A cerium ion doped germanate glass-ceramic containing lithium fluoride nanocrystals and a preparation method thereof

Abstract

The application discloses cerium ion doped germanate glass ceramics containing lithium fluoride nanocrystals and a preparation method thereof, and belongs to the inorganic luminescence field. First, GeO2, LiF, Li2CO3, H3BO3, YF3, La2O3 and CeO2 are used as raw materials, and are uniformly mixed according to a certain stoichiometric ratio, and then the raw materials are put into a reducing atmosphere and high-temperature melted to obtain a precursor glass. Then, the precursor glass is heat-treated to obtain the germanate glass ceramics containing lithium fluoride nanocrystals. Under the excitation of ultraviolet light, the precursor glass and the glass ceramics both present blue light emission of 410 nm. The germanate glass ceramics is simple to prepare, and the light emission intensity is significantly improved compared with the precursor glass. The germanate glass ceramics can be used for preparing a volume Bragg grating (VBG) based on a photo-thermal refractive (PTR) glass, and is further applied to laser system design, three-dimensional display and imaging and optical communication and the like.

Description

Technical Field

[0001] This invention belongs to the field of inorganic luminescent materials and relates to a germanate microcrystalline glass doped with cerium ions and containing lithium fluoride nanocrystals. Background Technology

[0002] Scintillators are luminescent materials that can absorb the energy of high-energy particles (neutrons) in a short time and convert the absorbed ionization energy into ultraviolet or visible light, playing an important role in the field of radiation detection. Glass scintillators, in particular, possess unique advantages such as low manufacturing cost, simple fabrication process, and ease of mass production and large-scale fabrication, effectively compensating for the shortcomings of scintillator crystals in this regard. Meanwhile, microcrystalline glass, as a novel optical material, combines the excellent optical properties of crystalline materials with the advantages of glass materials, such as simple fabrication, low cost, and stable performance.

[0003] Cerium ions, the luminescent centers, exist in both trivalent and tetravalent states. During high-temperature preparation, trivalent cerium ions are readily oxidized to non-luminescent tetravalent cerium ions, resulting in excessively low doping concentrations and weak luminescence. Therefore, reducing tetravalent cerium ions back to trivalent cerium ions as much as possible has become a hot topic in cerium luminescence research. Generally, reducing gases such as CO can effectively reduce and protect trivalent cerium ions. Furthermore, the luminescence intensity of trivalent cerium can be further enhanced by precipitating crystals inside the glass through heat treatment.

[0004] Achieving thermal neutron detection requires using isotopes such as Li-6 as target nuclides to capture neutrons injected into a scintillator. Therefore, developing a germanate microcrystalline glass capable of precipitating lithium-containing crystals is of great significance for the practical application of thermal neutron detection.

[0005] Furthermore, germanate glass crystals with deposited lithium fluoride nanocrystals can be used as photothermal refractive (PTR) glass to fabricate Bragg gratings, effectively locking the output wavelength of high-power semiconductor lasers and narrowing their output linewidth to achieve narrow-linewidth laser output. It can also be applied to 3D displays and imaging, as well as optical communications. Therefore, the development of germanate glass crystals with deposited lithium fluoride nanocrystals is of great significance and has promising application prospects. Summary of the Invention

[0006] To address the aforementioned technical problems in the prior art, this invention provides a cerium-doped lithium fluoride nanocrystal glass and its preparation method. Specifically, the method involves designing the glass composition, obtaining a precursor glass through melt quenching, and then heat-treating the precursor glass to precipitate lithium fluoride nanocrystals within the glass. These nanocrystals emit a Ce-like emission under 350 nm ultraviolet light. 3+ Blue light from the 4f-5d transition.

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

[0008] A cerium ion-doped germanate microcrystalline glass containing lithium fluoride nanocrystals is prepared by using lithium germanate glass as a precursor glass and then precipitating lithium fluoride nanocrystals in the glass through heat treatment.

[0009] With Ce 3+ As a luminescent center, it enters the lithium fluoride crystal to enhance the luminescence intensity of cerium ions.

[0010] Furthermore, in order to improve Ce 3+ The doping concentration was adjusted by using CeO2 as a raw material and obtaining a CO reduction environment in a crucible containing carbon powder, thereby reducing the CeO2 concentration. 4+ Restored to Ce 3+ Ce 3+ The optimal doping concentration was increased to 0.8 mol.

[0011] Furthermore, the thermodynamic properties of the glass were analyzed by differential thermal analysis to determine its crystallization temperature. Heat treatment was then performed near the crystallization temperature for an appropriate crystallization time to obtain cerium ion-doped lithium fluoride nanocrystal glass.

