White long-afterglow luminescent material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of luminescent materials, and particularly relates to a white long-afterglow luminescent material as well as a preparation method and application thereof. The molecular formula of the white long-afterglow luminescent material is NaSr2GaGe5O14: Pr < 3 + >, Pr < 3 + > is an activator, and NaSr2GaGe5O14 is a matrix. The luminescent material provided by the invention has more advantages in the aspect of chemical stability, is not easily influenced by environmental factors such as water, oxygen and the like to cause reduction of luminescent property, and can be used under wider environmental conditions. In addition, the fluorescent powder also has the advantages of good white light-emitting characteristic, excellent long afterglow performance, high light-emitting stability, strong spectrum adjustability and the like.

Description

Technical Field

[0001] The present application belongs to the technical field of luminescent materials, and specifically relates to a white long afterglow luminescent material and a preparation method and application thereof. Background Art

[0002] Long-lasting luminescent materials are a class of materials that can store energy from external light radiation and slowly release this stored energy as visible light at room temperature when exposed to ultraviolet or visible light. This long-lasting luminescence phenomenon stems from defect energy levels caused by doping. During the excitation phase, these defect energy levels capture holes or electrons. After excitation, these electrons or holes are released due to thermal motion, transferring energy to activated ions, causing them to emit light. This slow thermal release results in a long-lasting luminescence characteristic.

[0003] The light emitted by white long-afterglow luminescent materials is close to natural light. In the lighting field, it can provide more comfortable and natural light. In the display field, it can serve as an ideal backlight source to improve the brightness and color reproduction of the display effect. It has unique advantages in places where a natural lighting environment needs to be created and in equipment with high requirements for color display. In the field of safety signs, signboards made of white long-afterglow materials can be more clearly identified under various lighting conditions and can effectively serve as warnings and guides, such as in tunnels, mines, construction sites and other environments. White long-afterglow luminescent materials also have potential application value in some special inspection and treatment environments in the medical field, as well as in fields with strict lighting requirements such as aerospace. Although white long-afterglow luminescent materials have broad application prospects in many fields, they also have the following shortcomings: 1. Limited afterglow time: Although some white long-afterglow luminescent materials can achieve afterglow times of several hours or even more than ten hours, in certain specific application scenarios, a longer afterglow time may still be required. In addition, the afterglow time of some materials may be affected by environmental factors such as temperature and humidity, further limiting their practical applications.

[0004] 2. Poor color stability: Most organic long-lasting luminescent materials achieve white afterglow based on excimer complexes. This system requires a complex multi-component system. Although it can achieve a certain degree of white afterglow, the duration and color stability of the afterglow may be affected.

[0005] 3. Luminous intensity and afterglow intensity need to be improved: For some white, long-afterglow luminescent materials, as internal defects are reduced, the afterglow time remains unchanged, but the luminous intensity and afterglow intensity decrease. This is due to the reduction of internal defects during the material crystallization process. In some applications requiring high-brightness afterglow, such as large outdoor billboards or nighttime signs, lower luminous intensity and afterglow intensity may not meet actual needs.

[0006] 4. Complex preparation processes: Currently, the preparation methods for many long-lasting white luminescent materials are complex, involving multiple methods such as gel-combustion and hydrothermal synthesis. These methods often require strict control of process conditions, such as specific reaction temperature, time, and doping concentration. In addition, some methods also require the use of specialized equipment and raw materials, increasing the cost and difficulty of preparation. Summary of the Invention

[0007] The purpose of the present invention is to solve at least one problem in the prior art and provide a white long afterglow luminescent material and a preparation method and application thereof, specifically adopting the following technical solutions: In the first aspect, the present invention provides a white long afterglow luminescent material, the molecular formula of which is NaSr2GaGe5O 14 :Pr 3+ , where Pr 3+ As activator, NaSr2GaGe5O 14 As the matrix.

