Rare earth Ho < 3 + > doped Bi2YbO4Cl fluorescent powder material as well as preparation method and application thereof

Abstract

The invention discloses a rare earth Ho < 3 + > doped Bi2YbO4Cl fluorescent powder material as well as a preparation method and application thereof, and belongs to the technical field of luminescent materials. The general chemical formula of the fluorescent powder material is Bi2Yb (1-x) O4Cl: xHo, wherein x is more than or equal to 0.02 and less than or equal to 0.20. Under the excitation of 980nm exciting light, the material shows the characteristic of rapid temperature rise, and can reach and maintain a stable temperature in a short time, the light emission in a visible light region is weakened along with the temperature rise, and the near infrared light emission near 855nm is enhanced; in addition, the fluorescence color of the material shows a positive response characteristic to excitation power and time, and the up-conversion luminescence intensity shows a negative response relation. The material is prepared by adopting a one-step calcination method, is simple and convenient in process, low in cost and suitable for large-scale production, has excellent fluorescence color modulation performance based on 980nm excitation, and can be used for a novel dynamic fluorescence anti-counterfeiting technology.

Description

Technical Field

[0001] This invention relates to a rare earth Ho 3+ The doped Bi₂YbO₄Cl phosphor material, its preparation method and application belong to the field of luminescent material technology. Background Technology

[0002] Among existing optical anti-counterfeiting technologies, photoluminescent materials, especially upconversion luminescent materials, have become a research hotspot in the field of information encryption and anti-counterfeiting due to their simple design, high visual sensitivity, and ability to produce rich emission colors through rare earth ion doping. Currently, most of these widely used materials are static fluorescent materials, whose core characteristic is that under a fixed set of excitation conditions (such as near-infrared lasers of specific wavelengths and powers), the material emits fluorescence of a fixed color and intensity. This "one-to-one" static response mode, while achieving basic anti-counterfeiting functions to a certain extent, has a single and unchanging form of expression, limiting its practical application. Traditional static fluorescent materials are no longer sufficient to meet the needs of high-end anti-counterfeiting applications.

[0003] Static fluorescent materials face significant technical bottlenecks. Because their fluorescence signals are fixed, they are easily replicated and counterfeited by modern high-precision spectroscopic equipment and color copying technology, resulting in limited anti-counterfeiting security. More importantly, this static characteristic makes it impossible to exhibit advanced anti-counterfeiting features such as dynamic color gradations and pattern transitions, and it is also difficult to carry multi-dimensional information. Therefore, developing a material capable of generating dynamic and tunable fluorescence responses to external stimuli has become a crucial technical problem urgently needing to be solved in this field. Summary of the Invention

[0004] To address the problem of static fluorescent materials exhibiting limited and monotonous morphology, the present invention aims to provide a rare-earth Ho... 3+ A Bi₂YbO₄Cl doped phosphor material, wherein the chemical formula of the phosphor material is: Bi₂Yb (1-x) O4Cl:xHo, 0.02≤x≤0.20.

[0005] Another objective of this invention is to provide a method for preparing rare earth Ho-doped Bi₂YbO₄Cl phosphor materials, specifically including the following steps: (1) Mix and grind Bi2O3, Yb2O3, NH4Cl and Ho2O3 evenly to obtain a mixed powder.

[0006] (2) The mixed powder was calcined and cooled to obtain rare earth Ho-doped Bi2YbO4Cl phosphor material.

[0007] Preferably, the mixing and grinding conditions in step (1) of the present invention are: adding anhydrous ethanol and grinding for 30 to 40 minutes.

[0008] Preferably, the calcination conditions in step (2) of the present invention are: calcination at 800~850℃ for 12~16 hours, with a heating rate of 4~7℃ / min.

[0009] Another object of the present invention is to provide a rare earth Ho 3+ Application of Bi₂YbO₄Cl doped phosphor material in dynamic fluorescent anti-counterfeiting.

[0010] Mechanism of the invention: This material, through its unique layered structure and low phonon energy environment, enables Yb 3+ / Ho 3+ The luminescent center is confined within it, and under 980nm laser excitation, Yb 3+ Absorb energy and efficiently transfer it to Ho 3+ This achieves upconversion luminescence; due to Ho 3+ Located in a centrosymmetric lattice field (P4 / mmm space group), its green light emission is temperature-sensitive, while its red light emission is relatively stable. Continuous laser irradiation causes the material to heat up, and the green light weakens rapidly due to thermal quenching, and the emission color gradually changes from green to red. After the laser is turned off, the material cools down, and the emission returns to the initial green color. This reversible ratio color change process originates from the different thermal response characteristics of green light and red light.

