High quantum efficiency europium-doped double perovskite fluorescent powder, preparation method and application thereof

Abstract

The application discloses a high-quantum-efficiency europium-doped double-perovskite fluorescent powder, a preparation method and application thereof, and belongs to the technical field of fluorescent materials. 3+ The application provides a novel double-perovskite fluorescent powder Ca2AlTaO6:xmol%Eu 3+ , which has high quantum efficiency and high relative sensitivity, thus having excellent luminescent characteristics and optical temperature measuring capacity, and can be well matched with LED devices, and has important multifunctional application potential in the fields of light-emitting diodes and optical temperature sensors. In addition, the Ca2AlTaO6:xmol%Eu 3+ fluorescent powder provided by the application also has good color temperature stability, and the correlated color temperature (CCT) only has small fluctuations with the change of doping concentration and environmental temperature, which indicates that the material has stable luminescent color quality.

Description

Technical Field

[0001] This invention belongs to the field of fluorescent materials technology, and particularly relates to a high quantum efficiency europium-doped double perovskite phosphor, its preparation method and application. Background Technology

[0002] Phosphors are key light conversion materials in the lighting and display fields, and their performance directly determines the luminous efficiency, color quality, and operational stability of devices. In recent years, with the rapid development of solid-state lighting (such as white LEDs) and optical temperature sensing technology, the development of novel fluorescent materials that combine high quantum efficiency, excellent thermal stability, and multifunctional application potential has become a research hotspot.

[0003] Double perovskite oxides (A₂BB'O₆) are considered ideal luminescent matrix materials due to their unique crystal structure, good physicochemical stability, and flexible cation substitution sites. By doping the A-site or B-site with rare earth ions (such as Eu)... 3 + This allows for effective control of light color. Among them, Eu... 3+ Ions because they have 5 The D0→7F2 characteristic red emission transition is widely used in the development of red phosphors. However, most of the reported Eu... 3+ Doping phosphors still faces many challenges. For example, the common Y₂O₂S:Eu 3+ BaZrGe3O9:Eu 3+ The internal quantum efficiency of these materials is generally low, mostly below 50%, making it difficult to meet the high light conversion efficiency requirements of high-efficiency light-emitting devices. Meanwhile, under high-temperature operating conditions, thermal quenching leads to a significant decrease in the luminous intensity of the phosphor and a shift in color coordinates, severely affecting the color stability and lifespan of the device.

[0004] Furthermore, optical thermometry based on fluorescence intensity ratio (FIR) has attracted considerable attention due to its advantages of being unaffected by excitation power fluctuations and detection conditions. However, existing Eu... 3+ The relative and absolute sensitivities of doped fluorescent temperature sensing materials remain generally low, limiting their application in high-precision temperature detection. For example, existing NaGd(WO4)2:Eu... 3+ and K2CaP2O7:Eu 3+ The relative sensitivity of these materials is all below 5%·K. -1 Therefore, there is an urgent need to develop a novel Eu molecule with high quantum efficiency, excellent thermal stability, and high temperature sensitivity. 3+ Doped double perovskite phosphors are used to meet the multifunctional application requirements of next-generation high-performance optoelectronic devices. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a high quantum efficiency europium-doped double perovskite phosphor, its preparation method, and its applications.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a high quantum efficiency europium-doped double perovskite phosphor, wherein the chemical formula of the europium-doped double perovskite phosphor is Ca2AlTaO6:xmol%Eu 3+ x = 1~24.

[0007] Furthermore, the europium-doped double perovskite phosphor has the chemical formula Ca2AlTaO6:18mol%Eu 3+ .

[0008] Furthermore, the europium-doped double perovskite phosphor exhibits an internal quantum efficiency of 73.96% and a relative sensitivity of 7.29%·K. -1 .

[0009] Furthermore, the europium-doped double perovskite phosphor belongs to the monoclinic crystal system with space group P21 / n; its lattice parameters are a=5.38923Å, b=5.431906Å, c=7.633137Å, α=90.0°, β=90.22699°, γ=90.0°; and its cell volume V=223.45Å. 3 Z=2.0.

[0010] This invention provides a method for preparing a high quantum efficiency europium-doped double perovskite phosphor as described above, comprising the following steps: The raw materials calcium source, aluminum source, tantalum source and europium source were weighed according to the stoichiometric ratio and then ground to obtain a mixture; the mixture was then calcined to obtain the high quantum efficiency europium-doped double perovskite phosphor.

[0011] Furthermore, the calcium source is selected from calcium carbonate; the aluminum source is selected from aluminum oxide; the tantalum source is selected from tantalum pentoxide; and the europium source is selected from europium oxide.