[0008] The NaSr2GaGe5O used in the present invention 14 The matrix has a unique crystal structure that can 3+ ions provide a suitable lattice environment, which is beneficial for Pr 3+ The stability and symmetry of its crystal structure can make Pr 3 + The ions form a specific energy level structure in it, thus achieving white long afterglow luminescence. 3+ The ions have rich energy level transitions and produce luminescence of various wavelengths in a suitable matrix, which is similar to NaSr2GaGe5O 14 The interaction of the matrix can achieve white light emission, and Pr 3+ Ion doping may also introduce new trap energy levels, which helps to improve the long afterglow performance of the material.

[0009] As a further preferred embodiment, the NaSr2GaGe5O 14 :Pr 3+ The Pr content is 2.4%.

[0010] In a second aspect, the present invention provides a method for preparing the above-mentioned white long-lasting luminescent material, comprising the following steps: Anhydrous sodium carbonate, strontium carbonate, germanium oxide, gallium oxide, and praseodymium oxide were used as raw materials, placed in a mortar, added with anhydrous ethanol, mixed and ground for the first time, calcined for the first time after grinding, and cooled to room temperature to obtain a sample powder; The sample powder is ground for a second time, and then calcined for a second time after the grinding is completed. After the calcination is completed, the sample powder is cooled to room temperature. After the cooling is completed, the sample powder is ground for a third time to obtain the white long afterglow luminescent material.

[0011] As a further preferred embodiment, the dosage ratio of anhydrous sodium carbonate, strontium carbonate, germanium oxide, gallium oxide, praseodymium oxide and anhydrous ethanol is 0.25 mmol: 0.98 mmol: 0.25 mmol: 2.5 mmol: 0.42 μmol-8.3 μmol: 10 mL. 3+ The amount added is small), the number of traps is small, the number of luminescence centers is small, and the afterglow brightness is low. At low concentrations, the trap energy levels are not fully filled, the carriers are released quickly, and the afterglow lifetime is short. At high concentrations, Pr 3+ The increase of luminous centers will increase the brightness of afterglow, but Pr 3+ The distance between them is shortened, and the excitation energy can be released through cross relaxation. 3 P0→ 3 H6 transfers to adjacent ions or defects, resulting in enhanced non-radiative transitions and reduced luminescence efficiency, which in turn reduces the initial afterglow brightness. At high concentrations, this can lead to excessively deep trap levels or blocked carrier migration paths, accelerating the recombination rate and shortening the afterglow lifetime. 3+ When the addition amount of praseodymium oxide is 20 μmol (the addition amount of praseodymium oxide is 3.3 μmol), the appropriate Pr 3+ As the number of luminescence centers, Pr 3+ and the trap glows together, Pr 3+ The concentration of Pr is matched with the trap energy level, forming the highest efficiency of electron-hole recombination. 3+ The luminescence and radiation transition efficiency reach the best balance, so it shows high afterglow brightness. At this concentration, Pr 3+ The concentration density matches the trap energy level, the appropriate trap energy level depth is 0.768 eV, and the balance between the trap and the luminescence center allows the carriers to be released slowly, thus extending the afterglow time.

[0012] As a further preferred embodiment, the usage ratio of anhydrous sodium carbonate, strontium carbonate, germanium oxide, gallium oxide, praseodymium oxide and anhydrous ethanol is 0.25 mmol: 0.98 mmol: 0.25 mmol: 2.5 mmol: 3.3 μmol: 10 mL.

[0013] As a further preferred embodiment, the temperature of the first calcination is 450°C-550°C; the temperature of the second calcination is 950°C-1050°C.

[0014] As a further preferred embodiment, the temperature of the first calcination is 550°C.

[0015] As a further preferred embodiment, the calcination temperature is 1025°C. The calcination temperature plays a very important role in constructing a suitable number and depth of traps for long afterglow materials, because it determines the crystallinity, defect structure and trap distribution of the material. When the calcination temperature is low, the crystallization of the material is imperfect, and the defects or trap energy levels of the matrix are generally shallow, resulting in premature release of electrons and weak afterglow performance. When the calcination temperature is 1025°C, the crystallinity improves as the temperature gradually increases, the trap depth and density are moderate, the ability to capture electrons is enhanced, and the ability to release electrons is moderate, showing strong long afterglow performance. When the calcination temperature exceeds 1025°C, lattice distortion or defect aggregation occurs, the trap energy levels are too deep or the density is too high, which makes it difficult to release electrons and reduces the afterglow performance.