[0011] Compared with the prior art, the present invention provides a rare earth Ho 3+ The doped Bi₂YbO₄Cl phosphor materials, their preparation methods, and applications have the following beneficial effects: (1) The rare earth Ho prepared by this invention 3+ The phosphor material doped with Bi2YbO4Cl exhibited good fluorescence color-changing properties under 980nm light excitation, indicating that the material prepared by this invention has dynamic fluorescence properties. Therefore, this material has great application potential in the field of optical anti-counterfeiting.

[0012] (2) This invention uses Bi2YbO4Cl as the matrix, through Yb 3+ and Ho 3+ The synergy between these factors allows the luminescent material to undergo cross-relaxation at different energy levels, enabling dynamic control of the particle number distribution in each excited state and thus achieving adjustable emission color.

[0013] (3) The rare earth Ho provided by the present invention 3+ The preparation method of Bi2YbO4Cl-doped phosphor material is mild and simple, and the phosphor provided by this invention has good luminescence properties.

[0014] (4) Rare earth Ho provided by the method described in this invention 3+Bi2YbO4Cl-doped phosphors achieve efficient green upconversion luminescence under 980nm excitation, and then transition to red as the excitation time increases. Based on this, they can be applied to dynamic fluorescent anti-counterfeiting. Attached Figure Description

[0015] Figure 1 The time-resolved emission normalized spectrum and CIE coordinate diagram of Example 4 under 1145mW 980nm laser excitation.

[0016] Figure 2 Examples 1-5 and Comparative Examples 1-3 are based on different rare earth elements (Ho). 3+ X-ray diffraction (XRD) pattern of phosphors prepared under doping.

[0017] Figure 3 The images show the room-temperature fluorescence spectra of the phosphor materials prepared in Examples 1-5 and Comparative Example 1 under 980 nm excitation.

[0018] Figure 4 The normalized emission spectra and CIE coordinate diagrams of Example 4 and Comparative Examples 2-3 after 1 min of excitation by a 980 nm laser at 1145 mW are shown.

[0019] Figure 5 The real-time temperature variation of the phosphors prepared in Example 4 and Comparative Examples 2-3 under 1145mW 980nm light excitation with time is shown.

[0020] Figure 6 This is a dynamic fluorescence image of the phosphor prepared in Example 4 under 1145mW 980nm light excitation. Detailed Implementation

[0021] 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.

[0022] Example 1 Preparation of Bi2Yb (1-x) O4Cl:xHo phosphor, x=0.02, the specific steps are as follows: (1) Weigh Bi2O3, Yb2O3, NH4Cl and Ho2O3 in a molar ratio of 2:0.98:1.25:0.02 and place them in an agate mortar. Add an appropriate amount of anhydrous ethanol (enough to submerge all the weighed solids), mix and grind for 30 minutes to obtain a uniformly mixed powder.

[0023] (2) Pour the well-mixed powder into an alumina crucible, place it in a muffle furnace, heat it to 825°C at a rate of 5°C / min, and calcine it for 16 hours to obtain Bi2Yb. 0.98 O4Cl:0.02Ho phosphor.

[0024] Example 2 Preparation of Bi2Yb (1-x) O4Cl:xHo phosphor, x=0.06, the specific steps are as follows: (1) Weigh Bi2O3, Yb2O3, NH4Cl and Ho2O3 in a molar ratio of 2:0.94:1.25:0.06 and place them in an agate mortar. Add an appropriate amount of anhydrous ethanol (enough to submerge all the weighed solids), mix and grind for 35 minutes to obtain a uniformly mixed powder.

[0025] (2) Pour the well-mixed powder into an alumina crucible, place it in a muffle furnace, heat it to 850°C at a rate of 7°C / min, and calcine it for 14 hours to obtain Bi2Yb. 0.94 O4Cl:0.06Ho phosphor.

