A red luminescent fluorescent powder with excellent thermal stability and optical temperature sensor characteristics, and a preparation method and application thereof

Abstract

This invention provides a red luminescent phosphor with excellent thermal stability and optical temperature sensor properties, its preparation method, and its applications, belonging to the field of photoluminescent material preparation technology. The red luminescent phosphor, with the chemical formula Ca, is prepared by a high-temperature solid-state method. 2‑x Sm x AlNbO6, where x is Sm 3+ The molar ratio of doping is 0.01 ≤ x ≤ 0.06, with x preferably taking the value of 0.04. The red luminescent phosphor Ca of this invention... 2‑x Sm x AlNbO6 achieves high thermal stability for red light by relying on a double perovskite matrix, and also has excellent potential for light emission, temperature measurement and WLED applications, providing experimental and theoretical reference for the development of high thermal stability red phosphors.

Description

Technical Field

[0001] This invention belongs to the field of photoluminescent material preparation technology, and particularly relates to a red luminescent phosphor with excellent thermal stability and optical temperature sensor properties, its preparation method and application. Background Technology

[0002] White light-emitting diodes (WLEDs) have gained significant attention in modern lighting and optoelectronics due to their core advantages such as environmental friendliness, energy efficiency, long lifespan, high luminous efficiency, small size, low power consumption, and high stability, and have achieved widespread application. Phosphor-converted white light-emitting diodes (pc-WLEDs), as the mainstream technology, have further broadened their application scenarios thanks to their outstanding advantages such as high efficiency and instantaneous response. Inorganic fluorescent materials are the core component of pc-WLEDs, playing an irreplaceable key role in optimizing device performance. Currently, commercially available white LEDs generally use InGaN blue LED chips paired with YAG:Ce LEDs. 3+ The combination of yellow phosphors enables white light output. However, this technology system has an inherent defect of missing red components in the spectrum, which directly leads to a low color rendering index and a high correlated color temperature, making it unable to meet the stringent application requirements of high-quality lighting scenarios.

[0003] To address the shortcomings of existing commercial WLEDs, improving their color rendering index (CRI), color temperature, and color stability, expanding their color gamut coverage, and incorporating rare earth ions to prepare red phosphors to supplement the red light component of the spectrum are core technical pathways for enhancing the color rendering performance and color purity of WLEDs. However, in the field of red light-emitting materials, there is a significant negative correlation between emission wavelength and thermal stability. That is, the more the emission peak shifts towards longer-wavelength red light, the more exponentially more difficult it becomes to maintain high-temperature luminescence stability. Furthermore, traditional red phosphors (such as SrS2:Eu)... 2+ CaS:Eu 2+ Due to their low luminescence intensity, unstable chemical structure, and poor thermal stability, red phosphors are limited in practical applications, necessitating the development of novel, high-quality red fluorescent materials. Therefore, researching and developing red phosphors with high thermal stability for application in white light-emitting diode (wLED) technology has become a key research area in the field of light emission and has significant practical implications.

[0004] In the current research context, there is an urgent need to develop a red phosphor material with high thermal stability, high color purity, and high color rendering index, and to prepare it using a low-cost and time-efficient synthesis method to meet the application requirements of lighting technology. Among various rare-earth activating ions, Sm 3+ Ions possess complex and abundant energy level structures, characterized by... 4 G 5 / 2 → 6 H jEnergy level transitions of (J=5 / 2, 7 / 2, 9 / 2, 11 / 2) can emit bright orange-red fluorescence, making them preferred activating ions for preparing high-performance red luminescent phosphors. In recent years, various Sm... 3+ Doped fluorescent materials such as Sr3TaGa3Si2O 14 :Sm 3+ (See X. Li, Y. Zhong, T. Su, Y. Li, W. Wang, J. Xie, C. Wang, Y. Pan, 14 :Sm 3+ for opticalthermometry and white light emitting diodes, Journal of Molecular Structure, (2025), p. 144375.), Sr2YSbO6:Sm 3+ (See Y. Hua, ZJICC Li, Synthesis and photoluminescence properties of novel orange-emitting Sr2YSbO6:Sm 3+ phosphors for potential solid-state lighting, Inorganic Chemistry Communications, 128(2021), p. 108576.), Ca2LiScB4O 10 :Sm 3+ (See G. Sun, QJJ o. A. Chen, Compounds, Novel red-emitting Ca2LiScB4O 10 :Sm 3+Phosphorus for WLED: Photoluminescence, thermal stability, crystal structure, Judd-Ofelt parameters and energy band gap studies, Journal of Alloys and Compounds, 936(2023), p. 168263.) and other related research reports have been successively published, and some systems have shown considerable internal quantum efficiency and good thermal stability, possessing practical application potential. However, there are still shortcomings, such as insufficient development of double perovskite matrix systems, generally weak lattice rigidity making it difficult to synergistically improve red light thermal stability and high color purity, and existing Sm 3+ The single function of doped materials makes it difficult to simultaneously meet the integrated application requirements of high-quality white light illumination and high-precision optical temperature measurement.

[0005] It is evident that existing commercial white light-emitting diodes (LEDs) suffer from technical challenges such as the lack of red light components, poor color rendering, and poor thermal stability of red phosphors. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes a red luminescent phosphor with excellent thermal stability and optical temperature sensor properties, along with its preparation method and applications.

[0007] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a red luminescent phosphor with excellent thermal stability and optical temperature sensor properties, the chemical formula being Ca. 2-x Sm x AlNbO6, where x is Sm 3+ The molar ratio of doping is 0.01 ≤ x ≤ 0.06.

[0008] Double perovskite structure compounds (general molecular formula AA'BB'O6) possess excellent physical stability and chemical inertness. Their internal BO6 and B'O6 octahedral units are periodically alternating, allowing for precise control of lattice field strength and local symmetry. This provides a highly compatible lattice embedding environment for rare-earth doping ions, making them ideal luminescent matrix materials. Ca2AlNbO6, as a typical double perovskite structure niobate material, has a regular crystal structure and outstanding thermal stability, possessing excellent matrix conditions suitable for rare-earth ion doping and exhibiting high research and application value. Therefore, the red luminescent phosphor of this invention uses double perovskite structure Ca2AlNbO6 as the matrix, Sm... 3+ Ionic components occupy Ca 2+ Ionic lattice sites.

[0009] Furthermore, x can take values ​​of 0.01, 0.02, 0.03, 0.04, 0.05, or 0.06.

[0010] Furthermore, x is set to 0.04, and the chemical formula of the red luminescent phosphor is Ca. 1.96 Sm 0.04 AlNbO6.

[0011] This invention also provides a method for preparing the above-mentioned red luminescent phosphor with excellent thermal stability and optical temperature sensor properties, comprising the following steps: According to the chemical formula, CaCO3, Al2O3, Nb2O5 and Sm2O3 were weighed, and the raw materials were mixed and ground. After sintering, they were sintered by high temperature solid-state method. After sintering, the mixture was cooled to room temperature and ground into powder again to obtain the red luminescent phosphor with excellent thermal stability and optical temperature sensor characteristics.

[0012] Furthermore, the high-temperature solid-state method includes the steps of pre-sintering and sintering.

[0013] Furthermore, the pre-sintering temperature is 600°C and the time is 2 hours.

[0014] Furthermore, the sintering temperature is 1500°C and the time is 6 hours.

[0015] The present invention also provides an application of the above-mentioned red luminescent phosphor in the preparation of white light emitting diodes (WLEDs) or optical temperature sensors.

[0016] The present invention also provides a white light-emitting diode comprising the above-mentioned red light-emitting phosphor, as well as green phosphor and blue phosphor.

[0017] The present invention also provides an optical temperature sensor comprising the aforementioned red luminescent phosphor, wherein the sensor is based on the Sm content in the red luminescent phosphor. 3+ Ionic 4 G5 / 2→ 6 H9 / 2 and 4 G5 / 2→ 6 Temperature detection can be achieved by using the fluorescence intensity ratio of the H5 / 2 transition as a function of temperature.