[0016] As a further preferred embodiment, the time for the first grinding, the second grinding and the third grinding is 25 min-35 min.

[0017] In a third aspect, the present invention provides the use of the above-mentioned white long-afterglow luminescent material in the preparation of white long-afterglow luminescent products.

[0018] The beneficial effects of the present invention are: (1) The present invention provides a NaSr2GaGe5O synthesized by doping with a single matrix and a single rare earth ion. 14 :Pr 3+ White long afterglow luminescent material. Among them, NaSr2GaGe5O 14 It has good chemical stability. Compared with some traditional long afterglow luminescent materials such as sulfide system and some aluminate system, NaSr2GaGe5O 14 : Pr 3+ The material has advantages in chemical stability and is not easily affected by environmental factors such as water and oxygen, which can lead to a decrease in luminescence performance. It can also be used in a wider range of environmental conditions. In addition, it has the advantages of good white luminescence characteristics, long afterglow performance, high luminescence stability and strong spectral tunability.

[0019] (2) The material provided by the present invention produces white luminescence after 10 minutes of ultraviolet excitation at 254 nm and the afterglow time is 4000 s. 3+ The afterglow color changes from blue to white as the concentration increases within the addition range of 2.5 μmol to 50 μmol. The rich afterglow colors and excellent afterglow properties of this material provide new ideas for the design and synthesis of long-lasting white luminescent materials.

[0020] (3) The synthesis method provided by the present invention is easy to operate and synthesize, and has a series of advantages such as preparing high-efficiency afterglow initial value and high color purity white long afterglow luminescent material. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 The results show that NaSr2GaGe5O with different calcination temperatures and different addition amounts 14 :Pr 3+ XRD pattern of Figure 2 Shown is NaSr2GaGe5O 14 :2.0% Pr 3+ SEM images and electron microscope images; Figure 3 Shown is NaSr2GaGe5O 14 :2.0% Pr 3+ Mapping diagram; Figure 4 Shown is NaSr2GaGe5O 14 :Pr 3+ :2.0% Pr 3+ EDS diagram and element content diagram; Figure 5 Shown is NaSr2GaGe5O 14 :Pr 3+ :2.0% Pr 3+ XPS graph; Figure 6 Shown are different addition amounts of NaSr2GaGe5O 14 :x % Pr 3+ Excitation and emission spectra of Figure 7 Shown are different addition amounts of NaSr2GaGe5O 14 :x % Pr 3+ CIE diagram of emission spectrum; Figure 8 The figure shows different amounts of NaSr2GaGe5O 14 :x % Pr 3+ Afterglow excitation and emission spectra; Figure 9 Shown are different addition amounts of NaSr2GaGe5O14 :x % Pr 3+ Afterglow emission CIE diagram; Figure 10 Shown are the afterglow time decay curves for different addition amounts; Figure 11 Shown are afterglow decay photos of different addition amounts after 254 nm ultraviolet excitation for 10 minutes; Figure 12 Shown is NaSr2GaGe5O 14 :2.0% Pr 3+ High temperature variable temperature thermoemission spectrum; Figure 13 Shown is NaSr2GaGe5O 14 :2.0% Pr 3+ High temperature Gaussian peak fitting diagram; Figure 14 Shown is NaSr2GaGe5O 14 :2.0% Pr 3+ Schematic diagram of the afterglow luminescence process. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0024] Example 1 A white long afterglow luminescent material, the preparation method of which specifically comprises the following steps: (1) Weigh 0.25 mmol Na2CO3, 0.98 mmol SrCO3, 0.25 mmol Ga2O3, 2.5 mmol GeO2, and 3.3 μmol Pr6O 11 (Pr 3+ The dosage is 20 μmol) was placed in a mortar, 10 ml of anhydrous ethanol was added and then fully ground for 30 min; (2) The raw material sample ground in step (1) was pre-calcined in a muffle furnace at 500 °C for 4 h, cooled to room temperature, and then placed in a mortar and ground for 30 min; (3) The sample ground in step (2) was pre-calcined in a muffle furnace at 500 °C for 4 h, cooled to room temperature, and then placed in a mortar and ground for another 30 min. (4) The sample ground in step (3) was placed in a muffle furnace and calcined at 1025°C for 4 h, then cooled to room temperature, placed in a mortar and ground for 30 min to obtain a white long afterglow luminescent material with uniform particles.