[0012] Furthermore, the grinding process specifically involves: first adding alcohol for wet grinding, and then continuing grinding for 20 minutes after the alcohol has evaporated.

[0013] Furthermore, the calcination specifically involves: pre-sintering at 600°C for 2 hours, followed by calcination at 1500°C for 6 hours.

[0014] The present invention also provides an application of the high quantum efficiency europium-doped double perovskite phosphor as described above in a temperature sensor.

[0015] Compared with the prior art, the present invention has the following advantages and technical effects: This invention provides a novel type of double perovskite phosphor, Ca2AlTaO6:xmol%Eu. 3+ It possesses high quantum efficiency and high relative sensitivity, thus exhibiting excellent luminescence characteristics and optical temperature measurement capabilities. Furthermore, it can be well-matched with LED devices, demonstrating significant potential for multifunctional applications in fields such as light-emitting diodes and optical temperature sensors. In addition, the Ca2AlTaO6:xmol%Eu provided by this invention... 3+ The phosphor also exhibits good color temperature stability, with the correlated color temperature (CCT) fluctuating only slightly with changes in doping concentration and ambient temperature, indicating that the material possesses stable luminescent color quality.

[0016] The Ca2AlTaO6:xmol%Eu provided by this invention 3+ The phosphor boasts an internal quantum efficiency (IQE) of up to 73.96%, exhibiting high efficiency in converting excitation energy into photons and a relatively high luminescence yield, demonstrating potential for applications in high-efficiency light-emitting devices. Furthermore, it retains 74.02% of its initial luminescence intensity at 450K, showcasing excellent thermal stability and promising potential for applications in temperature sensing.

[0017] Under a driving current of 300mA, based on the Ca2AlTaO6:18mol%Eu provided by this invention... 3+ The phosphor-encapsulated WLED device achieves a color rendering index (CRI) of 95.9 and a correlated color temperature (CCT) of 6367.33 K. Meanwhile, Ca2AlTaO6:18mol%Eu 3+ Phosphors also possess excellent optical temperature measurement properties, based on 5 D0→ 7 F2 and 5 D0→ 7 The absolute sensitivity (S) of the F1 transition pair a The maximum value is approximately 0.31K. -1 Relative sensitivity (S r The maximum value is approximately 7.29%·K -1 Compared with previously reported Eu-doped phosphors, the phosphor of this invention is more sensitive to temperature changes, has excellent temperature detection accuracy, and has good potential for optical temperature sensing applications.

[0018] Based on the Ca2AlTaO6:18mol%Eu provided by this invention 3+ LED devices assembled with phosphors exhibit electroluminescence spectra similar to those of chlorophyll b and plant phytochrome P. RF The absorption bands show good matching and overlap, indicating that the material has potential application value in the field of plant growth lighting. Attached Figure Description

[0019] 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 Different concentrations of Eu prepared in Example 1 3+ Doped Ca2AlTaO6:x%Eu 3+ XRD pattern of phosphor; Figure 2 Different concentrations of Eu prepared in Example 1 3+ Doped Ca2AlTaO6:x%Eu 3+ Photoexcitation spectrum of phosphor at 618 nm wavelength; Figure 3 Different concentrations of Eu prepared in Example 1 3+ Doped Ca2AlTaO6:x%Eu 3+ Photoexcitation spectrum of phosphor at 398 nm wavelength; Figure 4 Different concentrations of Eu prepared in Example 1 3+ Doped Ca2AlTaO6:x%Eu 3+ CIE 1931 chromaticity variation of phosphor at a wavelength of 398 nm; Figure 5 Different concentrations of Eu prepared in Example 1 3+ Doped Ca2AlTaO6:x%Eu 3+ CIE x and y values ​​of phosphors; Figure 6 The Ca2AlTaO6:18%Eu prepared in Example 1 3+ Internal quantum efficiency (IQE) of phosphors; Figure 7 The Ca2AlTaO6:18%Eu prepared in Example 1 3+ Fluorescence lifetime of phosphors; Figure 8 The Ca2AlTaO6:18%Eu prepared in Example 1 3+ Fluorescence emission spectrum of phosphor in the range of 300~500K; Figure 9 The Ca2AlTaO6:18%Eu prepared in Example 1 3+ The CIE 1931 color coordinate variation of phosphor in the range of 300~500K; Figure 10 The Ca2AlTaO6:18%Eu prepared in Example 1 3+Contour plot of thermal stability of phosphor; Figure 11 The Ca2AlTaO6:18%Eu prepared in Example 1 3+ The hot quenching mechanism of phosphors; Figure 12 The Ca2AlTaO6:18%Eu prepared in Example 1 3+ Schematic diagram of the thermal quenching mechanism of phosphors; Figure 13 To utilize Ca2AlTaO6:18%Eu 3+ A schematic diagram of the CIE coordinates and isoenergetic point distribution of a WLED device fabricated with phosphor, with an inset showing a physical image of the WLED device; Figure 14 To utilize Ca2AlTaO6:18%Eu 3+ Electroluminescence (EL) spectrum of WLED device fabricated with phosphor, with the inset showing the color rendering index R. a The trend of change with current; Figure 15 To utilize Ca2AlTaO6:18%Eu 3+ The EL spectrum of a red LED device prepared with phosphor at a forward current of 300 mA is compared with that of chlorophyll b and plant phytochrome P. RF The absorption spectrum comparison diagram is shown, and the inset is a picture of a real red LED. Figure 16 The Ca2AlTaO6:18%Eu prepared in Example 1 3+ Temperature-dependent luminescence properties curve of phosphor; Figure 17 The Ca2AlTaO6:18%Eu prepared in Example 1 3+ FIR curve fitting results of phosphors at different temperatures; Figure 18 The Ca2AlTaO6:18%Eu prepared in Example 1 3+ Absolute sensitivity (S) of phosphor at different temperatures a ) and relative sensitivity (S r The fitted curve of ). Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] In this embodiment of the invention, room temperature and normal temperature refer to "25±2℃".