[0018] Compared with the prior art, the present invention has the following advantages and technical effects: The red luminescent phosphor Ca of the present invention 2-x Sm x AlNbO6 uses Ca2AlNbO6 with a double perovskite structure as the matrix, Sm 3+ Ionic components occupy Ca 2+The Ca2AlNbO6 matrix, with its stable lattice environment and 3.7038 eV band gap, provides excellent thermal stability. Under 407 nm light excitation, the red phosphor of this invention exhibits strong red emission at 647 nm. 3+ The optimal doping concentration is 4 mol%, achieving a color purity of 96.32% and excellent color stability. Thermal stability tests show that, at 423 K, the red phosphor of this invention, with a high activation energy of 0.117 eV, maintains 94.09% of its room temperature luminescence intensity at 323 K and above 82.64% at 423 K, exhibiting outstanding resistance to thermal quenching among red phosphors. Its internal quantum efficiency reaches 27.03%, combining excellent luminescence and heat resistance. A white light-emitting diode was fabricated by packaging the optimal sample, resulting in a device with a color rendering index of 93.12 and a correlated color temperature of 5559.25 K, demonstrating excellent photoelectric performance. Simultaneously, the material possesses good optical temperature sensing characteristics, with Sr and Sa reaching 1.68% K. -1 and 0.0772K -1 .

[0019] In summary, the red luminescent phosphor Ca of the present invention 2-x Sm x AlNbO6 achieves high thermal stability for red light by relying on a double perovskite matrix, and also has excellent potential for light emission, temperature measurement and WLED applications, providing experimental and theoretical reference for the development of high thermal stability red phosphors. Attached Figure Description

[0020] 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: Figure 1 (a) shows the XRD patterns of the phosphors in Examples 1-6 and Comparative Example 1; (b) shows a schematic diagram of the three-dimensional crystal structure of Ca2AlNbO6 material; and (c) shows the Ca2AlNbO6:0%Sm 3+ Rietveld structure refinement and crystal structure, (d) is Ca2AlNbO6:4%Sm 3+ Rietveld structure refinement and crystal structure; Figure 2 The Ca2AlNbO6:4%Sm obtained in the example 3+ The samples were characterized by scanning electron microscopy (SEM) and energy dispersive spectroscopy, where (a) is Ca2AlNbO6:4%Sm 3+ Scanning electron microscope (SEM) images of the samples; (b)~(g) are Ca2AlNbO6:4%Sm 3+ Elemental distribution mapping of the sample; Figure 3 The composition is Ca2AlNbO6:4%Sm 3+ The energy dispersive spectroscopy (EDS) spectrum of the sample, with the left and right insets showing the atomic percentage (at%) and weight percentage (wt%), respectively; Figure 4 (a) shows the band structure and density of states distribution of Ca2AlNbO6, and (b) shows the total density of states (TDOS) and partial density of states (PDOS). Figure 5 (a) shows the Ca2AlNbO6:x%Sm obtained in Examples 1-6 at an emission wavelength of 647nm. 3+ The excitation spectrum of the material, (b) is the Ca2AlNbO6:x%Sm obtained in Examples 1-6 at an emission wavelength of 407 nm. 3+ The emission spectrum of the material, (c) is Ca2AlNbO6:x%Sm 3+ Sm in the material 3+ log(I / ) of ion concentration x ) and log( x (d) shows the linear relationship between ED and MD transitions and the emission intensity changes with concentration. Figure 6 (a) shows the Ca2AlNbO6:x%Sm obtained in Examples 1-6 under 407nm excitation. 3+ The evolution law of chromatic coordinates of materials, (b) is the CIE chromaticity coordinate distribution of phosphors under different doping concentrations; Figure 7 In the middle (a), Sm 3+ Ion energy level transition diagram, (b) is for Ca2AlNbO6:0.04Sm 3+ The IQE of the phosphor, (c) is Ca2AlNbO6:0.04Sm 3+ Fluorescence lifetime diagram of phosphor; Figure 8 In example (a), Ca2AlNbO6:0.04Sm is used. 3+ The trend of phosphor emission intensity with increasing temperature, (b) is the Ca2AlNbO6:0.04Sm in the example. 3+ The thermal stability contour plot of the phosphor, (c) shows the Ca2AlNbO6:0.04Sm in the example. 3+ The linear graph of the thermal stability of the phosphor, (d) is ln[(I0 / I T The schematic diagram of the relationship between )–1] and 1 / T shows that (e) represents Ca2AlNbO6:0.04Sm 3+ Thermal quenching mechanism of phosphors; Figure 9In the example, Ca2AlNbO6:0.04Sm 3+ The evolution of chromaticity coordinates of phosphors with temperature; Figure 10 (a) is 4 G 5 / 2 → 6 H J (J = 5 / 2, 9 / 2) The change in transition peak intensity with increasing temperature, (b) is 4 G 5 / 2 → 6 H 9 / 2 and 4 G 5 / 2 → 6 H 5 / 2 Light intensity ratio (FIR) fitting, (c) and (d) are S calculated at different temperatures. r and S a ; Figure 11 (a) shows the CIE coordinates and equal energy point of the fabricated white light emitting diode (WLED), the inset shows a photograph of the fabricated white light emitting diode, (b) shows the electroluminescence spectrum of the fabricated white light emitting diode (WLED) 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

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] This invention provides a red luminescent phosphor with excellent thermal stability and optical temperature sensor properties, the chemical formula of which is Ca. 2-x Sm x AlNbO6, where x is Sm 3+ The molar ratio of doping is 0.01 ≤ x ≤ 0.06.

[0027] In a preferred embodiment of the present invention, x takes the value of 0.01, 0.02, 0.03, 0.04, 0.05, or 0.06; more preferably, x takes the value of 0.04, and the chemical formula of the red luminescent phosphor is Ca. 1.96 Sm 0.04 AlNbO6.

[0028] This invention also provides a method for preparing the above-mentioned red luminescent phosphor with excellent thermal stability and optical temperature sensor properties, comprising the following steps: According to the chemical formula, CaCO3, Al2O3, Nb2O5 and Sm2O3 were weighed out, and the raw materials were mixed and ground. After sintering, they were sintered by high temperature solid-state method. After sintering, the mixture was cooled to room temperature and ground into powder again to obtain red luminescent phosphor with excellent thermal stability and optical temperature sensor characteristics.

[0029] In a preferred embodiment of the present invention, the high-temperature solid-state method includes the steps of pre-sintering and sintering, wherein the pre-sintering temperature is 600°C and the time is 2 hours, and the sintering temperature is 1500°C and the time is 6 hours.

[0030] More specifically, the preparation method of the red luminescent phosphor in this embodiment of the invention includes the following steps: According to the chemical formula (Ca) 2-x Sm xThe amount of each raw material was calculated using AlNbO6 (where x takes values ​​of 0.01, 0.02, 0.03, 0.04, 0.05, or 0.06). Then, CaCO3, Al2O3, Nb2O5, and Sm2O3 were accurately weighed using an electronic balance. All raw materials were placed in an agate mortar and ground thoroughly with alcohol for 30 minutes. The uniformly mixed raw materials were then placed in a muffle furnace for sintering. The temperature was first raised from room temperature to 600℃ for pre-sintering for 2 hours, then further increased to 1500℃ for sintering for 6 hours. Finally, after sintering, the sample was allowed to cool naturally to room temperature, removed, and ground again into powder to obtain the red luminescent phosphor. The specific reaction equation is as follows: .

[0031] The present invention also provides an application of the above-mentioned red luminescent phosphor in the preparation of white light emitting diodes (WLEDs) or optical temperature sensors.

