can find Sr 1.96 GaTaO6:4mol%Sm 3+ It is closer to the red region, therefore, WLED orange-red emission has certain application value.

[0090] Furthermore, color temperature and color purity are also important parameters for judging the color quality of luminescent materials. Therefore, the correlated color temperature (CCT) value can be evaluated using the McCamy equation, as follows:

[0091]

[0092]

[0093] Where x and y are Sr 2-x GaTaO6:xSm 3+ The color coordinate position of Sr, in order to further explore 2-x% GaTaO6:x%Sm 3 + The color quality of fluorescent pink can be calculated using the following formula:

[0094]

[0095] Among them, (x i y i ), (x w y w ) and (x z y z The coordinates () represent the sample color coordinates, the standard white light source coordinates (0.333, 0.333), and the color coordinates corresponding to the dominant wavelength, respectively. Table 1 shows the color coordinates of different concentrations of Sm 3+The CIE coordinates of Sr₂GaTaO₆ doped with Sm₂ are shown, along with the calculated CCT and color purity. The results indicate that in the color temperature range of 1710-1717 K, when doped with 4% Sm₂... 3+ The color purity reached 90.43%, Sm 3+ The activated Sr2GaTaO6 phosphor exhibits excellent color purity.

[0096] Table 1

[0097]

[0098] like Figure 3 As shown in (a) above, when Sm 3+ When ions are situated within a crystal matrix, the energy level structure of their 4f electron shells forms a series of discrete energy levels due to crystal field splitting. When the photon energy provided by an external light source matches the energy difference of a certain energy level transition, Sm 3+ It absorbs photons through ff electron transitions. Electrons are excited from the stable ground state to these high-energy excited states, completing the light absorption process.

[0099] Subsequently, electrons in the high-energy excited state, due to their high energy and poor stability, will rapidly relax to lower energy levels through nonradiative transitions (NR), eventually converging to the lowest excited state. 4 G 5 / 2 (Energy approximately 17,500-18,000 cm⁻¹) -1 When electrons are in 4 G 5 / 2 Once a certain number of energy levels have accumulated, photons will be released through radiative transitions, returning to a lower energy level. 6 H J (J = 5 / 2, 7 / 2, 9 / 2, 11 / 2) energy levels, eventually returning to the ground state.

[0100] Internal quantum efficiency (IQE) is an important indicator for evaluating the photoelectric conversion capability of optoelectronic devices, and therefore can well demonstrate the application value of phosphors in lighting equipment. Internal quantum efficiency (IQE) is expressed by the following formula:

[0101]

[0102] Where η is the internal quantum efficiency (IQE) value, and LS is the Sr 1.96 GaTaO6:4%Sm 3+ The emission spectrum of the phosphor, where ER represents the excitation spectrum of the reference BaSO4 (BSO), and ES is the excitation spectrum of the phosphor sample. For example... Figure 3 As shown in (b), when excited at 408 nm, Sr 1.96 GaTaO6:4%Sm 3+The IQE of the phosphor, calculated using the above formula, is approximately 27.1%, slightly higher than other Sm... 3 + Doped matrix, such as Bi4Sr3Te5O 19 0.02Sm 3+ (17.23%) and Ba2La8(SiO4)6O2:0.1Sm 3+ (22.59%, Li2NaBP2O8:0.03Sm) 3+ (25.3%) and NaSrLa(MoO4)O3:0.04Sm 3+ (23.12%).

[0103] Figure 3 (c) reveals that fluorescence decay is a decay mode characterized by rapid initial decay followed by gradual decay until stabilization. Due to Sm 3+ Since there is only one launch center, the sample decay process can be appropriately explained by the following equation using a single exponential function for fitting:

[0104]

[0105] Where I(t) represents the decay intensity of the sample at time t, A represents the fitting constant, t represents the measurement time, and τ represents the decay lifetime value. The Sr value is obtained through fitting. 1.96 GaTaO6:4%Sm 3+ The decay time is 0.998 ms. The short decay time is very suitable for WLEDs.