[0025] The obtained white long afterglow luminescent material was irradiated under 254 nm ultraviolet light for 10 min, and a white long afterglow luminescent material with a white duration of 4000 s was observed.

[0026] Example 2 A white long afterglow luminescent material, the specific preparation process of which is similar to that of Example 1, the only difference being that the raw material Pr6O in step (1) is 11 The dosage was changed to 0.42 μmol (Pr 3+ The dosage is 2.5 μmol).

[0027] Example 3 A white long afterglow luminescent material, the specific preparation process of which is similar to that of Example 1, the only difference being that the raw material Pr6O in step (1) is 11 The dosage was changed to 0.83 μmol (Pr 3+ The dosage is 5 μmol).

[0028] Example 4 A white long afterglow luminescent material, the specific preparation process of which is similar to that of Example 1, the only difference being that the raw material Pr6O in step (1) is 11 The dosage was changed to 1.25 μmol (Pr 3+ The dosage is 7.5 μmol).

[0029] Example 5 A white long afterglow luminescent material, the specific preparation process of which is similar to that of Example 1, the only difference being that the raw material Pr6O in step (1) is 11 The dosage was changed to 1.66 μmol (Pr 3+ The dosage is 10 μmol).

[0030] Example 6 A white long afterglow luminescent material, the specific preparation process of which is similar to that of Example 1, the only difference being that the raw material Pr6O in step (1) is 11 The dosage was changed to 5 μmol (Pr 3+ The dosage is 30 μmol).

[0031] Example 7 A white long afterglow luminescent material, the specific preparation process of which is similar to that of Example 1, the only difference being that the raw material Pr6O in step (1) is 11 The dosage was changed to 6.7 μmol (Pr 3+The dosage is 40 μmol).

[0032] Example 8 A white long afterglow luminescent material, the specific preparation process of which is similar to that of Example 1, the only difference being that the raw material Pr6O in step (1) is 11 The dosage was changed to 8.3 μmol (Pr 3+ The dosage is 50 μmol).

[0033] Example 9 A white long afterglow luminescent material, the specific preparation process of which is similar to that of Example 1, the only difference being that the calcination temperature in step (4) is changed from 1025°C to 950°C.

[0034] Example 10 A white long afterglow luminescent material, the specific preparation process of which is similar to that of Example 1, the only difference being that the calcination temperature in step (4) is changed from 1025°C to 1000°C.

[0035] Example 11 A white long afterglow luminescent material, the specific preparation process of which is similar to that of Example 1, the only difference being that the calcination temperature in step (4) is changed from 1025°C to 1035°C.

[0036] Example 12 A white long afterglow luminescent material, the specific preparation process of which is similar to that of Example 1, the only difference being that the calcination temperature in step (4) is changed from 1025°C to 1050°C.

[0037] Characterization tests were performed on the white long afterglow luminescent materials prepared in the above embodiments: Figure 1 The results show that NaSr2GaGe5O with different calcination temperatures and different addition amounts 14 :Pr 3+ The XRD pattern shows that, compared with the diffraction peaks of the standard card PDF#49-0273 in the JCPDS (Journal of Powder Diffraction Standards), weaker impurity peaks appear at 2-Theta around 24°, 26°, and 30° when the calcination temperature is 950-1000°C. However, there are almost no impurity peaks when the calcination temperature is 1025-1050°C. At this calcination temperature, the peaks of the sample match those of the standard card, indicating that a pure phase crystal structure has been synthesized. 3+ There is no new diffraction peak after the addition of Pr 3+ Doping does not produce a new phase in the matrix NSGGO, indicating that pure phase NSGGO can be synthesized within this addition amount range.