[0032] The present invention also provides a white light-emitting diode, comprising the above-mentioned red light-emitting phosphor, as well as green phosphor and blue phosphor.

[0033] This invention also provides an optical temperature sensor comprising the aforementioned red luminescent phosphor, the sensor being based on the Sm content in the red luminescent phosphor. 3+ Ionic 4 G5 / 2→ 6 H9 / 2 and 4 G5 / 2→ 6 Temperature detection can be achieved by using the fluorescence intensity ratio of the H5 / 2 transition as a function of temperature.

[0034] All raw materials used in the embodiments of the present invention were commercially available, and the purity of CaCO3, Al2O3, Nb2O5 and Sm2O3 was 99.99%.

[0035] In this embodiment of the invention, room temperature refers to "25±2℃".

[0036] In this embodiment of the invention, a high-temperature solid-state method is used to prepare a red luminescent phosphor (chemical formula Ca). 2-x Sm x AlNbO6, also written as Ca2AlNbO6:xSm 3+ The study systematically characterized and deeply analyzed key performance indicators such as phase structure, microstructure, photoluminescence spectrum, thermal stability, and internal quantum efficiency of the sample, and screened out the doping ratio sample with the best luminescence performance. Subsequently, the optimal sample was packaged to prepare WLED devices, and the application potential of the red luminescent phosphor in the fields of white light illumination and optical temperature measurement was explored. This provides solid experimental data support and scientific theoretical reference for the research and development and practical application of novel multifunctional rare earth doped luminescent materials.

[0037] In the performance testing section of this invention, the samples were characterized by XRD using a Rigaku SmartLab SE X-ray diffractometer (Japan). A Cu-Kα radiation source (λ=1.5406Å) was used during the test, with a scanning angle range of 5°~90° and a scanning rate of 10°min. -1 The surface morphology and particle size of the samples were observed and analyzed using a Czech TESCAN MIRA LMS scanning electron microscope equipped with an Oxford energy dispersive spectrometer (EDS). The photoluminescence (PL) spectra of the samples were measured using a British Edinburgh FLS980 fluorescence spectrometer with an excitation source of Xe lamps and a spectral resolution of 0.2 nm.

[0038] For DFT first-principles calculations, a Ca2AlNbO6 crystal structure model was imported from a CIF file, and first-principles calculations were performed using DS-PAW software (Hongzhi Microelectronics Technology (Shanghai) Co., Ltd.). The calculations employed a density functional theory framework, using the projected augmented plane wave pseudopotential method (PAW) to describe the interaction between electrons and ion cores. The Perdew-Becke-Ernzerhof (PBE) functional under the generalized gradient approximation (GGA) was selected to handle the exchange correlation effects between electrons, and the unit cell structure was optimized. To ensure the accuracy of the wavefunction expansion, the plane wave cutoff energy was set to 500 eV. Then, the conjugate gradient method was used for structural relaxation, and the convergence criterion for electron energy iteration was set to less than 1 × 10⁻⁶. -6 The final electron energy is dE = -6.065 × 10⁻⁶ eV. -5 eV. The Brillouin zone k-point sampling adopts the Monkhorst-Pack central scheme and performs self-consistent calculations with a grid density of 5×5×3, achieving a balance between computational accuracy and efficiency, thereby obtaining a stable ground state configuration that can be used for subsequent electronic structure and optical performance analysis.

[0039] The technical solution of the present invention will be further illustrated by the following embodiments.

[0040] Examples 1-6 According to the chemical formula (Ca) 2-x Sm xAlNbO6 was used, where x took values ​​of 0.01 (Example 1), 0.02 (Example 2), 0.03 (Example 3), 0.04 (Example 4), 0.05 (Example 5), or 0.06 (Example 6). The amounts of each raw material were calculated, and CaCO3, Al2O3, Nb2O5, and Sm2O3 were accurately weighed using an electronic balance. All raw materials were placed in an agate mortar and ground thoroughly with alcohol for 30 minutes. The uniformly mixed raw materials were then placed in a muffle furnace for sintering. The temperature was first raised from room temperature to 600℃ for pre-sintering for 2 hours, then further raised to 1500℃ for sintering for 6 hours. Finally, after sintering, the samples were allowed to cool naturally to room temperature, removed, and ground again into powder to obtain different amounts of Sm2O3. 3+ Red phosphors with a doping molar ratio (exemplary, when x=0.04, the red phosphor Ca2AlNbO6:4%Sm is obtained) 3+ ).

[0041] Comparative Example 1 The amounts of each raw material were calculated according to the chemical formula (Ca2AlNbO6). Then, CaCO3, Al2O3, and Nb2O5 were accurately weighed using an electronic balance. All raw materials were placed in an agate mortar and ground thoroughly with alcohol for 30 minutes. The uniformly mixed raw materials were then placed in a muffle furnace for sintering. The temperature was first raised from room temperature to 600℃ for pre-sintering for 2 hours, then further increased to 1500℃ for sintering for 6 hours. Finally, after sintering, the sample was allowed to cool naturally to room temperature, removed, and ground again into powder to obtain Ca2AlNbO6 phosphor material with x = 0 (i.e., Ca2AlNbO6:0%Sm). 3+ ).

[0042] Performance test results (1) Synthesis and X-ray diffraction Figure 1 (a) shows the XRD patterns of the phosphors in Examples 1-6 and Comparative Example 1. The results indicate that the Ca2AlNbO6:xSm prepared in the examples... 3+ The main diffraction peaks of the series of phosphor samples basically match the main diffraction peak of Ca2AlNbO6 standard card number 97-017-2327, and the main peaks do not show obvious shifts, indicating that the phosphor based on Ca2AlNbO6 has been successfully synthesized. The phosphor obtained in the embodiments of the present invention is a typical double perovskite niobate with a cubic crystal structure corresponding to the space group P21 / n(14), and its lattice parameters are a=5.37858Å, b=5.419414Å, c=7.633447Å, α=γ=90°, β=89.969°, V=222.51Å. 3 Z=2.

[0043] Figure 1Image (b) shows a schematic diagram of the three-dimensional crystal structure of Ca2AlNbO6, which visually reflects its structural characteristics. Within the Ca2AlNbO6 crystal framework, Al... 3+ 、Nb 5+ Each of these atoms coordinates with six oxygen atoms, forming two octahedral structures: [AlO6] and [NbO6]. These two types of octahedrons are connected alternately by oxygen atoms at their vertices, forming a three-dimensional network structure. Ca... 2+ The ion is located in the interstitial space between the [AlO6] and [NbO6] octahedra, and it coordinates with the surrounding 8 atoms to form the [CaO8] polyhedron. Therefore, Sm can be calculated. 3+ The difference in ionic radius (Dr) between ions and other ions is used to determine Sm. 3+ The lattice site occupancy of ions in the Ca2AlNbO6 matrix is ​​calculated using the formula (1): ; In equation (1), CN Coordination number, Rp The matrix cation radius (Å) is... Rq Sm-doped 3+ Ionic radius (Å). Combining the similarity between ionic radius and valence state (Ca... 2+ The ionic radius is 1.23 Å ​​(coordination number CN = 6), Al 3+ The ionic radius of Nb is 0.535 Å (CN = 6). 5+ The ionic radius of Sm is 0.72 Å (CN = 6). 3+ The ionic radius is 0.958 Å (CN = 6). Calculations show Dr(Ca) = 22.12%, Dr(Al) = 79.07%, and Dr(Nb) = 33.06%. Therefore, Sm... 3+ More inclined to replace Ca 2+ This achieves unit point occupancy. Furthermore, to assess the stability of the perovskite structure of the matrix, the Goldschmidt tolerance factor (T) was used. f ) to make a judgment, when T f When the value is close to 1, it indicates that the double perovskite matrix has good structural stability, as shown in equation (2): ; in, R A For Ca 2+ Ionic radius (Å) R X For O 2- Ionic radius (Å) R M and R M’Al 3+ and Nb 5+ The ionic radius (Å) of Ca2AlNbO6 was calculated. f A value of 1.15 indicates that the matrix structure possesses double perovskite stability, providing an important structural basis for the material's high thermal stability. On one hand, its well-ordered crystal framework can resist lattice thermal vibrations at high temperatures, maintaining Sm... 3+ The stable coordination environment of the doped sites prevents the enhancement of nonradiative transitions caused by thermally induced lattice distortion. Furthermore, the intrinsic stability of the double perovskite structure suppresses the generation and proliferation of lattice defects at high temperatures, reducing energy dissipation channels, and simultaneously providing a suitable environment for Al atoms at the B sites of the double perovskite structure. 3+ The enhancement of lattice rigidity provides structural support, ultimately achieving a synergistic improvement in structural stability and lattice rigidity, thus endowing the material with excellent resistance to thermal quenching and thermal stability.