[0023] Unless otherwise specified, all raw materials used in the embodiments of this invention were purchased through commercial channels.

[0024] Example 1 A high quantum efficiency europium-doped double perovskite phosphor with the chemical formula Ca2AlTaO6:xmol%Eu 3+ x = 1, 5, 10, 18, 22 or 24; The specific steps for preparing the above-mentioned europium-doped double perovskite phosphor are as follows: Using high-purity calcium carbonate (CaCO3, 99.99%), alumina (Al2O3, 99.99%), tantalum pentoxide (Ta2O5, 99.99%), and europium oxide (Eu2O3, 99.99%) as raw materials, the raw materials were weighed according to the stoichiometric ratio, placed in an agate mortar, and wet-milled with alcohol. After the alcohol evaporated, grinding continued for 20 minutes to ensure uniform mixing, resulting in a mixture. The mixture was then placed in a muffle furnace and pre-sintered at 600℃ for 2 hours, followed by calcination at 1500℃ for 6 hours. After calcination, the mixture was allowed to cool naturally to room temperature. The sintered block was then ground into fine powder in an agate mortar to obtain Eu oxides of different concentrations. 3+ Doped Ca2AlTaO6: xmol%Eu 3+ Phosphor (abbreviated as Ca2AlTaO6:x%Eu) 3+ The values ​​are: Ca2AlTaO6:1mol%Eu 3+ Phosphor, Ca2AlTaO6:5mol%Eu 3+ Phosphor, Ca2AlTaO6:10mol%Eu 3+ Phosphor, Ca2AlTaO6:18mol%Eu 3+ Phosphor, Ca2AlTaO6: 22mol%Eu 3+ Phosphor, Ca2AlTaO6: 24mol%Eu 3+ Fluorescent powder.

[0025] Figure 1 Different concentrations of Eu prepared in Example 1 3+ Doped Ca2AlTaO6:x%Eu 3+ XRD pattern of the phosphor. From Figure 1It can be seen that the main diffraction peaks of all samples are highly consistent with the standard PDF card (number 04-009-8956) of Ca2AlTaO6, and the position of the main peak does not show a significant shift, confirming that Ca2AlTaO6:x%Eu 3+ The phosphor has been successfully prepared.

[0026] Using Jade software Figure 1 Refined analysis of the XRD data revealed that all samples belonged to the monoclinic crystal system, space group P21 / n, with lattice parameters a=5.38923Å, b=5.431906Å, c=7.633137Å, α=90.0°, β=90.22699°, γ=90.0°, and cell volume V=223.45Å. 3 Z=2.0 indicates that Ca2AlTaO6:x%Eu 3+ All phosphors are pure phases, Eu 3+ The introduction of [a substance] did not cause any change in the crystal structure of Ca2AlTaO6.

[0027] At room temperature, the different concentrations of Eu obtained in Example 1 were monitored at 618 nm. 3+ Doped Ca2AlTaO6:x%Eu 3+ The photoexcitation (PLE) spectrum of the phosphor is shown in the figure. Figure 2 .