[0106] 3. Thermal stability analysis

[0107] WLEDs operate at temperatures above room temperature in practical applications, making the thermal stability assessment of phosphors crucial. For example... Figure 4 As shown in (a), as the temperature gradually increases from 300K to 500K, by collecting Sr 1.96 GaTaO6:4%Sm 3+ The emission spectrum of the phosphor excited at 408 nm. It can be seen that as the temperature increases, the intensity of the emission peak at 602 nm shows significant stability, and the shape and energy distribution of each emission peak are consistent.

[0108] Figure 4 (b) in the text is Sr 1.96 GaTaO6:4%Sm 3+ The contour plot of phosphor thermal stability shows that the phosphor intensity decreases slightly as the temperature rises. This is because the increase in temperature causes an increase in non-radiative transitions, which in turn reduces the phosphor intensity.

[0109] Sr1.96 GaTaO6:4%Sm 3+ The excellent thermal stability of phosphors can be clearly seen from... Figure 4 (c) shows that the phosphor intensity is 97.10% of the room temperature phosphor intensity when the temperature reaches 450K, and remains at 95% when the temperature is 500K. Furthermore, the characteristic temperature (T0.5) means that the phosphor intensity at the characteristic temperature is 50% of the room temperature phosphor intensity, while Sr... 1.96 GaTaO6:4%Sm 3 + The T0.5 is significantly higher than that at 500K. Meanwhile, Sr... 1.96 GaTaO6:4%Sm 3+ It maintained 95% of its luminescence intensity at 500K, which is higher than that of Y₂O₃:Eu. 3+ (480K, @50.04%) and Sr2Si5N8:Eu 2+ The phosphor content (480K, @69.94%) is much higher than that of commercial red phosphors, which means that the phosphor prepared in this invention exhibits excellent stability in LED operating environments and has potential value in WLED applications.

[0110] Sr 1.96 GaTaO6:4%Sm 3+ The luminescence properties of phosphors as a function of temperature and their thermal quenching effect can be elucidated using a configurational coordinate model (the horizontal axis represents the spatial configuration of the ions, and the vertical axis reflects the energy level of the system), such as... Figure 4 As shown in (d) in the figure. Under normal temperature conditions, when using a photoexcitation material with a wavelength of 408 nm, Sm 3+ Ions in ground state 6 H 5 / 2 The electrons will first absorb energy and transition to an excited state. 4 F 7 / 2 Subsequently, these electrons decay to a metastable state through nonradiative transitions (NR). 4 G 5 / 2 Subsequently, electrons release energy through radiative transitions (i.e., "process ①"), emitting visible light of different wavelengths, and eventually return to the ground state, thus enabling the material to emit light normally.

[0111] When the ambient temperature rises, the system gains additional heat energy. At this point, it is in a metastable state. 4 G 5 / 2 Some electrons absorb this thermal energy, and with enough energy, they break through the activation energy barrier (EA) and enter a higher excited state (or reach) via "path ②". 4 G 5 / 2(The region at the intersection with the charge transfer band CTB). Unlike the luminescence process at room temperature, these electrons that enter higher excited states no longer emit light through radiation, but instead rapidly relax back to the ground state through a non-radiative pathway (i.e., "process ③"). During this process, the energy of the electrons is transferred to the main lattice of the material in the form of heat and is eventually dissipated.

[0112] As the temperature rises further, the proportion of electrons choosing the aforementioned non-radiative relaxation pathways gradually increases, leading to a decrease in the number of electrons undergoing radiative transitions. This ultimately results in a decrease in the luminescence intensity of Sm³⁺ ions, and the material exhibits a significant thermal quenching phenomenon.