[0044] To further explore Sm 3+ The effect of doping on the lattice structure of materials was investigated using Jade software on Ca2AlNbO6:0%Sm 3+ and Ca2AlNbO6:4%Sm 3+ The sample underwent Rietvld refinement, and the results are as follows: Figure 1 As shown in (c) and (d), where (c) is Ca2AlNbO6:0%Sm 3+ Rietveld structure refinement and crystal structure, (d) is Ca2AlNbO6:4%Sm 3+ The Rietveld structure refinement and crystal structure are shown in the figure. Black dots represent experimental diffraction data, the red solid line represents the theoretical fitting curve, the green curve represents the deviation between the experimental and fitting data, and the short blue vertical line represents the theoretical Bragg diffraction peak positions corresponding to the standard PDF card. After refinement, the inconsistencies in the crystal structure parameters are 7.98% and 5.92%, respectively. The overall low inconsistencies indicate that the refinement results have high reliability.

[0045] (2) Study on appearance and morphology The Ca2AlNbO6:4%Sm obtained in the examples 3+ The samples were characterized by scanning electron microscopy (SEM) and energy dispersive spectroscopy, and the results are as follows: Figure 2 As shown, (a) is Ca2AlNbO6:4%Sm 3+ Scanning electron microscope (SEM) images of the samples; (b)~(g) are Ca2AlNbO6:4%Sm 3+ Elemental distribution mapping of the sample; Figure 3 Ca2AlNbO6:4%Sm 3+The energy dispersive spectroscopy (EDS) spectrum of the sample, with the left and right insets representing atomic percentage (at%) and weight percentage (wt%), respectively. According to... Figure 2 As can be seen in (a), Ca2AlNbO6:4%Sm 3+ The sample exhibits a certain degree of agglomeration, with irregular particle morphology and no fixed shape. The particle size is approximately 5 μm, exhibiting a micron-scale blocky structure. This microcrystalline characteristic is beneficial for enhancing the material's luminescent properties. According to... Figure 2 As can be seen from (b) to (g), the phosphor is composed of Ca, Al, Nb, O, and Sm atoms. All elements are uniformly distributed on the surface of the studied area, confirming the presence of Sm in the phosphor. Figure 3 The presence of characteristic peaks for Ca, Al, Nb, O, and Sm in the energy spectrum indicates that the target elements have been successfully introduced into the sample. The mass percentages of each element are Ca 29.25%, Al 8.01%, Nb 23.62%, O 33.98%, and Sm 5.13%, respectively, while the atomic percentages are Ca 21.22%, Al 8.63%, Nb 7.39%, O 61.76%, and Sm 0.99%, consistent with the theoretical stoichiometry. This further confirms the low Sm doping content of Ca₂AlNbO₆:4%Sm. 3+ The phosphor has been successfully synthesized. The results show that the prepared phosphor has the potential for application in white light-emitting diodes (LEDs) and solid-state display devices.

[0046] (3) Bandgap calculation Figure 4 (a) shows the band structure and density of states distribution of Ca2AlNbO6. Figure 4 (b) shows the total density of states (TDOS) and partial density of states (PDOS). The results indicate that the conduction band bottom (CBM) is mainly contributed by the s, p, and d orbitals of Nb atoms, with the d orbitals being dominant; the valence band top (VBM) is mainly contributed by the s and p orbitals of O atoms, with the p orbitals being dominant. Therefore, the intrinsic band gap transitions of Ca2AlNbO6 are mainly the transitions from the 2p state electrons of O to the 5d orbitals of Nb, corresponding to the O transitions during light absorption. 2- →Nb 5+ The leap. From Figure 4 As shown in Figure (a), the band structure reveals that both the valence band top (VBM) and conduction band bottom (CBM) are located at the Γ point, indicating that the crystal is a direct bandgap semiconductor with a theoretically calculated bandgap value of 3.7038 eV. The relatively wide bandgap is beneficial for suppressing nonradiative recombination, potentially endowing the material with higher quantum efficiency and promoting efficient energy utilization and conversion during luminescence. This electronic structure characteristic plays a crucial regulatory role in the material's luminescence behavior, providing a theoretical basis for a deeper understanding of its luminescence mechanism.

[0047] (4) Photoluminescence properties At room temperature, the Ca2AlNbO6:x%Sm obtained in Examples 1-6 was emitted at a wavelength of 647 nm. 3+ The materials (x = 0.01, 0.02, 0.03, 0.04, 0.05, or 0.06) were tested, and the resulting excitation spectra are shown in [reference needed]. Figure 5 In Figure (a), it can be seen that a set of sharp excitation peaks can be observed in the range of 350 nm to 500 nm, located at 365 nm, 379 nm, 407 nm, 420 nm, 442 nm, 468 nm, and 482 nm, respectively, corresponding to Sm 3+ A typical 4f-4f forbidden parity and spin transition. Its transition process is in the ground state ( 6 H 5 / 2 → Excited state ( 3 F 9 / 2 , 4 K 11 / 2 , 4 F 7 / 2 , 6 P 5 / 2 and 4 P 5 / 2 , 4 G 9 / 2 , 4 I 13 / 2 , 4 I 11 / 2 The highest excitation peak intensity was observed at 407 nm, indicating that light energy in the ultraviolet to blue-violet region effectively excites the phosphor, which matches the emission band of commercial white light WLEDs well and can be efficiently excited by the 405 nm UV InGaN chip in the WLED. Therefore, the Ca2AlNbO6:xSm prepared in the example... 3+ Phosphors have great application potential in the field of WLEDs.

[0048] At room temperature, the Ca2AlNbO6:x%Sm obtained in Examples 1-6 was emitted at a wavelength of 407 nm. 3+ Materials (0.01, 0.02, 0.03, 0.04, 0.05, or 0.06) were tested, and the resulting emission spectra (PL) are shown below. Figure 5 As shown in Figure (b), the sample exhibits four characteristic emission peaks at 566, 601, 647, and 711 nm, corresponding to Sm 3+ Ionic 4 G 5 / 2 → 6 H Z (Z = 5 / 2, 7 / 2, 9 / 2, 11 / 2) transitions. Under 407 nm excitation, the emission peak intensity is highest at 601 nm. Experimental results confirm that Ca2AlNbO6:xSm3 + The optimal doping concentration of the phosphor is approximately 4 mol%. Ca2AlNbO6:x%Sm 3+ The material's lg(I / x) and log( x The relationship between ) is seen Figure 5 From (c), it can be seen that as Sm 3+ When the doping concentration is increased to the optimal concentration, Sm 3+ Decreasing interionic spacing enhances energy transfer and increases emission intensity. Sm 3+ As the doping concentration increases further, due to the continued increase in Sm 3+ Concentration enhances the interaction between luminescent centers, increases the probability of nonradiative transitions, and decreases luminescence intensity, exhibiting concentration quenching (CQ) behavior. Based on Blasse's research, the CQ mechanism can be further analyzed using equation (3): ; In equation (3), R c The critical distance (Å) reflects the distance between the quenching ion and the activator ion. V It is the volume of a unit cell (Å) 3 ), x This is the optimal doping concentration for ions. N It is the number of sites available for doping in a unit cell. x Substituting =0.04, V=222.05Å and N=2 into the above formula, we can calculate that in Ca2AlNbO6:0.04Sm 3+ middle, R c The value is approximately 17.44 Å. There are three concentration quenching mechanisms: exchange interaction, radiative reabsorption interaction, and electric multipolar interaction. Generally, when Rc < 5 Å, exchange interaction is the main mechanism of concentration quenching; otherwise, non-radiative energy transfer is mainly due to electric multipolar interaction. However, the calculated result is much greater than 5 Å, suggesting that in Ca2AlNbO6:0.04Sm... 3+ The mechanism of quenching at medium concentrations is dominated by electro-multilevel interactions.