[0028] Figure 2 Different concentrations of Eu prepared in Example 1 3+ Doped Ca2AlTaO6:x%Eu 3+ Photoexcitation spectrum of phosphor at 618 nm wavelength. From Figure 2 As can be seen, multiple sets of characteristic excitation peaks exist in the 350~550nm range, distributed at 364nm, 382nm, 398nm, 417nm, 467nm, and 536nm, respectively. These peaks correspond to Eu. 3+ The 4f electronic transition, specifically the ground state 7 F0 is converted to an excited state 5 D4、 5 L7 5 L6 5 D3、 5 D2、 5 The energy level transition of D1 (the characteristic peak shape of the stimulated transition of the 4f orbital electron also confirms Eu) 3+(Stable doping state in the matrix). Among them, the strong excitation peak response in the near-ultraviolet region indicates that the phosphor can match the emission band of commercial near-ultraviolet LED chips and has the potential to be effectively excited by 395nm UV InGaN chips, providing an excitation compatibility basis for its application in white LEDs (WLEDs).

[0029] Figure 3 Different concentrations of Eu prepared in Example 1 3+ Doped Ca2AlTaO6:x%Eu 3+ Photoexcitation spectrum of phosphor at 398 nm wavelength. From Figure 3 It can be seen that Ca2AlTaO6:x%Eu 3+ The phosphor exhibits multiple characteristic emission peaks, mainly concentrated in the 550–750 nm range, with distributions at 583 nm, 595 nm, 618 nm, 656 nm, and 697 nm, corresponding to Eu. 3+ of 5 D0→ 7 F J (J=0, 1, 2, 3, 4) transitions, with the transition located near 618 nm. 5 D0→ 7 The F2 transition peak is the most significant—this strong peak, dominated by the electric dipole transition, directly reflects the Eu... 3+ It exists in a low-symmetry coordination environment within the matrix lattice. The intensity order of each peak is as follows: 5 D0→ 7 F2> 5 D0→ 7 F1> 5 D0→ 7 F4> 5 D0→ 7 F3> 5 D0→ 7 F0 originates from the difference in transition type and response to the local crystal field: 5 D0→ 7 F1 is a magnetic dipole transition (MD, satisfying |ΔL|=1, |ΔJ|=1), which is insensitive to the local crystal field and is the second strongest peak; 5 D0→ 7 F2 5 D0→ 7 F4 is a forced electric dipole transition (FED), which is activated by breaking the parity ban in a non-centrosymmetric crystal field. The former has the highest sensitivity and the strongest intensity. 5 D0→ 7 F0、 5 D0→ 7 F3 is a highly forbidden jump, with extremely weak strength.

[0030] Figure 4 Different concentrations of Eu prepared in Example 1 3+ Doped Ca2AlTaO6:x%Eu 3+ The chromaticity variation of the phosphor at a wavelength of 398 nm according to CIE 1931 standards. Figure 4 It can be seen that, with Eu 3+ With changes in doping concentration, the color coordinates of each sample showed only slight shifts, and the coordinate points highly overlapped, indicating that the phosphor possesses excellent color stability. Among them, the color coordinates of the sample with a doping concentration of 18 mol% were closest to the red region, demonstrating its potential for application in related fields.

[0031] Color temperature (CCT) is a core indicator for evaluating the color quality of luminescent materials, and it can be calculated using the following formula: , Where x and y represent Ca2AlTaO6:x%Eu 3+ The color coordinate position.

[0032] Furthermore, color quality can be further analyzed through color purity. The formula for calculating color purity is: ; In the formula, (x i y i ), (x w y w ), (x z y z The coordinates of the sample are the measured color coordinates, the reference coordinates of the standard white light source (0.333, 0.333), and the color coordinates of the 618nm main wavelength (0.68725, 0.31259), respectively.

[0033] Different concentrations of Eu prepared in Example 1 3+ Doped Ca2AlTaO6:x%Eu 3+ The CIE x and y values ​​of the phosphor are shown in the figure. Figure 5 Different concentrations of Eu prepared in Example 1 3+ Doped Ca2AlTaO6:x%Eu 3+ The CIE, CCT, and color purity of the phosphor are shown in Table 1.

[0034] Table 1 Table 1 shows the results of different concentrations of Eu prepared in Example 1. 3+ Doped Ca2AlTaO6:x%Eu 3+ The color temperature of the phosphor is in the low color temperature range of 1785~2548.19K; when Eu 3+When the doping concentration is 18 mol%, the color purity can reach over 90%, proving that Eu 3+ The activated Ca2AlTaO6 phosphor exhibits excellent color purity.

