Cerium ion doped germanate microcrystalline glass containing lithium fluoride nanocrystalline and preparation method thereof

Abstract

The invention discloses a cerium ion doped germanate microcrystalline glass containing lithium fluoride nanocrystalline and a preparation method thereof, and belongs to the field of inorganic luminescence. The preparation method comprises the following steps: firstly, taking GeO2, LiF, Li2CO3, H3BO3, YF3, La2O3 and CeO2 as raw materials, uniformly mixing according to a certain stoichiometric ratio, putting the mixture into a reducing atmosphere, and melting at a high temperature to obtain precursor glass; and then carrying out heat treatment on the precursor glass to obtain the germanate microcrystalline glass containing the lithium fluoride nanocrystals. Under the excitation of ultraviolet light, both the precursor glass and the microcrystalline glass emit blue light of 410 nm. The germanate microcrystalline glass is simple to prepare, and the luminous intensity is obviously improved compared with that of precursor glass. The method can be used for preparing a volume bragg grating (VBG) based on photo-thermo-sensitive refraction (PTR) glass, and is further applied to the aspects of laser system design, three-dimensional display and imaging, optical communication and the like.

Description

Technical Field

[0001] The invention belongs to the field of inorganic luminescent materials and relates to cerium ion-doped germanate glass-ceramics containing lithium fluoride nanocrystals. Background Art

[0002] Scintillator is a luminescent material that can absorb the energy of high-energy particles (neutrons) in a short period of time and convert the absorbed ionization energy into ultraviolet or visible light. It plays an important role in the field of radiation detection. Glass scintillator has unique advantages in terms of low preparation cost, simple preparation process, and easy large-scale and large-size preparation, which effectively makes up for the shortcomings of scintillating crystals in this regard. As a new type of optical material, microcrystalline glass has the advantages of both the excellent optical properties of crystal materials and the advantages of glass materials such as easy preparation, low cost, and stable performance.

[0003] Cerium ions, which are the luminescence centers, exist in two valence states: trivalent and tetravalent. During the high-temperature preparation process, trivalent cerium ions are easily oxidized into non-luminescent tetravalent cerium ions, resulting in too low doping concentration and weak luminescence. How to reduce tetravalent cerium ions to trivalent cerium ions as much as possible has become a hot topic in the study of cerium luminescence. Generally speaking, trivalent cerium ions can be effectively reduced and protected by reducing gases such as CO. On this basis, the luminescence intensity of trivalent cerium can be further improved by heat treatment to precipitate crystals inside the glass.

[0004] Thermal neutron detection requires the use of isotopes such as Li-6 as target nuclides to capture neutrons incident on the scintillator. Therefore, the development of a germanate glass-ceramic that can precipitate lithium-containing crystals is very meaningful for the practical application of thermal neutron detection.

[0005] In addition, germanate glass-ceramics with lithium fluoride nanocrystals can be used as photothermal refractive (PTR) glass to prepare Bragg gratings, which can effectively lock the output wavelength of high-power semiconductor lasers and narrow their output line width to successfully achieve narrow line width laser output. It can also be used in three-dimensional display and imaging, as well as optical communications. Therefore, the development of germanate glass-ceramics with lithium fluoride nanocrystals is of great significance and application prospects. Summary of the invention

[0006] In order to solve the above technical problems existing in the prior art, the present invention provides a cerium ion doped glass-ceramic containing lithium fluoride nanocrystals and a preparation method thereof, specifically, by designing the glass components, obtaining a precursor glass by a melt quenching method, and then heat treating the precursor glass, thereby precipitating lithium fluoride nanocrystals in the glass. 3+ : The blue light of the 4f-5d transition.

[0007] To achieve the above object, the present invention provides the following technical solutions: A cerium ion doped germanate glass-ceramic containing lithium fluoride nanocrystals uses lithium germanate glass as a precursor glass and then precipitates lithium fluoride nanocrystals in the glass through heat treatment.

[0008] Ce 3+ As a luminescence center, it enters the lithium fluoride crystal to enhance the luminescence intensity of the cerium ion.

[0009] Furthermore, in order to improve Ce 3+ The doping concentration of CeO 2 As a raw material, a CO reducing environment was obtained in a crucible filled with carbon powder to convert Ce 4+ Reduction to Ce 3+ , Ce 3+ The optimal doping concentration was increased to 0.8 mol%.

[0010] Furthermore, the thermodynamic properties of the glass are analyzed by differential thermal curves to determine its crystallization temperature, and heat treatment is performed near the crystallization temperature for a suitable crystallization time to obtain cerium ion-doped microcrystalline glass containing lithium fluoride nanocrystals.