[0038] Figure 2Shown is NaSr2GaGe5O 14 :2.0% Pr 3+ SEM and electron microscope images; it can be seen from the figure that the morphology of the white long afterglow luminescent material belongs to that of a typical high-temperature calcined synthetic sample, which is characterized by irregular, severely agglomerated, and micron-sized particles.

[0039] Figure 3 Shown is NaSr2GaGe5O 14 :2.0% Pr 3+ The mapping diagram shows that the elements are evenly distributed on the sample, which further proves that the sample contains all the elements we need.

[0040] Figure 4 Shown is NaSr2GaGe5O 14 :2.0% Pr 3+ EDS diagram and element content diagram; It can be seen from the figure that the sample contains all elements such as Na, Sr, Ga, Ge, O, Pr and their relative contents, which can explain the Pr 3+ Can be successfully doped into the matrix lattice.

[0041] Figure 5 Shown is NaSr2GaGe5O 14 :2.0% Pr 3+ XPS graph; it can be seen from the figure that a series of binding energy emission peaks corresponding to Na 1s, Sr 3d, Ga 2p, Ge 3d, O 1s, and Pr 3d appear in the binding energy range of 0-1200 eV, and the binding energy is within the normal range.

[0042] Example 13 The fluorescent luminescence properties and afterglow luminescence properties of the white long afterglow luminescent materials prepared in the above embodiments were studied. The specific process is as follows: (1) The long-lasting luminescent materials prepared by doping with different concentrations of rare earth ions were subjected to a series of tests on fluorescence and afterglow spectra in a steady-state transient fluorescence spectrometer (FLS980). The specific test content is to explore the changes in the excitation wavelength in the range of 200-400nm at an emission wavelength of 646nm, and to test the emission wavelength and CIE changes in the range of 420-800nm ​​at an excitation wavelength of 254nm.

[0043] (2) The long-lasting luminescent materials prepared by doping with different concentrations of rare earth ions were subjected to a series of tests on the afterglow time in a long-lasting phosphor tester (PR-305). The specific test content was to continuously excite the materials at an excitation wavelength of 254nm for 10 minutes to explore the afterglow time of the long-lasting luminescent materials.

[0044] The results are as follows Figures 6-11 As shown in the figure, the NaSr2GaGe5O 14 :Pr 3+ White long afterglow luminescent material, by changing Pr 3+ The addition amount can achieve coordinated multicolor fluorescence from blue to cool white to warm white, with long-lasting luminescence, showing potential for anti-counterfeiting applications. When added at 2.0% (20 μmol), it exhibits the highest initial brightness and longest afterglow time, reaching 110 mcd / m² and a long afterglow time of 4000 s. The CIE values ​​for afterglow time (0.315, 0.325) are very close to those of traditional white long-lasting CIE values ​​(0.333, 0.333). White afterglow photos captured by mobile phones confirm the synthesis of this synthetic white long-lasting luminescent material.

[0045] Figure 12 Shown is NaSr2GaGe5O 14 :2.0% Pr 3+ High temperature variable temperature thermoluminescence spectrum; As can be seen from the figure, NSGGO: 2.0% Pr 3+ In the test range of 298-450 K, there is an asymmetric pyroelectric peak, which is composed of two emission peaks superimposed. It is strongest at room temperature. As the test temperature increases, the pyroelectric peak moves toward the high temperature direction, and the peak value gradually decreases.

[0046] Figure 13 Shown is NaSr2GaGe5O 14 :2.0% Pr 3+ High temperature Gaussian peak fitting diagram; As can be seen from the figure, NSGGO:2.0%Pr 3+ Gaussian peak fitting shows two pyroelectric peaks at 344K and 384K. According to the equation E = Tm / 500 proposed by Urbach, the corresponding trap depths of each pyroelectric temperature peak are estimated to be 0.688 eV and 0.768 eV respectively. The depth and number of the two traps are optimal, which can stably store carriers and slowly release electrons at room temperature, thus having excellent long afterglow performance.