[0035] Internal quantum efficiency (IQE), as one of the core indicators for measuring the photoelectric conversion efficiency of phosphors and their application prospects in the lighting field, is calculated using the following formula: ; In the formula, η represents the value of the internal quantum efficiency (IQE). L S Represents Ca2AlTaO6:18%Eu 3+ Emission spectrum of phosphor, E R The excitation spectrum representing the reference material BaSO4 (BSO) E S The excitation spectrum represents the phosphor being tested itself.

[0036] Figure 6 The Ca2AlTaO6:18%Eu prepared in Example 1 3+ Internal quantum efficiency (IQE) of phosphors. From Figure 6 It can be seen that at an excitation wavelength of 398 nm, Ca2AlTaO6:18%Eu 3+ The phosphor's internal quantum efficiency (IQE) can reach 73.96%. This high IQE indicates that after the sample absorbs excitation photons, only a very small portion of the energy is dissipated through non-radiative transitions and lattice defect relaxation. The vast majority of the excitation energy is efficiently converted into characteristic red photons, laying a solid foundation for the material's application in high-brightness plant growth LEDs, optical temperature measurement, and other fields.

[0037] Ca2AlTaO6 prepared in Example 1: 18% Eu 3+ Table 2 shows a comparison of the internal quantum efficiency of the phosphor and existing phosphors.

[0038] Table 2 As can be seen from Table 2, the Ca2AlTaO6:18%Eu provided by this invention 3+ Phosphors exhibit the highest internal quantum efficiency, demonstrating excellent luminescent performance and great potential for practical applications.

[0039] Figure 7 The Ca2AlTaO6:18%Eu prepared in Example 1 3+ The fluorescence lifetime of phosphors. From Figure 7 It can be seen that Ca2AlTaO6:18%Eu 3+The fluorescence decay of phosphors exhibits a specific kinetic pattern, characterized by rapid decay in the initial stage, followed by slow decay until it stabilizes.

[0040] Using a single exponential function on Eu 3+ Fitting was performed using Ca2AlTaO6:18%Eu 3+ The fluorescence decay process of phosphors is represented by the following equation: ; In the formula, I(t) is the fluorescence intensity of the sample at time t. A Let be the fitting constant. t To measure time, τ This represents the fluorescence lifetime value. The above equation was used for fitting calculation, and the results show that Ca2AlTaO6:18%Eu 3+ Its fluorescence lifetime is 0.910 ms. This relatively short decay time characteristic makes it well-suited for applications in the field of white light-emitting diodes (WLEDs).

[0041] Under 398 nm excitation, the Ca2AlTaO6:18%Eu obtained in Example 1 was tested. 3+ The temperature-dependent emission spectrum of the phosphor was tested in the range of 300–500 K. Results are shown below. Figure 8 .

[0042] Figure 8 The Ca2AlTaO6:18%Eu prepared in Example 1 3+ The fluorescence emission spectrum of the phosphor in the range of 300–500 K. From Figure 8 It can be seen that as the temperature increases, Ca2AlTaO6:18%Eu 3+ The phosphor exhibits excellent thermal stability at its characteristic emission peak intensity at 618 nm, and the peak shape and energy position of all emission peaks show no significant shift. This indicates that the electronic transition energy level structure of the phosphor is unaffected by thermal disturbances within the test temperature range and can maintain stable luminescence under high-temperature operating conditions. Ca2AlTaO6:18%Eu 3+ The main emission peak of the phosphor originates from Eu 3+ Ionic 5 D0→ 7 The intensity of the F2 electric dipole transition decreases monotonically with increasing temperature, but the centroid of the emission peak does not shift significantly, and the dominant transition properties remain unchanged.

[0043] Figure 9 The Ca2AlTaO6:18%Eu prepared in Example 1 3+ The CIE1931 color coordinate variation of phosphor in the range of 300~500K.

[0044] Ca2AlTaO6 prepared in Example 1: 18% Eu 3+ The chromaticity coordinates, CCT, and color purity of the phosphor in the temperature range of 300~500K are shown in Table 3.

[0045] Table 3 Depend on Figure 9 As shown in Table 3, with increasing temperature, Ca2AlTaO6:18%Eu 3+ The phosphor's color coordinates showed almost no shift, indicating that it maintains stable color quality even at high temperatures, demonstrating its potential as a red phosphor for near-ultraviolet (NUV) excited white LEDs. Furthermore, throughout the entire test temperature range, Ca2AlTaO6:18%Eu 3+ The correlated color temperature (CCT) of the phosphor is stable at 2390.89~2628.98K, and the color purity is as high as 91.01% or more. This result confirms that the phosphor can continuously emit high-purity red light under high-temperature operating conditions, and can provide a stable red light-emitting component for white LEDs.