[0113] To further understand Sr 1.96 GaTaO6:4%Sm 3+ The thermal stability of the phosphor was evaluated using the Arrhenius equation: ∆E:

[0114]

[0115] Where I0 is the integral PL intensity at the initial temperature (300K), It is the integral PL intensity at the test temperature (350K-500K), A is a phosphor-related constant, ∆E is the activation energy of the sample, and K is the Boltzmann constant (8.167 × 10⁻⁶). -5 (eV / K). The Sr can be obtained from the above formula. 1.96 GaTaO6:4%Sm 3+ Phosphor Ln[(I0 / I t The relationship between )-1] and 1 / KT, such as Figure 4 As shown in (e), the linear fit between the two exhibits a good linear relationship, and the calculated Sr 1.96 GaTaO6:4%Sm 3 + The phosphor has a ∆E value of 0.211 eV, and its thermal quenching value is higher than that of other studies in the same field, such as Ca3Gd2Si3O. 12 :Sm 3+ (0.1608eV) and Ca2GaTaO6:Sm 3+ (0.098 eV), this finding indicates that Sr 1.96 GaTaO6:4%Sm 3+ Phosphors have excellent thermal stability and have great application potential in solid-state lighting technology.

[0116] Figure 4 (f) shows the Sr in the temperature range of 300K - 500K. 1.96 GaTaO6:4%Sm 3+The color coordinate changes clearly show that the phosphor's color coordinates only shift slightly with temperature changes, indicating that the phosphor has good color quality at high temperatures and can therefore be used as a NUV-excited WLED. As shown in Table 2, at temperatures of 300K-500K, the CCT color purity reaches as high as 90.37% in the range of 1710–1713 K. Therefore, it can play a prominent role as the red component of WLEDs.

[0117] Table 2 Sr 1.96 GaTaO6:4%Sm 3+ Color coordinates, CCT, and color purity changes within a temperature range of 300K - 500K

[0118]

[0119] 4. Optical temperature measurement performance analysis

[0120] pass Figure 5 (a) in the discovery of Sr 1.96 GaTaO6:4%Sm 3+ The main emission peak of the phosphor increases with temperature from 300K to 500K. 4 G 5 / 2 → 6 H 7 / 2 The characteristic transitions decrease monotonically, while Sm 3+ The center of gravity of the launch remained unchanged, still at [center]. 4 G 5 / 2 → 6 H 7 / 2 The transition is dominant. The emission intensity of the other three emission peaks did not decrease significantly. Therefore, it is speculated that Sr... 1.96 GaTaO6:4%Sm 3+ Phosphors have certain optical temperature measurement properties.

[0121] Temperature changes affect the emission parameters (including spectral shift, bandwidth, intensity, etc.) of the emission center. The thermal behavior of these parameters due to temperature changes influences spectral characteristics in a non-invasive or semi-invasive manner. Therefore, to avoid the influence of excitation source and detector errors, the relative change in the intensity ratio of two independent energy level transitions is selected as the research indicator. 4 G 5 / 2 → 6 H 7 / 2 and 4 G 5 / 2 → 6 H J The fluorescence intensity ratios corresponding to (J=5 / 2, 9 / 2, 11 / 2) can be fitted using the equation:

[0122]

[0123] Where A is a constant, B is the pre-exponential factor, ∆E is the activation energy, and K B Boltzmann constant (K) B =1.380649×10⁻²³ J / K), where T is the thermodynamic temperature. (This is achieved through...) Figure 5 (b) shows the fit to the FIR, and the coefficient of determination R after fitting is... 2 The value is 0.99, indicating a good fit. We can see... 4 G 5 / 2 → 6 H 7 / 2 and 4 G 5 / 2 → 6 H 5 / 2 The ratio is the largest, therefore these two transition peaks are the best choice for optical temperature measurement.

[0124] In addition, absolute sensitivity (S a ) and relative sensitivity (S r S is an important parameter for evaluating the optical temperature sensing performance of phosphors: a S represents the rate of change of fluorescence intensity ratio (FIR) with temperature. r This reflects the rate of change of fluorescence intensity ratio (FIR) in response to temperature changes. Both can be derived using formulas:

[0125]

[0126]

[0127] Figure 5 (c) and (d) in the figure show that S r and S a (correspond 4 G 5 / 2 → 6 H 7 / 2 and 4 G 5 / 2 → 6 H 5 / 2 The optimal sensitivity values ​​for the intensity ratio are 0.811%K. -1 and 0.341K -1 Therefore, it can be seen that Sr 1.96 GaTaO6:4%Sm 3+ Phosphors possess excellent optical temperature measurement performance and show great application potential in the field of optical temperature sensing.