[0011] A method for preparing cerium ion-doped glass-ceramics containing lithium fluoride nanocrystals comprises the following steps in sequence: (1) Ingredients: Weigh the raw material GeO according to molar percentage. 2 (40~50%), LiF (10~15%), Li 2 CO 3 (5~10%), H 3 BO 3 (10~20%), YF 3 (5~10%), La 2 O 3 (10~15%) and CeO 2 (0.2-1%), with a total mass of 10-20 g, and ground in an agate mortar for 20-40 minutes to fully mix the various raw materials; (2) Melting: Pour the uniformly mixed raw materials into a 30 ml alumina crucible, then put it into a 500 ml large crucible filled with carbon powder, and then put it into a lifting furnace at 1450-1500° C. to melt for 1-2 hours; (3) Forming annealing: Pour the molten glass into a mold preheated at 400°C and quench to obtain block glass, which is then quickly transferred to a muffle furnace at 600-700°C and annealed for 6-8 hours.

[0012] (4) Heat treatment: The annealed base glass is heat treated in a muffle furnace at 750-800° C. for 2-4 hours, and after cooling, a cerium ion-doped glass-ceramic scintillator containing lithium fluoride nanocrystals is obtained.

[0013] The cerium ion doped glass-ceramic scintillator containing lithium fluoride nanocrystals of the present invention is heat treated to precipitate lithium fluoride crystals in the glass. 3+ The lithium fluoride crystals that enter the glass make the microcrystalline glass emit blue light under the excitation of 350-nanometer ultraviolet light, and the luminescence intensity increases with the increase of particle size. The main innovations are as follows: First, lithium fluoride crystals are precipitated in lithium germanate glass by high-temperature heat treatment technology and used in the field of scintillators; second, the preparation method of this microcrystalline glass is simple, does not require a strict crystal growth environment, and can be prepared in large quantities. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. 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 creative work.

[0015] Figure 1 is the emission spectrum of the precursor glass in Example 1 under 350 nm ultraviolet light excitation; Figure 2 0.8 mol% Ce in Example 1 3+ Differential thermal analysis of doped precursor glass; Figure 3 is the XRD diagram of the precursor glass in Example 1 and the glass-ceramics in Examples 2 to 4; Figure 4 is a high-definition transmission electron microscope image of Example 4; Figure 5 is the transmission spectrum of the precursor glass in Example 1 and the glass-ceramics in Examples 2 to 4 in the 200-700 nm band; Figure 6 is the emission spectrum of the precursor glass in Example 1 and the glass-ceramics in Examples 2 to 4 under 350 nm ultraviolet light excitation; Figure 7 It is the fluorescence lifetime diagram of the precursor glass in Example 1 and the microcrystalline glass in Example 4. DETAILED DESCRIPTION

[0016] The present patent is further described below in conjunction with the accompanying drawings. Embodiment 1:

[0017] Preparation of base glass: First, according to the molar composition: 45GeO 2 -12LiF-8Li 2 O-15B 2 O 3 -6YF 3 -14La 2 O 3 , doped with (0.2~0.4) Ce 2 O 3 , Weigh a total of 15 grams of raw materials and grind them in an agate mortar for 30 minutes to fully mix the various raw materials. Then pour the mixed raw materials into a 30 ml high-purity alumina crucible, and then put them into a 500 ml large crucible filled with carbon powder, and then put them into a 1500°C lifting furnace to melt for 1 hour. After the melting is completed, pour the glass liquid into a mold preheated at 400°C to quench and obtain block glass, and quickly transfer it to a muffle furnace at 600°C for annealing for 7 hours. After the annealing is completed and the stress inside the glass is eliminated, the glass is cut and polished to a thickness of 2 mm for performance testing. Embodiment 2:

[0018] Preparation of glass-ceramics On the basis of Example 1, 0.8 mol% cerium ion doped glass is used as the base glass, and then according to Figure 2 From the differential thermal analysis diagram in the figure, it is determined that the crystallization temperature is 770℃ and the crystallization time is 2h. By heat treating in a muffle furnace according to this time and temperature, a piece of cerium ion-doped microcrystalline glass containing lithium fluoride nanocrystals can be obtained. Embodiment 3:

[0019] Preparation of glass-ceramics: The steps are the same as in Example 2, except that the crystallization time is changed to 3 h. Embodiment 4:

[0020] Preparation of glass-ceramics: The steps are the same as those in Example 2, except that the crystallization temperature is changed to 780° C. and the crystallization time is changed to 3 h.

[0021] The performance tests were performed on the materials prepared in Examples 1 to 4: In the present invention, the emission spectra of lithium germanate glasses doped with different concentrations of cerium ions under 350 nm light excitation are as follows: Figure 1As shown in the figure, broadband emission can be observed from the transition between the 4f and 5d energy levels of trivalent cerium ions, and the luminescence intensity increases with the increase of the cerium ion doping concentration until the concentration reaches 1.0 mol%, where concentration quenching occurs. Therefore, 0.8 mol% cerium ion concentration is the optimal doping concentration, and the glass doped with this concentration will be used as the precursor glass in the future. Subsequently, the thermodynamic properties of the precursor glass doped with this concentration were tested, and the following results were obtained: Figure 2 The differential thermal analysis diagram shown can reveal the glass softening temperature and crystallization peak temperature, which is convenient for subsequent heat treatment.