[0046] Figure 10 The Ca2AlTaO6:18%Eu prepared in Example 1 3+ Contour plot of the thermal stability of phosphor. Figure 10 The expression Ca2AlTaO6:18%Eu was clearly presented. 3+ The luminescence intensity of the phosphor was varied within a temperature range of 300–500 K. The results showed that as the test temperature increased, the luminescence intensity of Ca2AlTaO6:18%Eu... 3+ The phosphor exhibits a regular decrease in luminescence intensity at its characteristic emission peak of 618 nm, a phenomenon perfectly consistent with the typical behavior of thermo-induced fluorescence quenching. The underlying mechanism is that increased temperature induces intensified lattice vibrations, enhancing the phonon energy within the material and thus promoting Eu quenching. 3+ Ions from excited state 5 Nonradiative transitions from D0 to the ground state (such as phonon-assisted level relaxation) ultimately reduce the probability of radiative transitions, leading to a decrease in luminescence intensity. Despite this, the material maintains considerable luminescence intensity at 500 K, and combined with its characteristic of no significant shift in peak shape and position over a wide temperature range, further confirms the presence of Ca2AlTaO6:18%Eu 3+ Phosphors possess excellent thermal stability, providing crucial performance support for their application in high-temperature operating scenarios such as high-power WLEDs.

[0047] Figure 11 The Ca2AlTaO6:18%Eu prepared in Example 1 3+ The thermal quenching mechanism of phosphors. From Figure 11 It can be seen from this that Ca2AlTaO6:18%Eu 3+ The phosphor exhibits excellent thermal stability. At the typical operating temperature of WLED 450K, the intensity of its 618nm characteristic emission peak can still maintain 74.02% of the initial value, and at 350K it can retain 95.00% of the luminescence intensity. This performance is significantly better than most conventional red phosphors.

[0048] T is a core indicator for measuring a material's resistance to thermal quenching. 0.5 This refers to the temperature at which the luminous intensity decays to 50% of room temperature; a higher value indicates better performance. Test results show that Ca2AlTaO6:18%Eu 3+ T 0.5 Above 500K, above Y2Mo4O 15 Eu 3+ (487K, A synergistic anionic substitution strategy forsimultaneously enhanced red emission and thermal stability in Y2Mo4O 15 Eu 3+ phosphors) and SrBi2TeO7:Eu 3+ (403K, SrBi2TeO7:Eu) 3+ : a novel blue-light excitablered-emitting phosphor for solid-state lighting) and NaCaTiTaO6:Eu 3+ (480K, The performance tuning of NaCaTiTaO6:Dy 3+ Eu 3+ (phosphorus by employing the co-doping strategy for white LED application). The above results fully demonstrate that Ca2AlTaO6:18%Eu 3+ Phosphors possess excellent thermal stability, a characteristic that makes them highly promising for applications in high-temperature environments such as high-power WLEDs.

[0049] Figure 12 The Ca2AlTaO6:18%Eu prepared in Example 1 3+ A schematic diagram of the thermal quenching mechanism of phosphors. From Figure 12It can be seen that, under normal temperature conditions, after excitation by 398nm ultraviolet light, Eu 3+ ground state 7 Electrons in the F0 energy level absorb photons and transition to a higher-energy excited state. 5 L6; Subsequently, under the influence of the lattice field, the excited-state electrons rapidly relax to a metastable state through nonradiative relaxation. 5 D0; Ultimately, metastable state 5 Electrons at D0 undergo radiative transitions, releasing visible light (i.e., process ①, corresponding to...). 5 D0→ 7 F J (J=0, 1, 2, 3, 4)), where 5 The D0→7F2 electric dipole transition produces a main emission peak at 618 nm, and electrons return to the ground state. 7 F0 completes the luminescence cycle. As the temperature increases, the lattice vibrations of the Ca2AlTaO6 matrix intensify, transforming into Eu through phonon transfer. 3+ Provides additional heat energy. At this point, metastable state... 5 Some electrons on D0 absorb thermal energy. When the energy reaches the activation barrier of 0.247 eV, they will cross the barrier through path ② and enter the intersection region of the excited state and the charge transfer band (CTB). Electrons in this region cannot return to the ground state through radiative transition. Instead, they transfer energy to the lattice in the form of phonons through multiphonon-assisted relaxation (process ③), and finally dissipate it as thermal energy.