[0047] Figure 14 Shown is NaSr2GaGe5O 14 :2.0% Pr 3+Schematic diagram of the afterglow luminescence process. As can be seen from the figure, when the long afterglow luminescent material is excited by 254nm ultraviolet light, the low-energy ground state conduction band electrons are successfully excited to the conduction band. At this time, the electrons have high energy, represented by 1. Most of the high-energy electrons directly jump back to the ground state, thereby emitting red fluorescence, represented by 2. Some of the electrons are captured by traps near the bottom of the conduction band and holes above the valence band. This process is represented by 3a and 3b. Some electrons cross-relax to Pr 3+ excited state 3 P J（0,1,2） and 1 D2 energy level, and returns to the ground state to emit fluorescence, which is represented by 2a. When the UV lamp is turned off, under the action of thermal disturbance, the electrons captured in the shallow trap are first released quickly, escape to the conduction band and mainly emit fluorescence. 3 P0→ 3 H4 transition, accompanied by 1 P0→ 3 F2, 1 P0→ 3 The H6 transition back to the ground state results in a long blue afterglow, and the electrons trapped at medium depth slowly escape to the conduction band and mainly 1 P0→ 3 F2, 1 P0→ 3 H6 transition, accompanied by 3 P0→ 3 H4 transition, in which electrons undergo simultaneous cross relaxation 1 D2→ 3 H6 jump, when the number of shallow traps and medium traps is similar, the process can be coordinated and balanced to achieve the blue to white and then warm white afterglow.

[0048] It should be noted that NSGGO in the relevant drawings of the present invention is NaSr2GaGe5O 14 abbreviation; in the figure, 0.25% means 2.5 μmol, 0.5% means 5 μmol, and 5.0% means 50 μmol; PDF#49-0273 in the figure is the standard card for XRD.

[0049] The embodiments of the present application are described above in conjunction with the accompanying drawings. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the core idea of ​​the present application, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present application, ordinary technicians in this field can also make many forms without departing from the scope of protection of the purpose of the present application and the claims, all of which are within the protection of the present application.

Claims

1. A white long afterglow luminescent material, characterized in that: The molecular formula of the white long afterglow luminescent material is NaSr2GaGe5O 14 :Pr 3+ , where Pr 3+ As activator, NaSr2GaGe5O 14 As the matrix.

2. The white long afterglow luminescent material according to claim 1, characterized in that The NaSr2GaGe5O 14 :Pr 3+ The Pr content is 2.4%.

3. The method for preparing the white long afterglow luminescent material according to claim 1, characterized in that: The following steps are involved: Anhydrous sodium carbonate, strontium carbonate, germanium oxide, gallium oxide, and praseodymium oxide were used as raw materials, placed in a mortar, added with anhydrous ethanol, mixed and ground for the first time, calcined for the first time after grinding, and cooled to room temperature to obtain a sample powder; The sample powder is ground for a second time, and then calcined for a second time after the grinding is completed. After the calcination is completed, the sample powder is cooled to room temperature. After the cooling is completed, the sample powder is ground for a third time to obtain the white long afterglow luminescent material.

4. The preparation method according to claim 3, characterized in that The usage ratio of the anhydrous sodium carbonate, strontium carbonate, germanium oxide, gallium oxide, praseodymium oxide and anhydrous ethanol is 0.25 mmol: 0.98 mmol: 0.25 mmol: 2.5 mmol: 0.42 μmol-8.3 μmol: 10 mL.

5. The preparation method according to claim 4, characterized in that The usage ratio of the anhydrous sodium carbonate, strontium carbonate, germanium oxide, gallium oxide, praseodymium oxide and anhydrous ethanol is 0.25 mmol: 0.98 mmol: 0.25 mmol: 2.5 mmol: 3.3 μmol: 10 mL.

6. The preparation method according to claim 3, characterized in that The temperature of the first calcination is 450°C-550°C; the temperature of the second calcination is 950°C-1050°C.

7. The preparation method according to claim 6, characterized in that The temperature of the first calcination is 550°C.

8. The preparation method according to claim 7, characterized in that The calcination temperature is 1025°C.

9. The preparation method according to claim 3, characterized in that The time for the first grinding, the second grinding and the third grinding is 25 min-35 min.

10. Use of the white long afterglow luminescent material according to claim 1 in the preparation of white long afterglow luminescent products.

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