[0049] To further investigate Sm in the Ca2AlNbO6 matrix 3+ The energy transfer (ET) mechanism between ions, based on the Dexter and Schulman models, relates luminescence intensity (I) to Sm. 3+ Doping concentration ( x The relationship between ) is calculated, as shown in equation (4): ; In the formula, x Sm3+ It refers to the concentration of ion doping.I It is the relative intensity of the emission peak. Q These are parameters for a specific type of electric multipole interaction. A These are the fitting parameters. Among them, Q =6, 8, and 10 represent dipole-dipole (dd), dipole-tetrapole (dq), and tetrapole-tetrapole (qq) interactions, respectively. Figure 5 (c) represents Sm 3+ log(I / ) of ion concentration x ) and log( x The linear relationship graph of the fitted curve, where Ri is the linear relationship of the fitted curve. 2 The value is 0.98, the slope is -3.42272, corresponding to -Q / 3, thus calculating Q=10.27, which is very close to the theoretical value of 10 for the quadrupole-quadrupole (qq) interaction. The results show that Sm 3+ The red emission quenching mechanism of Ca2AlNbO6 phosphor is mainly caused by nonradiative energy transfer due to quadrupole-quadrupole interactions, while energy transfer between ions is mainly due to long-range Coulomb interactions.

[0050] To determine Sm in the Ca2AlNbO6 matrix 3+ The characteristic energy level transition types of ions, this invention is based on the Judd-Ofelt (JO) theory, combined with the 4f transitions of rare earth ions. N The selection rules for intra-configuration transitions are analyzed. Electric dipole (ED) transitions are intrinsically parity forbidden. In rare-earth ions, forced ED transitions induced by non-centrosymmetric crystal fields are the main transition form. For f-electrons, the difference in the total angular quantum number J before and after the transition satisfies |ΔJ|≤6. When ΔJ=2, 4, or 6 and J or J'=0, the ED transition is forbidden. Magnetic dipole (MD) transitions are not subject to parity forbidden constraints, but are less sensitive to the symmetry of the local environment. The selection rule is |ΔJ|≤1, and transitions with J or J'=0 are strictly forbidden. Based on the above selection rules, the transition at 647 nm can be determined. 4 G 5 / 2 → 6 H 9 / 2 The transition (ΔJ=2) is an electric dipole (ED) transition (high intensity), at 566 nm. 4 G 5 / 2 → 6 H 5 / 2 The transition (ΔJ=0) is a magnetic dipole (MD) transition (moderate intensity), at 601 nm. 4 G 5 / 2 → 6 H 7 / 2 The transition (ΔJ=1) is an electric dipole / magnetic dipole hybrid (ED / MD) transition (low intensity).

[0051] It is worth noting that Sm 3+ Ion ED transition ( 4 G 5 / 2 → 6 H 9 / 2 The emission band strength of ) is higher than that of the MD transition ( 4 G 5 / 2 → 6 H 5 / 2 Its emitted light is orange-red, a phenomenon indicating that Sm 3+ The lattice sites occupied by ions in the Ca2AlNbO6 crystal lattice exhibit asymmetry. In this symmetry-broken environment, normally forbidden energy level transitions can be partially or completely unforbidden, thus significantly modulating the material's luminescence behavior. To characterize Sm... 3+ Based on the symmetry of the local environment in the matrix lattice, and according to the corollary of Judd-Ofelt theory, the intensity ratio of ED to MD transitions is defined as the asymmetry ratio (R), and its calculation formula is shown in equation (5): ; The results of the emission intensity changes of ED and MD transitions with varying concentrations are shown in the figure. Figure 5 In the middle (d), R>1 was observed at all different concentrations. When R>1, it indicates that Sm 3+ The ions occupy non-centrosymmetric positions in the Ca₂AlNbO₆ lattice. 3+ The highly asymmetric local environment surrounding ions facilitates the preparation of high-purity fluorescent materials; a larger R value indicates stronger Sm... 3+ The higher the degree of symmetry distortion of the lattice site, the greater the deviation from the inversion symmetry, the stronger the proportion of forced ED transitions, and the better the luminescence effect of the system.

[0052] Ca2AlNbO6:x%Sm obtained in Examples 1-6 under 407nm excitation 3+ The evolution of chromatic coordinates for materials (x = 0.01, 0.02, 0.03, 0.04, 0.05, or 0.06) is shown in [reference needed]. Figure 6 (a) The results show that the chromaticity coordinates of each phosphor only shift slightly with the change of test temperature, and the CIE chromaticity coordinate distribution of different samples is highly concentrated.

[0053] Figure 6 (b) shows the CIE chromaticity coordinate distribution of the phosphor at different doping concentrations, which intuitively reflects the Ca... 2- x Sm x The color of AlNbO6 varies with doping concentration. Specifically, Ca2AlNbO6:0.04Sm 3+The color coordinates are closer to the red region, indicating that phosphors with this doping concentration have potential application value in orange-red WLED emission.

[0054] Furthermore, color temperature and color purity are also key indicators for evaluating the color quality of luminescent materials. Therefore, this invention uses the McCamy equation to calculate the correlated color temperature (CCT) of the sample, the expressions of which are shown in equations (6) and (7): ; in, x , y The composition is Ca2AlNbO6:0.04Sm 3+ The CIE chromaticity coordinates are used to further characterize Ca2AlNbO6:0.04Sm. 3+ The color performance is calculated using equation (8) to determine color purity: ; In the formula, ( x i , y i ), ( x w , y w )and( x z , y z ) These represent the color coordinates of the sample, the coordinates of the standard white light source (0.333, 0.333), and the color coordinates corresponding to the dominant wavelength, respectively. Table 1 lists the color coordinates of different concentrations of Sm. 3+ CIE coordinates, CCT, and color purity of Ca2AlNbO6 phosphor at different doping concentrations. Calculations show that the color temperature distribution is in the range of 1743–1776 K, when Sm 3+ When the doping concentration is 4 mol%, the color purity of the sample can reach 96.32%, indicating that Sm 3+ Activated Ca2AlNbO6 phosphor exhibits excellent color purity.

[0055] Table 1. Different concentrations of Sm 3+ CIE coordinates, CCT and color purity of Ca2AlNbO6 phosphor at different doping concentrations Figure 7 In the middle (a), Sm 3+ The ion energy level transition diagram shows that Sm 3+ When ions are incorporated into the crystal lattice, their 4f electronic configuration undergoes energy level splitting under the influence of the crystal field, forming a series of discrete energy levels. When the energy of the incident photon matches the transition energy difference between specific energy levels, Sm... 3+The absorption of photons via the ff transition excites electrons from the ground state to a higher excited state, completing the light absorption process.