[0050] To evaluate Ca2AlTaO6:18%Eu 3+ The application potential of phosphors in white LEDs, comparing this phosphor with commercial green phosphors (BaSiO4:Eu). 2+ ), commercial blue phosphor BAM (BaMgAl) 10 O 17 Eu 2+ The mixture was prepared at a mass ratio of 800:1:1, encapsulated on a 395nm excited LED chip, and cured to obtain a WLED device. A physical image of the WLED device can be found here. Figure 12 The illustrations in the figure show the results of testing the fabricated WLED device under a driving voltage of 3V and a current of 200~500mA. Figures 13-14 .

[0051] Figure 13 To utilize Ca2AlTaO6:18%Eu 3+ A schematic diagram of the CIE coordinates and isoenergetic point distribution of a WLED device fabricated with phosphor. The inset shows a physical image of the WLED device. Figure 13 The results show that using Ca2AlTaO6:18%Eu 3+WLED devices made of phosphors can emit bright white light when driven by a current of 300mA, and their correlated color temperature (CCT) reaches 6367.33K.

[0052] Using Ca2AlTaO6:18%Eu 3+ The chromaticity coordinate parameters of the WLED device fabricated with phosphor are shown in Table 4.

[0053] Table 4 Table 4 shows that using Ca2AlTaO6:18%Eu 3+ The WLED device fabricated with phosphor is located close to the standard white light reference point in chromaticity coordinates when driven by a 300mA current.

[0054] Figure 14 To utilize Ca2AlTaO6:18%Eu 3+ Electroluminescence (EL) spectrum of WLED device fabricated with phosphor, with the inset showing the color rendering index R. a The trend of change with current. From Figure 14 The spectrum clearly shows the corresponding Eu 3+ ion 5 D0→ 7 F J Five characteristic emission peaks (J=0, 1, 2, 3, 4) transitions. The color rendering index R of this WLED device varies under different driving currents. a All values ​​remained within the range of 91.2 to 95.9, exhibiting stable and excellent color rendering performance; the color rendering index R... a The trend of R changing with current is shown in the illustration. It can be seen that its R a The highest value can reach 95.9. The above test results confirm that Ca2AlTaO6:18%Eu 3+ Phosphors have demonstrated excellent optical performance and promising application prospects in the field of white light-emitting diodes.

[0055] To evaluate Ca2AlTaO6:18%Eu 3+ The application potential of phosphors in red LEDs was explored by coating the phosphor onto a 395nm UV InGaN chip, followed by curing and encapsulation to fabricate an LED device. A physical image of the LED device can be found here. Figure 15 The illustrations in the figure show the results of testing the fabricated LED device under a driving voltage of 3V and a current of 300mA. Figure 15 .

[0056] Figure 15 To utilize Ca2AlTaO6:18%Eu 3+The EL spectrum of a red LED device prepared with phosphor at a forward current of 300 mA is compared with that of chlorophyll b and plant phytochrome P. RF The absorption spectrum comparison diagram is shown, with the inset being a physical image of a red LED. From Figure 15 It can be seen that the emission spectrum of LED devices is related to that of plant photosensitive pigments (P... RF The absorption spectra are well matched. The inset clearly shows the light emission of the LED under 395nm chip excitation, demonstrating that the device emits bright red light with excellent luminous intensity. These results confirm that Ca2AlTaO6:18%Eu 3+ Phosphors have the potential to be used in plant growth lights and are a promising candidate material for the field of LED plant cultivation.

[0057] Figure 16 The Ca2AlTaO6:18%Eu prepared in Example 1 3+ Temperature-dependent luminescence properties of phosphor. Figure 16 It can be seen that within the temperature range of 300~500K, Eu 3+ ion 5 D0→ 7 The intensity decay rate of the F2 electric dipole transition is significantly faster than that of the F2 electric dipole transition. 5 The difference in intensity between the D0→7F1 magnetic dipole transition and the two transitions provides a basis for optical thermometry in this material. Temperature changes can significantly regulate key spectral parameters such as emission peak position, full width at half maximum (FWHM), luminescence intensity, and lifetime of the luminescence center through physical mechanisms such as intensifying lattice thermal vibrations and altering energy relaxation paths. The thermal response characteristics of these parameters can be directly mapped to the spectral output.