[0012] A method for preparing a cerium ion-doped lithium fluoride nanocrystal glass comprises the following steps:

[0013] (1) Ingredients: Weigh out the raw materials GeO2 (40-50%), LiF (10-15%), Li2CO3 (5-10%), H3BO3 (10-20%), YF3 (5-10%), La2O3 (10-15%) and CeO2 (0.2-1%) according to the molar percentage. The total mass is 10-20 grams. Grind them in an agate mortar for 20-40 minutes to ensure that all raw materials are fully mixed.

[0014] (2) Melting: Pour the evenly mixed raw materials into a 30 ml alumina crucible, then put it into a 500 ml crucible containing carbon powder, and then put it into a lifting furnace at 1450-1500℃ to melt for 1-2 hours.

[0015] (3) Forming annealing: Pour the molten glass into a mold preheated to 400°C and quench it to obtain block glass, and then quickly transfer it to a muffle furnace at 600-700°C for annealing for 6-8 hours.

[0016] (4) Heat treatment: The annealed base glass is heat-treated in a muffle furnace at 750-800℃ for 2-4 hours. After cooling, a cerium ion-doped lithium fluoride nanocrystal microcrystalline glass scintillator can be obtained.

[0017] The cerium ion-doped lithium fluoride nanocrystal glass scintillator of the present invention precipitates lithium fluoride crystals in the glass through heat treatment. 3+ The lithium fluoride crystals deposited inside the glass enable the microcrystalline glass to emit blue light when excited by 350 nm ultraviolet light, and the luminescence intensity increases with increasing particle size. The main innovations are as follows: First, a high-temperature heat treatment technique is used to precipitate lithium fluoride crystals in lithium germanate glass for use in scintillators; second, the preparation method of this microcrystalline glass is simple, does not require a harsh crystal growth environment, and can be mass-produced. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is the emission spectrum of the precursor glass in Example 1 under 350 nm ultraviolet light excitation;

[0020] Figure 2 It is 0.8 mol%Ce in Example 1 3+ Differential thermal analysis diagram of doped precursor glass;

[0021] Figure 3 These are the XRD patterns of the precursor glass in Example 1 and the microcrystalline glass in Examples 2-4;

[0022] Figure 4 This is a high-resolution transmission electron microscope image of Example 4;

[0023] Figure 5 The transmission spectra of the precursor glass in Example 1 and the microcrystalline glass in Examples 2-4 are in the 200-700 nm wavelength range.

[0024] Figure 6 These are the emission spectra of the precursor glass in Example 1 and the microcrystalline glass in Examples 2-4 under 350 nm ultraviolet light excitation;

[0025] Figure 7 The graphs show the fluorescence lifetime of the precursor glass in Example 1 and the microcrystalline glass in Example 4. Detailed Implementation

[0026] The patent will now be further described with reference to the accompanying drawings. Example 1:

[0027] Preparation of basic glass:

[0028] First, according to the molar composition: 45GeO2-12LiF-8Li2O-15B2O3-6YF3-14La2O3, doped with (0.2~0.4)Ce2O3, a total of 15 grams of raw materials were weighed and ground in an agate mortar for 30 minutes to ensure thorough mixing. The mixed materials were then poured into a 30 ml high-purity alumina crucible, which was then placed in a 500 ml crucible containing carbon powder. Both crucibles were then placed in a furnace at 1500℃ for melting for 1 hour. After melting, the molten glass was poured into a preheated mold at 400℃ and quenched to obtain block glass. This block glass was then quickly transferred to a muffle furnace at 600℃ for annealing for 7 hours. After annealing to eliminate internal stress, the glass was cut and polished to a thickness of 2 mm for performance testing. Example 2:

[0029] Preparation of microcrystalline glass

[0030] Based on implementation method 1, using cerium ion-doped glass with a concentration of 0.8 mol% as the base glass, and then according to... Figure 2 The differential thermal analysis diagram shows that the crystallization temperature is 770℃ and the crystallization time is 2h. Based on this time and temperature, heat treatment is carried out in a muffle furnace to obtain a cerium ion-doped lithium fluoride nanocrystal glass. Example 3:

[0031] Preparation of glass-ceramics:

[0032] The steps are the same as in Example 2, except that the crystallization time is changed to 3 hours. Example 4:

[0033] Preparation of glass-ceramics:

[0034] The steps are the same as in Example 2, except that the crystallization temperature is changed to 780℃ and the crystallization time is changed to 3h.

[0035] The properties of the materials prepared in Examples 1-4 were tested:

[0036] In this invention, the emission spectra of lithium germanate glasses doped with different concentrations of cerium ions under 350 nm photoexcitation are as follows: Figure 1 As shown, broadband emission exhibited by the transition between the 4f and 5d energy levels of trivalent cerium ions can be observed. The luminescence intensity increases with increasing cerium ion doping concentration until concentration quenching occurs at 1.0 mol%. Therefore, 0.8 mol% cerium ion concentration is the optimal doping concentration, and glasses doped at this concentration will be used as precursor glasses. Subsequently, thermodynamic properties of the precursor glass doped at this concentration were tested, and the results are as follows: Figure 2The differential thermal analysis diagram shown can reveal the glass softening temperature and crystallization peak temperature, which is helpful for subsequent heat treatment.