[0056] Because electrons in high-energy excited states are less stable, they relax rapidly to lower energy levels via nonradiative transitions (NR), eventually settling in the lowest excited state. 4 G 5 / 2 (Energy approximately 17500~18000 cm) -1 ).when 4 G 5 / 2 When electrons accumulate to a certain concentration at an energy level, they will emit photons via radiative transitions, transitioning to a higher energy level. 6 H J The energy levels (J=5 / 2, 7 / 2, 9 / 2, 11 / 2) and other lower energy levels eventually return to the ground state.

[0057] Internal quantum efficiency (IQE) is a core parameter for measuring the photoelectric conversion capability of optoelectronic devices, and it can effectively reflect the practical application potential of phosphors in lighting devices. The formula for calculating internal quantum efficiency is shown in equation (9): ; in, η It is the internal quantum efficiency (IQE) value. L S The composition is Ca2AlNbO6:0.04Sm 3+ Emission spectrum of phosphor, E R The excitation spectrum of the reference sample BaSO4 (BSO) is shown. E S The excitation spectrum of the sample to be tested is shown. Ca2AlNbO6:0.04Sm 3+ See IQE for phosphors Figure 7 In Figure (b), it can be seen that under the excitation condition of 407 nm, Ca2AlNbO6:0.04Sm 3+ The phosphor's IQE was calculated to be approximately 27.03%, although this value is only slightly higher than some other Sm 3+ Fluorescent materials with doped systems, such as NaSrLa(MoO4)O3:0.04Sm 3+ (21.32%) (see J. Xue, M. Song, HM Noh, SH Park, BR Lee, JHKim, JHJJ o. A. Jeong, Compounds, Near-ultraviolet light induced redemission in Sm 3+-activated NaSrLa (MoO4) O3phosphors for solid-state illumination, Journal of Alloys and Compounds, 817 (2020), p. 152705.), Ca2GdGa3Ge2O 12 0.04Sm 3+ (22.52%) (See H. Song, JJCI Li, A novel inorganic host matrix for Sm 3+ doping targeting at the achievement of high colorrendering WLEDs, Ceramics International, 51 15 (2025), p. 20709-20715.) and Li2NaBP2O8:0.02Sm 3+ (25.3%) (See J. Xiang, M. Yang, Y. Che, J. Zhu, Y. Mao, K. Xiong, HJCI Zhao, Photoluminescence investigation of novel reddish-orange phosphor Li2NaBP2O8: Sm 3+ (with high CP and low CCT, Ceramics International, 45 6 (2019), p. 7018-7024.), but it can be further improved by optimizing the experimental process.

[0058] Figure 7 In the middle (c), Ca2AlNbO6:0.04Sm is used. 3+ The fluorescence lifetime plot of the phosphor shows that its kinetics exhibit a typical decay pattern of initial rapid decline followed by a slow, steady stabilization. Given Sm... 3+ With only one emission center, the fluorescence decay curve can be fitted using a double exponential decay model, and its decay behavior can be accurately described by equation (10): ; In equation (10), I t For the sample in t The intensity of decay at any given moment, A 1 , A 2For the corresponding fitting constant, t For measurement time (ms), τ 1 , τ 2 These represent the short-lived and long-lived components, respectively, exhibiting degradation. Through fitting calculations, the following equation is obtained: Ca2AlNbO6:0.04Sm 3 + The decay time is 0.792 ms. This short fluorescence lifetime characteristic makes this fluorescent material well-suited for use in WLED devices.

[0059] (5) Thermal stability In practical operation, the chip temperature of WLEDs is typically higher than the ambient temperature. Long-wavelength red light materials have smaller emission energy level differences, and the lattice vibrations (phonon scattering) induced by temperature increases are more likely to trigger nonradiative recombination transitions, significantly exacerbating the thermal quenching effect. Simultaneously, long-wavelength red light materials often require redshifting through composition control, defect introduction, or narrow bandgap design, which further weakens lattice rigidity and enhances electron-phonon coupling, ultimately leading to a sharp decline in thermal stability. As temperature increases, the amplitude of lattice vibrations increases, the probability of nonradiative transitions increases, and the photoluminescence intensity of phosphors typically decreases, while the photoluminescence peak shifts. This undoubtedly hinders practical applications; therefore, a systematic evaluation of the thermal stability of phosphors is of great significance.

[0060] In the example, Ca2AlNbO6:0.04Sm 3+ The trend of phosphor emission intensity changing with increasing temperature is shown in the figure. Figure 8 As can be seen in (a), under 407 nm excitation, when the test temperature is gradually increased from 298 K to 473 K, the effect on Ca2AlNbO6:0.04Sm 3+ The emission spectra of the phosphor were continuously acquired. The results showed that the intensity of the characteristic emission peak at 601 nm exhibited good stability with increasing temperature, and the peak shape and energy level distribution of each emission peak did not change significantly. Meanwhile, when the temperature increased from 298 K to 473 K, the emission intensity of Ca2AlNbO6:0.04Sm... 3+ The main emission peak of the phosphor 4 G 5 / 2 → 6 H 9 / 2 The intensity of the characteristic transition also decreases monotonically with temperature, but its emission center of gravity does not shift and remains at the same level. 4 G 5 / 2 → 6 H 9 / 2 The transition is dominant. The intensity of the other three emission peaks does not decrease significantly with increasing temperature. Based on these results, it is inferred that Ca2AlNbO6:0.04Sm 3+Phosphors have certain potential for optical temperature sensing.

[0061] In the example, Ca2AlNbO6:0.04Sm 3+ The thermal stability contour plot of the phosphor is shown below. Figure 8 As shown in (b), the luminescence intensity decreases only slightly with increasing temperature. This is because the increased temperature leads to a higher probability of nonradiative transitions, which in turn causes a slight decrease in fluorescence emission intensity.

[0062] In the example, Ca2AlNbO6:0.04Sm 3+ The linear graph of the thermal stability of the phosphor is shown below. Figure 8 As shown in (c), this structure further confirms the Ca2AlNbO6:0.04Sm 3+ Phosphors possess excellent thermal stability. Improving the thermal stability of red-light phosphors is a key technical challenge in this field. Emission wavelength and thermal stability are negatively correlated, and improving the thermal stability of long-wavelength red light (around 650nm) is a recognized difficulty. Phosphors are considered to have thermal stability only when the thermal quenching effect is minimized and the thermal stability temperature T50 ≥ 423K. The characteristic temperature (T0.5) is usually defined as the temperature at which the luminescence intensity drops to 50% of room temperature.

[0063] Table 2 lists the thermal stability properties of existing phosphors. It can be seen that the thermal stability of reported red phosphors is generally poor, with luminescence intensity at 423 K mostly between 50% and 79%, even for Y₂O₃:Eu 3+ (480K, @50.04%) and YAG:Ce 3+ Commercial red phosphors such as (480K, @51.25%) also struggle to overcome this bottleneck, and similar Sm... 3+ The performance of doped red phosphors was also poor, and each material had inherent structural and mechanism-related defects, such as monoclinic Ca2GdNbO6:Sm 3+ Due to its low lattice symmetry and high distortion, Gd 3+ Radius greater than Al 3+ This leads to enhanced flexibility of the [GdO6] octahedron and large lattice vibration amplitude at high temperatures, resulting in Sm 3+ Due to local environmental imbalance, the luminescence intensity at 423K is only 65.32% of that at room temperature. (Hexagonal Sr2CaLa(VO4)3:Sm) 3+ With a [VO4] tetrahedral framework, the VO bonds have weak covalentity, resulting in high lattice flexibility and numerous grain boundary defects. At high temperatures, the functional groups are prone to vibrational distortion, leading to decreased energy transfer efficiency. At 423 K, the luminescence intensity is only 60.37% of that at room temperature. (Dual perovskite Ca2LaSbO6:Sm) 3+ Although it belongs to the same double perovskite structure as the material of this invention, Sb5+ [SbO6] octahedrons have large ionic radii, high polarizability, and weak lattice rigidity, making them prone to distortion at high temperatures. This leads to enhanced electron-phonon coupling and a low thermal activation energy, resulting in a luminescence intensity of only 53.8% of that at room temperature at 420 K. In contrast, the Ca2AlNbO6:0.04Sm prepared in this embodiment of the invention... 3+ Red phosphors rely on Al-based high-rigidity double perovskite structures, Al 3+ With O 2- Strong covalent bonds are formed between [AlO6] and [NbO6] octahedrons, exhibiting almost no distortion at high temperatures, effectively suppressing thermoluminescence decay. At 323K, the phosphor intensity remains 94.09% of its room-temperature intensity, and even at 473K, its luminescence intensity remains above 80% of its room-temperature level. 0.5 The K value is significantly higher than 500K, demonstrating performance that is considerably superior to other reported red phosphor materials of the same type. This indicates that the phosphor exhibits excellent stability under the high-temperature conditions of actual LED operation, showcasing its potential value as a red light component in WLED applications.