[0026] Example 3 Preparation of Bi2Yb (1-x) O4Cl:xHo phosphor, x=0.10, the specific steps are as follows: (1) Weigh Bi2O3, Yb2O3, NH4Cl and Ho2O3 in a molar ratio of 2:0.90:1.25:0.10 and place them in an agate mortar. Add an appropriate amount of anhydrous ethanol (enough to submerge all the weighed solids), mix and grind for 40 minutes to obtain a uniformly mixed powder.

[0027] (2) Pour the well-mixed powder into an alumina crucible, place it in a muffle furnace, heat it to 800°C at a rate of 4°C / min, and calcine it for 12 hours to obtain Bi2Yb. 0.90 O4Cl:0.10Ho phosphor.

[0028] Example 4 Preparation of Bi2Yb (1-x) O4Cl:xHo phosphor, x=0.15, the specific steps are as follows: (1) Weigh Bi2O3, Yb2O3, NH4Cl and Ho2O3 in a molar ratio of 2:0.85:1.25:0.15 and place them in an agate mortar. Add an appropriate amount of anhydrous ethanol (enough to submerge all the weighed solids), mix and grind for 30 minutes to obtain a uniformly mixed powder.

[0029] (2) Pour the well-mixed powder into an alumina crucible, place it in a muffle furnace, heat it to 800°C at a rate of 5°C / min, and calcine it for 12 hours to obtain Bi2Yb. 0.85 O4Cl:0.15Ho phosphor.

[0030] The phosphor prepared in this embodiment was subjected to time-resolved emission spectroscopy under 980 nm light excitation, and the results are as follows. Figure 1 As shown, under 980 nm light excitation at 1145 mW, the material exhibits significant photoluminescence color changes with increasing excitation time, stabilizing after 1 min. The fluorescence color changes are shown in the CIE coordinate diagram. The phosphor prepared in this embodiment was used for anti-counterfeiting applications under 980 nm excitation, and the results are as follows... Figure 6 As shown, under the same excitation mode, samples emit distinctly different colors at different excitation times, which can be applied to dynamic anti-counterfeiting.

[0031] Example 5 Preparation of Bi2Yb (1-x) O4Cl:xHo phosphor, x=0.20, the specific steps are as follows: (1) Weigh Bi2O3, Yb2O3, NH4Cl and Ho2O3 in a molar ratio of 2:0.80:1.25:0.20 and place them in an agate mortar. Add an appropriate amount of anhydrous ethanol (enough to submerge all the weighed solids), mix and grind for 30 minutes to obtain a uniformly mixed powder.

[0032] (2) Pour the well-mixed powder into an alumina crucible, place it in a muffle furnace, heat it to 800°C at a rate of 5°C / min, and calcine it for 12 hours to obtain Bi2Yb. 0.80 O4Cl:0.20Ho phosphor.

[0033] Comparative Example 1 The specific steps for preparing Bi₂YbO₄Cl phosphor are as follows: (1) Weigh Bi2O3, Yb2O3 and NH4Cl in a molar ratio of 2:1:1.25 and place them in an agate mortar. Add an appropriate amount of anhydrous ethanol (enough to submerge all the weighed solids), mix and grind for 30 minutes to obtain a uniformly mixed powder.

[0034] (2) Pour the well-mixed powder into an alumina crucible, place it in a muffle furnace and heat it to 800°C at a rate of 5°C / min, and calcine it for 12 hours to obtain Bi2YbO4Cl phosphor.

[0035] In comparison, this comparative example differs from Example 1 in that it does not contain rare earth element Ho. 3+ .

[0036] Comparative Example 2 Preparation of rare earth Ho 3+ Y 3+ The specific steps for co-doping Bi₂YbO₄Cl phosphors are as follows: (1) Weigh Bi2O3, Yb2O3, Y2O3, NH4C and Ho2O3 in a molar ratio of 2:0.1:0.75:1.25:0.15 and place them in an agate mortar. Add an appropriate amount of anhydrous ethanol (enough to submerge all the weighed solids), mix and grind for 30 minutes to obtain a uniformly mixed powder.

[0037] (2) Pour the well-mixed powder into an alumina crucible, place it in a muffle furnace, heat it to 800°C at a rate of 5°C / min, and calcine it for 12 hours to obtain Bi2Yb. 0.1 Y 0.75 O4Cl:0.15Ho phosphor.