[0037] After heat treatment of the precursor glass, a cerium ion-doped lithium fluoride nanocrystal glass can be obtained. The XRD of this glass crystal is as follows: Figure 3 As shown, the lithium fluoride crystals precipitated in the glass are a pure phase, and the grain size increases with increasing crystallization time and temperature. Transmission electron microscopy (TEM) analysis was performed on the microcrystalline glass of Example 4 with the largest grains, yielding the following results: Figure 4 The transmission electron microscope image shown shows the lattice fringes of the lithium fluoride crystal. Calculations show that the lattice fringes spacing is 0.2545 nanometers, which corresponds to the (200) crystal plane of the lithium fluoride crystal. This also proves that pure lithium fluoride crystals have been generated inside the glass. Figure 5 The transmittance of the base glass and the glass-ceramic in the 200-700 nm wavelength range is shown. Both the precursor glass and the glass-ceramic exhibit good transmittance; even Example 4, with the lowest transmittance, is above 60%, which is beneficial for scintillating light output. Furthermore, it can be concluded that the transmittance of the glass-ceramic is inversely proportional to the grain size; the larger the grain size, the lower the transmittance. The emission spectra of the base glass and the glass-ceramic under 350 nm light excitation are shown below. Figure 6 As shown, it can be concluded that the luminescence intensity of the microcrystalline glass is directly proportional to the grain size. The larger the grain, the higher the luminescence intensity. Calculations show that the luminescence intensity of the microcrystalline glass in Examples 2, 3, and 4 is 1.3 times, 1.75 times, and 2 times that of the precursor glass in Example 1, respectively, indicating a significant improvement in luminescence compared to the precursor glass. Figure 7 The fluorescence lifetimes of the precursor glass sample (Example 1) and the microcrystalline glass sample (Example 4) were 17.56 ns and 21.27 ns, respectively. These nanosecond-level fluorescence lifetimes are beneficial for the detection of thermal neutrons.

Claims

1. A cerium ion-doped germanate microcrystalline glass containing lithium fluoride nanocrystals, characterized in that, The molar percentage composition of this germanate microcrystalline glass component is as follows: Molar percentage of raw materials (mol%) GeO2 40~50% LiF 10~15% Li2CO3 5~10% H3BO3 10~20% YF3 5~10% La2O3 10~15% Doping CeO2 0.2~1%。 2. The germanate microcrystalline glass doped with cerium ions and containing lithium fluoride nanocrystals according to claim 1, characterized in that, The crystals precipitated in the germanate microcrystalline glass are cubic lithium fluoride crystals.

3. The germanate microcrystalline glass doped with cerium ions and containing lithium fluoride nanocrystals according to claim 2, characterized in that, The precipitated lithium fluoride crystals have a particle size of 0.1~100 nm.

4. The germanate microcrystalline glass doped with cerium ions and containing lithium fluoride nanocrystals according to claim 3, characterized in that, The germanate microcrystalline glass doped with Ce 3+ As a luminescent center, it enters the lithium fluoride crystal, and its luminescence intensity increases with the increase of the crystal size.

5. The germanate microcrystalline glass doped with cerium ions and containing lithium fluoride nanocrystals according to claim 4, characterized in that, It emits a emission corresponding to Ce under ultraviolet light excitation at 350 nm. 3+ Blue light from the 4f-5d transition.

6. A method for preparing cerium ion-doped lithium fluoride nanocrystal germanate glass as described in any one of claims 1-5, characterized in that... Includes the following steps: (1) Ingredients: Weigh out 10-20 grams of raw materials according to the glass raw material composition and molar percentage, and grind them in an agate mortar for 20-40 minutes to ensure that all raw materials are fully mixed. (2) Melting: Pour the evenly mixed raw materials into a 30 ml high-purity alumina crucible or platinum crucible, then put it into a 500 ml crucible containing carbon powder or pass N2-H2 mixed gas through it, or add reducing raw materials such as Si3N4 and AlN to the raw materials, and then put it into a high-temperature furnace at 1450-1500℃ to melt for 1-2 hours. (3) Molding annealing: Pour the molten glass into a mold preheated to 400°C and press it with another stainless steel plate to cool and shape it quickly to obtain a block precursor glass. Then quickly transfer it to a muffle furnace at 600-700°C for annealing for 6-8 hours. (4) Heat treatment: The annealed precursor glass is heat-treated in a muffle furnace at 750-800℃ for 0.5-6 hours, and after cooling, the cerium ion-doped lithium fluoride nanocrystal germanate microcrystalline glass can be obtained.

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