[0064] Table 2 Comparison of thermal stability properties of phosphors To further investigate Ca2AlNbO6:0.04 Sm 3+ The thermal stability of phosphors was assessed using the Arrhenius equation (Equation (11)). ∆E Perform quantitative calculations: ; in I 0 It is the integral intensity of PL at the initial temperature (300K). I t It is the PL integral intensity under test temperature (350K-500K). A It is a constant related to the sample. ∆E It is the activation energy of the phosphor. K It is the Boltzmann constant (8.167 × 10⁻⁶). -5 eV / K). Based on the above formula, a linear fit is performed on the data, ln[(I0 / I T The diagram illustrating the relationship between )–1] and 1 / T is shown below. Figure 8 As shown in (d), it can be seen that Ln[(I0 / I t [-1] shows a good linear correlation with 1 / KT. Calculations show that Ca2AlNbO6:0.04 Sm 3+The activation energy ∆E of the phosphor can reach 0.117 eV, slightly higher than that of other studies by peers, such as GGAG:0.05Cr. 3+ (0.078 eV) and Ca2GaTaO6:Sm 3 + (0.098 eV), the above results fully demonstrate that Ca2AlNbO6:0.04Sm 3+ Phosphors possess excellent resistance to thermal quenching and have promising application prospects in the field of solid-state lighting.

[0065] Ca2AlNbO6:0.04Sm 3+ The luminescence behavior and thermal quenching mechanism of phosphors can be reasonably explained using a configurational coordinate model, which plots ionic geometry on the x-axis and system energy on the y-axis. (Ca2AlNbO6:0.04Sm) 3+ The thermal quenching mechanism of phosphors is shown in Figure 8 In (e), under normal temperature conditions, when the material is excited by 407 nm light, Sm 3+ Ionic ground state 6 H 5 / 2 Electrons on the electron absorb photon energy and transition to an excited state. 4 F 7 / 2 Subsequently, the excited-state electrons relax to a metastable state via a nonradiative transition (NR). 4 G 5 / 2 Ultimately, the electron releases energy and emits visible light of different wavelengths through radiative transition (process ①), returns to the ground state, and completes the entire light emission process.

[0066] When the ambient temperature rises, the internal energy absorbed by the material exceeds its activation energy, and it enters a state of equilibrium. 4 G 5 / 2 Some electrons in the metastable state gain enough energy to overcome the activation barrier (E). A ), and transition along path ② to a higher excited state or reach 4 G 5 / 2 At the intersection with the charge transfer band (CTB), the number of phonons (lattice vibrations) in the material increases, and the enhanced electron-phonon interaction triggers a nonradiative transition. Finally, through process ③, the material returns to the ground state without emitting photons, and its energy is transferred to the lattice as heat and dissipated.

[0067] As temperature continues to rise, the proportion of electrons relaxing via non-radiative pathways increases, while the number of electrons participating in radiative transitions decreases accordingly, ultimately leading to Sm 3+ The luminescence intensity decreases, and since the luminescence intensity is inversely proportional to the temperature, the material exhibits typical thermal quenching behavior.

[0068] Figure 9 The composition is Ca2AlNbO6:0.04Sm 3+The evolution of chromatic coordinates with temperature shows that the chromatic coordinates of the sample only shift slightly with changes in test temperature, indicating that the phosphor can maintain stable luminous chromaticity even at high temperatures, demonstrating its potential as a near-ultraviolet-excited white LED material. As shown in Table 3, within the range of 298-473K, the correlated color temperature of the sample remains stable between 1733–1794K, with a color purity reaching 96.85%, far exceeding that of various previously reported Sm... 3+ Doped fluorescent systems, such as SrNb2O6:0.03Sm 3+ (88.19%), KBaScSi3O9:0.06Sm 3+ (86.9%), Ca3Al3N5:0.03Sm 3+ (52.56%), NaSrLa(MoO4)O3:0.04Sm 3+ (23.12%) and Li2NaBP2O8:0.03Sm 3+ (25.3%), which indicates that the phosphor has good color quality at high temperatures and still has excellent color purity and color stability at high temperatures, and can play an important role as an efficient red light-emitting component in WLED devices.

[0069] Table 3 Ca2AlNbO6:0.04Sm 3+ Changes in chromatic coordinates, CCT, and color purity within a temperature range of 300K-500K (6) Optical temperature sensing performance Figure 10 (a) is 4 G 5 / 2 → 6 H J (J = 5 / 2, 9 / 2) The change in transition peak intensity with increasing temperature, (b) is 4 G 5 / 2 → 6 H 9 / 2 and 4 G 5 / 2 → 6 H 5 / 2 Light intensity ratio (FIR) fitting, (c) and (d) are S calculated at different temperatures. r and S a .from Figure 10 (a) Discovery 4 G 5 / 2 → 6 H 9 / 2 The characteristic transition intensity decays the fastest, while 4 G 5 / 2 → 6 H 5 / 2The transition strength remains almost unchanged, and Figure 8 The consistency shown in (a) demonstrates the Ca2AlNbO6:0.04 Sm 3+ Potential for use in optical temperature measurement systems.

[0070] Temperature changes can modulate various luminescence parameters at the emission center, including spectral peak shifts, changes in spectral bandwidth, and attenuation of luminescence intensity. The thermal response behavior of these parameters with temperature changes alters the spectral characteristics of the material in a non-invasive or semi-invasive manner. Therefore, to effectively eliminate interference from excitation source fluctuations and detector errors, this invention selects the luminescence intensity ratio of two independent energy level transitions as the core research indicator. 4 G 5 / 2 → 6 H 9 / 2 and 4 G 5 / 2 → 6 H 5 / 2 The corresponding fluorescence intensity ratio (FIR) was used for fitting analysis, and the fitting equation is shown in equation (12): ; in, A It is a constant. B Δ is the pre-exponential factor. E For activation energy, K B Boltzmann constant (K) B =1.380649×10-23J / K), T This is the thermodynamic temperature. Based on... Figure 10 (b) The fluorescence intensity ratio was fitted and the resulting coefficient of determination R was calculated. 2 =0.99, indicating that the fitting result fits the experimental data very well. Because 4 G 5 / 2 → 6 H 9 / 2 and 4 G 5 / 2 → 6 H 5 / 2 The intensity ratio is the largest, therefore selecting this group of transition peaks as the characteristic peaks for optical thermometry is the optimal choice.