[0038] In comparison, this comparative example differs from Example 4 in that it is doped with rare earth element Y. 3+ Partially replaces Yb 3+ .

[0039] Comparative Example 3 Preparation of rare earth Ho 3+ Y 3+ The specific steps for co-doping Bi₂YbO₄Cl phosphors are as follows: (1) Weigh Bi2O3, Yb2O3, Y2O3, NH4C and Ho2O3 in a molar ratio of 2:0.5:0.35:1.25:0.15 and place them in an agate mortar. Add an appropriate amount of anhydrous ethanol (enough to submerge all the weighed solids), mix and grind for 30 minutes to obtain a uniformly mixed powder.

[0040] (2) Pour the well-mixed powder into an alumina crucible, place it in a muffle furnace, heat it to 800°C at a rate of 5°C / min, and calcine it for 12 hours to obtain Bi2Yb. 0.5 Y 0.35 O4Cl:0.15Ho phosphor.

[0041] In comparison, this comparative example differs from Example 4 in that it is doped with rare earth element Y. 3+ Partially replaces Yb 3+ .

[0042] The materials prepared in Examples 1-5 and Comparative Examples 1-3 were subjected to relevant performance tests. First, X-ray diffraction analysis was performed on the prepared materials, and the results are as follows: Figure 2 As shown in the figure, it can be seen that the synthesized samples with different Ho doping concentrations are all pure phases, and changing the conditions and doping concentration does not affect their phase purity.

[0043] The materials prepared in Examples 1-5 and Comparative Example 1 were subjected to room-temperature spectral analysis under 980 nm excitation. The results are as follows: Figure 3 As shown in the figure, three characteristic emission peaks can be observed near 545nm, 655nm, and 755nm, corresponding to Ho, respectively. 3+ of 5 S2 / 5 F4→ 5 I8 5 F5 → 5 I8 and 5 S2 / 5 F4→ 5 I7 level transition.

[0044] The emission spectra of the materials prepared in Example 4 and Comparative Examples 2-3 were analyzed at 980 nm photoexcitation at 1145 mW. The luminescence properties ( Figure 4 From the perspective of photothermal performance, Example 4 exhibits higher luminescence intensity and superior luminescence characteristics in a specific wavelength region; Figure 5 From the results, the photothermal conversion efficiency of Example 4 is significantly higher than that of Comparative Example 2 and Comparative Example 3, which indicates that the phosphor prepared in Example 4 has better luminescence and photothermal properties.

[0045] In summary, this invention has developed a Ho 3+ The Bi₂YbO₄Cl phosphor material exhibits efficient upconversion luminescence under 980 nm laser excitation. Its luminescence color dynamically changes with laser irradiation time: initially dominated by green light, it gradually transforms into red light as irradiation time increases, and the color recovers after the laser is turned off, demonstrating reversible ratio-dependent color-changing characteristics. The material is prepared under mild conditions, is easy to operate, and has excellent luminescence performance. Based on its dynamic luminescence characteristics, it can be applied in the field of optical anti-counterfeiting.

[0046] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A rare earth Ho 3+ The Bi2YbO4Cl fluorescent powder material is characterized in that: The chemical formula of the fluorescent powder material is: Bi2Yb (1-x) O4Cl:xHo, 0.02≤x≤0.

20.

2. The preparation method of the rare earth Ho-doped Bi2YbO4Cl fluorescent powder material of claim 1, characterized in that, Specifically comprising the following steps: (1) uniformly mixing and grinding Bi2O3, Yb2O3, NH4Cl and Ho2O3 to obtain a mixed powder; (2) calcining the mixed powder and cooling to obtain a rare earth Ho-doped Bi2YbO4Cl fluorescent powder material.

3. The rare earth Ho 3+ The application discloses a preparation method of a Bi2YbO4Cl doped fluorescent powder material. The mixing and grinding condition in step (1) is: adding anhydrous ethanol for grinding for 30-40 minutes.

4. The rare earth Ho 3+ The application discloses a preparation method of a Bi2YbO4Cl doped fluorescent powder material. The calcining condition in step (2) is: calcining at 800-850℃ for 12-16 hours, and the temperature rising rate is 4-7℃ / min.

5. The rare earth Ho of claim 1 3+ Application of Bi2YbO4Cl fluorescent powder material in dynamic fluorescence anti-counterfeiting.

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