[0128] 5. To investigate Sr 1.96 GaTaO6:4mol%Sm 3+The invention demonstrates the application value of commercial green phosphor (Ba2SiO4:Eu) in white light-emitting diodes. 2+ ), commercial blue phosphor BAM (BaMgAl) 10 O 17 Eu 2+ ) and Sr 1.96 GaTaO6:4%Sm 3+ They are mixed at a mass ratio of 1:1:800 and packaged together into an LED chip with an excitation wavelength of 410nm.

[0129] Under test conditions of 3V voltage and 300mA current, the appearance and color coordinates of the prepared WLED are as follows: Figure 6 As shown in (a), its chromaticity coordinates are (0.329, 0.332), which is close to the standard white light reference point; Figure 6 The illustration (a) further shows that the LED can emit bright warm white light when driven by a current of 300mA, and the correlated color temperature (CCT) reaches 5521K and the color rendering index (Ra) reaches 93.6, indicating that the WLED packaging effect is excellent.

[0130] Figure 6 (b) shows the electroluminescence (EL) spectrum of the prepared WLED. To investigate the effect of current on the performance of the WLED, the experiment further tested the electroluminescence spectroscopy (EL) spectrum in the range of 50–300 mA. The results show that: Figure 6 Sm is clearly presented in (b) of the text. 3+ Ion 4G 5 / 2 → 6 H J The four characteristic peaks of the (J=5 / 2, 7 / 2, 9 / 2, 11 / 2) transition; and the color rendering index R of WLED under different driving currents. a Its R value remained consistently between 90.6 and 93.6, ensuring high-quality color rendering performance. a For fluctuation information, please refer to Figure 6 The illustration in (b) above demonstrates that Sr 1.96 GaTaO6:4%Sm 3+ It possesses excellent optical performance in WLED.

[0131] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A Sm 3+ Sr2GaTaO6 phosphor doped with Ce, characterized in that, Chemical formula: Sr 2-x% GaTaO6: x%Sm 3+ wherein x is Sm 3+ doping molar amount, and 1≤x≤7.

2. The Sm of claim 1 3+ The Sr2GaTaO6 doped fluorescent powder is characterized in that, The x is 1, 2, 3, 4, 5, 6 or 7.

3. The Sm of claim 1 3+ The Sr2GaTaO6 doped fluorescent powder is characterized in that, The x is 4.

4. A Sm as claimed in any one of claims 1 to 3 3+ The application discloses a preparation method of a Sr2GaTaO6 fluorescent powder, and belongs to the technical field of luminescent materials. The method comprises the following steps: a. SrCO3, Ga2O3, Ta2O5, and Sm2O3 as raw materials, and the stoichiometric ratio of the chemical formula Sr 2-x% GaTaO6: x%Sm 3+ each raw material is weighed according to the stoichiometric ratio of the chemical formula Sr b. Mix and grind the weighed raw materials uniformly; c. The ground mixture is placed in a muffle furnace for high-temperature sintering to obtain the Sm 3+ Sr2GaTaO6 doped fluorescent powder.

5. The preparation method according to claim 4, characterized in that, The purity of the SrCO3, Ga2O3, Ta2O5 and Sm2O3 is 99.99%.

6. The preparation method according to claim 4, characterized in that, The grinding time is 30 minutes.

7. The preparation method according to claim 4, characterized in that, The specific operation steps of the high-temperature sintering are as follows: pre-sintering from room temperature to 600 DEG C and keeping for 2 hours, then final sintering by increasing the temperature to 1300 DEG C and keeping for 8 hours, natural cooling to room temperature after sintering is completed, and grinding the sintered product into powder.

8. A Sm as claimed in any one of claims 1 to 3 3+ Use of doped Sr2GaTaO6 phosphor in the preparation of white light emitting diodes.

9. A Sm as claimed in any one of claims 1 to 3 3+ Application of Sr2GaTaO6 phosphor doped with rare earth ions in optical temperature measurement.

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