[0071] In addition, absolute sensitivity (Sa) and relative sensitivity (Sr) are important parameters for evaluating the optical temperature sensing performance of phosphors: Sa is the rate of change of fluorescence intensity ratio (FIR) with temperature, and Sr reflects the rate of change of fluorescence intensity ratio (FIR) in response to temperature changes. The calculation formulas are shown in equations (13) and (14). ; Figure 10The test results in (c) and (d) show that, with (corresponding to) 4 G 5 / 2 → 6 H 9 / 2 and 4 G 5 / 2 → 6 H 5 / 2 When the transition intensity ratio (the ratio of the intensities) is used as the basis for calculation, the optimal values ​​of Sr and Sa for this phosphor can reach 1.68% K. -1 and 0.0772 K -1 Table 4 shows the Sa and Sr values ​​and temperature ranges of various reported rare-earth ion-doped temperature sensing materials. The results indicate that this phosphor exhibits excellent performance in both relative sensitivity and temperature range. The above data fully demonstrate that Ca2AlNbO6:0.04 Sm 3 + Phosphors possess excellent optical temperature sensing performance, and have extremely high practical application value and broad development prospects in the field of optical temperature measurement.

[0072] Table 4. Comparison of Sa, Sr values ​​and temperature ranges of various reported rare-earth ion-doped temperature sensing materials. (7) WLEDs Applications The Ca2AlNbO6:0.04Sm obtained in the exploratory example 3+ The feasibility of practical application of phosphors in white light emitting diodes (WLEDs), using Ca2AlNbO6:0.04Sm 3+ Compared with commercial green phosphor (BaSiO4∶Eu) 2+ ), commercial blue phosphor BAM (BaMgAl) 10 O 17 Eu 2+ The powder was uniformly mixed at a mass ratio of 1:1:800, and the mixed powder was encapsulated in an LED chip with an excitation wavelength of 410nm to prepare a WLED device and conduct photoelectric performance testing.

[0073] Under test conditions of 3V operating voltage and 300mA drive current, Figure 11 Image (a) shows the CIE coordinates and equal energy point of the fabricated white light-emitting diode (WLED). The inset is a photograph of the fabricated WLED, with chromaticity coordinates of (0.331, 0.339), which closely approximates the standard white light reference point (0.333, 0.333), reflecting its excellent color purity and color rendering effect. Figure 11 As can be directly observed in the inset of (a), the device can emit bright warm white light when driven by a current of 300mA. Its correlated color temperature (CCT) is 5559.25K and its color rendering index (Ra) reaches 93.12. The excellent performance of various photoelectric parameters fully demonstrates that the phosphor can achieve good device fabrication results when applied to WLED packaging.

[0074] Figure 11 (b) shows the electroluminescence spectra of the fabricated white light-emitting diode (WLED) under different current driving conditions. The inset shows the variation of the Ra value of the WLED under different current driving conditions. The electroluminescence (EL) spectra of the device were measured every 100 mA within the current range of 100–400 mA. Sm can be clearly observed in the spectra. 3+ ion 4 G5 / 2→ 6 The four characteristic peaks of the HJ (J=5 / 2, 7 / 2, 9 / 2, 11 / 2) energy level transitions are observed. Furthermore, under different driving currents, the color rendering index Ra of this WLED device remains stable within the range of 92.4–94.6, demonstrating stable high-quality color rendering capability over a wide driving current range. The specific fluctuation pattern of its Ra value with current can be found in [reference needed]. Figure 11 Illustration (b) in the middle.

[0075] The above test results fully confirm that the Ca2AlNbO6:0.04Sm obtained in the example is effective. 3+ Phosphors exhibit excellent optical properties when applied to WLED devices, and are a high-quality red emitting material suitable for the fabrication of white light-emitting diodes.

[0076] In summary, this invention successfully prepared Ca using a high-temperature solid-state method. 2-x Sm x A novel AlNbO6 series of phosphors was systematically investigated, exploring their crystal structure, luminescent properties, and practical application potential. XRD and SEM measurements confirmed the presence of Sm+ doping. 3+ The crystal structure of Ca2AlNbO6 remained unchanged, and its band gap was calculated to be 3.7038 eV using first-principles calculations. The synthesized pure-phase Ca... 2-x Sm x AlNbO6 phosphor, when excited at 407 nm, exhibited four independent emission peaks at 566, 601, 647, and 711 nm, corresponding to Sm 3+ Ionic 4 G 5 / 2 → 6 H Z (Z=5 / 2, 7 / 2, 9 / 2, 11 / 2) transition, optimal Sm 3+The doping concentration is 4 mol%, and the red emission concentration quenching mechanism of this material is dominated by nonradiative energy transfer induced by quadrupole-quadrupole interactions. Ca 2-x Sm x AlNbO6 phosphor exhibits excellent thermal stability. Its 647nm red emission peak retains 94.09% of its room-temperature intensity at 323K and 82.64% at 423K, with an internal quantum efficiency of 27.03%, far superior to many previously reported red phosphor materials. Furthermore, the optimal doped sample achieves a correlated color temperature of 1793.35K and a color purity of 96.85%, demonstrating excellent color temperature stability. Its optical thermometric performance is also outstanding, with optimal relative sensitivity (Sr) and absolute sensitivity (Sa) reaching 1.68%K. -1 and 0.0772K -1 In addition, Ca2AlNbO6:0.04Sm 3+ A WLED device was fabricated using encapsulation. At a driving current of 300mA, the device exhibited a color rendering index (CRI) of 93.12 and a correlated color temperature (CCT) of 5559K, demonstrating excellent photoelectric performance. The results indicate that the Ca obtained in this invention... 2-x Sm x AlNbO6 phosphor combines excellent luminescent properties, outstanding red light thermal stability, superior optical temperature measurement capabilities, and potential for WLED packaging applications. It is a novel multifunctional luminescent material with broad application prospects in both optical temperature measurement and WLED fields.

[0077] 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.

Claims

1. A red luminescent phosphor with excellent thermal stability and optical temperature sensor properties, characterized in that, The chemical formula is Ca 2-x Sm x AlNbO6, where x is Sm 3+ The molar ratio of doping is 0.01 ≤ x ≤ 0.

06.

2. The red luminescent phosphor with excellent thermal stability and optical temperature sensor properties according to claim 1, characterized in that, x can take the values ​​0.01, 0.02, 0.03, 0.04, 0.05 or 0.

06.

3. The red luminescent phosphor with excellent thermal stability and optical temperature sensor properties according to claim 2, characterized in that, x is 0.04, and the chemical formula of the red luminescent phosphor is Ca. 1.96 Sm 0.04 AlNbO6.

4. A method for preparing a red luminescent phosphor with excellent thermal stability and optical temperature sensor properties as described in any one of claims 1 to 3, characterized in that, Includes the following steps: According to the chemical formula, CaCO3, Al2O3, Nb2O5 and Sm2O3 were weighed, and the raw materials were mixed and ground. After sintering, they were sintered by high temperature solid-state method. After sintering, the mixture was cooled to room temperature and ground into powder again to obtain the red luminescent phosphor with excellent thermal stability and optical temperature sensor characteristics.

5. The method for preparing the red luminescent phosphor with excellent thermal stability and optical temperature sensor properties according to claim 4, characterized in that, The high-temperature solid-state method includes the steps of pre-sintering and sintering.

6. The method for preparing the red luminescent phosphor with excellent thermal stability and optical temperature sensor properties according to claim 5, characterized in that, The pre-sintering temperature is 600℃ and the time is 2 hours.

7. The method for preparing the red luminescent phosphor with excellent thermal stability and optical temperature sensor properties according to claim 5, characterized in that, The sintering temperature was 1500℃ and the time was 6 hours.

8. The use of the red luminescent phosphor according to any one of claims 1 to 3 in the preparation of white light emitting diodes or optical temperature sensors.

9. A white light-emitting diode, characterized in that, It includes the red phosphor as described in any one of claims 1 to 3, as well as green and blue phosphors.

10. An optical temperature sensor, characterized in that, The sensor comprises the red luminescent phosphor according to any one of claims 1 to 3, and is based on the Sm content in the red luminescent phosphor. 3+ Ionic 4 G5 / 2→ 6 H9 / 2 and 4 G5 / 2→ 6 Temperature detection can be achieved by using the fluorescence intensity ratio of the H5 / 2 transition as a function of temperature.

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