[0058] To overcome the limitations of a single intensity index being susceptible to fluctuations in the excitation source and interference from detector responsivity, this invention introduces the Fluorescence Intensity Ratio (FIR) technique, selecting Eu... 3+ Ionic 5 D0→ 7 F2 and 5 D0→ 7 The intensity ratio of the F1 transition is used as a temperature-sensing characteristic parameter. This ratio has an intrinsic property of being temperature-dependent, which can effectively eliminate interference from external environmental factors. Its temperature dependence can be fitted by the following equation, and the results are shown in [the table below]. Figure 17 : ; In the formula, A B is a constant related to the intrinsic luminescence properties of the material, and Δ is the pre-exponential factor. E The activation energy between energy levels K BBoltzmann constant ( K B =1.380649×10 -23 J / K), T It is the thermodynamic temperature.

[0059] Figure 17 The Ca2AlTaO6:18%Eu prepared in Example 1 3+ The FIR curve fitting results of the phosphor at different temperatures. The fitting results in the figure show the coefficient of determination R of the FIR curve. 2 =0.99, indicating that the experimental data are in high agreement with the theoretical model.

[0060] Absolute sensitivity (S a ) and relative sensitivity (S r S is a core indicator for evaluating the performance of optical temperature measurement. a S is the first derivative of FIR with respect to temperature, reflecting the absolute rate of change of FIR with temperature; r For S a The ratio of FIR to FIR reflects the relative response magnitude of FIR to temperature changes and is directly related to the temperature measurement resolution. Based on the FIR-T fitting equation, we can obtain: ; .

[0061] Figure 18 The Ca2AlTaO6:18%Eu prepared in Example 1 3+ Absolute sensitivity (S) of phosphor at different temperatures a ) and relative sensitivity (S r The fitted curve of ). Figure 18 The results show that, targeting 5 D0→ 7 F2 and 5 D0→ 7 F1 transition pair, Ca2AlTaO6:18%Eu 3+ The relative sensitivity (S) of phosphors r The maximum value is approximately 7.29%·K -1 Absolute sensitivity (S a The maximum value is approximately 0.31K. -1 .

[0062] Ca2AlTaO6 obtained in Example 1: 18%Eu 3+ The relative sensitivity (S) of phosphors compared to some previously reported phosphors r ) and absolute sensitivity (S a The comparison is shown in Table 5.

[0063] Table 5 Table 5 shows that the Ca2AlTaO6:18%Eu provided by this invention... 3+ The relative sensitivity of phosphors in the same Eu class 3+ The doped oxide phosphor is at a relatively high level, and its absolute sensitivity can meet the response rate requirements for real-time temperature measurement in the medium and low temperature range (300~500K).

[0064] 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 high quantum efficiency europium-doped double perovskite phosphor, characterized in that, The chemical formula of the europium-doped double perovskite fluorescent powder is Ca2AlTaO6:x mol% Eu 3+ , x = 1-24.

2. The high quantum efficiency europium-doped double perovskite phosphor according to claim 1, characterized in that, The chemical formula of the europium-doped double perovskite fluorescent powder is Ca2AlTaO6: 18mol%Eu 3+ .

3. The high quantum efficiency europium-doped double perovskite phosphor according to claim 2, characterized in that, The europium-doped double perovskite phosphor has an internal quantum efficiency of 73.96% and a relative sensitivity of 7.29%·K. -1 .

4. The high quantum efficiency europium-doped double-perovskite phosphor of claim 1, wherein, The europium-doped double perovskite phosphor belongs to the monoclinic crystal system with space group P21 / n; its lattice parameters are a=5.38923Å, b=5.431906Å, c=7.633137Å, α=90.0°, β=90.22699°, γ=90.0°; and its cell volume V=223.45Å. 3 Z=2.

0.

5. A method for preparing high quantum efficiency europium-doped double perovskite phosphor according to any one of claims 1 to 4, characterized in that, Includes the following steps: The raw materials calcium source, aluminum source, tantalum source and europium source were weighed according to the stoichiometric ratio and then ground to obtain a mixture; the mixture was then calcined to obtain the high quantum efficiency europium-doped double perovskite phosphor.

6. The production method according to claim 5, wherein The calcium source is selected from calcium carbonate; the aluminum source is selected from aluminum oxide; the tantalum source is selected from tantalum pentoxide; and the europium source is selected from europium oxide.

7. The preparation method according to claim 5, characterized in that, The grinding process involves first adding alcohol for wet grinding, and then continuing grinding for another 20 minutes after the alcohol has evaporated.

8. The preparation method according to claim 5, characterized in that, The calcination process specifically involves: pre-sintering at 600℃ for 2 hours, followed by calcination at 1500℃ for 6 hours.

9. The application of a high quantum efficiency europium-doped double perovskite phosphor as described in any one of claims 1 to 4 in a temperature sensor.

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