[0022] After heat treatment of the precursor glass, a cerium ion-doped glass-ceramic containing lithium fluoride nanocrystals can be obtained. The XRD characteristics of the glass-ceramic are as follows: Figure 3 As shown, it can be concluded that the lithium fluoride crystals precipitated in the glass are pure phases, and the grain size increases with the increase of crystallization time and crystallization temperature. The transmission electron microscope test of the microcrystalline glass of Example 4 with the largest grains shows the following: Figure 4 In the transmission electron microscope image shown, the lattice fringes of lithium fluoride crystals can be observed. Calculation shows that the spacing between the lattice fringes 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 grown inside the glass. Figure 5 The transmittance of the base glass and the microcrystalline glass in the 200-700 nanometer band is shown. Both the precursor glass and the microcrystalline glass have good transmittance. The transmittance of Example 4, which has the lowest transmittance, is also higher than 60%, which is conducive to the output of the flashing light. It can also be concluded that the transmittance of the microcrystalline glass is inversely proportional to the grain size. The larger the grain of the microcrystalline glass, the lower its transmittance. The emission spectra of the base glass and the microcrystalline glass under 350nm light excitation are shown in Figure 2. Figure 6 As shown, it can be concluded that the luminescence intensity of the microcrystalline glass is proportional to the grain size. The larger the grain, the higher its luminescence intensity. Calculation shows that the luminescence intensity of the microcrystalline glass of Examples 2, 3, and 4 are 1.3 times, 1.75 times, and 2 times that of the precursor glass of Example 1, respectively. The luminescence is significantly improved compared to the precursor glass. Figure 7 The fluorescence lifetimes of the samples of precursor glass example 1 and microcrystalline glass example 4 are 17.56 ns and 21.27 ns, respectively. The fluorescence lifetimes are in the nanosecond level, which is conducive to the detection of thermal neutrons.

Claims

1. A cerium ion doped germanate glass-ceramics containing lithium fluoride nanocrystals, characterized in that: The molar percentage composition of the germanate glass-ceramics components is: Raw material molar percentage (mol%) GeO240~50% LiF 10~15% Li2CO35~10% H3BO310~20% YF35~10% La2O310~15% Doping CeO20.2~1%.

2. The cerium ion-doped germanate glass-ceramics containing lithium fluoride nanocrystals according to claim 1, characterized in that: The crystals precipitated from the germanate glass-ceramics are cubic lithium fluoride crystals.

3. The cerium ion-doped germanate glass-ceramics containing lithium fluoride nanocrystals according to claim 2, characterized in that: The particle size of the precipitated lithium fluoride crystals is 0.1~100 nm.

4. The cerium ion-doped germanate glass-ceramics containing lithium fluoride nanocrystals according to claim 3, characterized in that: The Ce doped in the germanate glass-ceramics 3+ It enters the lithium fluoride crystal as a luminescence center, and its luminescence intensity becomes stronger as the grain size increases.

5. The cerium ion-doped germanate glass-ceramics containing lithium fluoride nanocrystals according to claim 4, characterized in that: Under 350 nm ultraviolet light excitation, it emits a 3+ : The blue light of the 4f-5d transition.

6. A method for preparing cerium ion-doped germanate glass-ceramics containing lithium fluoride nanocrystals as claimed in any one of claims 1 to 5, characterized in that The steps include: (1) Ingredients: According to the glass raw material components and molar percentages, weigh a total of 10-20 grams of raw materials, and grind them in an agate mortar for 20-40 minutes to fully mix the various raw materials; (2) Melting: Pour the mixed raw materials into a 30 ml high-purity alumina crucible or platinum crucible, then place it into a 500 ml large crucible filled with carbon powder or pass N2-H2 mixed gas, or add reducing raw materials such as Si3N4 and AlN to the raw materials, and then place it into a high-temperature furnace at 1450-1500°C for melting for 1-2 hours; (3) Forming annealing: Pour the molten glass into a mold preheated at 400°C and press it with another stainless steel plate to quickly cool and form a bulk precursor glass, which is then quickly transferred to a muffle furnace at 600-700°C for annealing for 6-8 hours; (4) Heat treatment: heat treating the annealed precursor glass in a muffle furnace at 750-800° C. for 0.5-6 hours, and then cooling the precursor glass to obtain the cerium ion-doped germanate glass-ceramics containing lithium fluoride nanocrystals.

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