A glass-ceramic scintillator and its preparation method and application

Abstract

The present invention belongs to the field of optical functional materials and detection technology, and discloses a method for preparing a microcrystalline glass scintillator and its application in the field of X-ray detection. The specific preparation steps include: S1: accurately weighing SiO2, Na2CO3, Al2O3, CaCO3, NaF, LuF3, and EuF3 raw materials, and fully mixing them; S2: weighing a reducing agent, and adding the reducing agent to the mixture, and transferring it into an alumina crucible after fully mixing; S3: transferring the crucible containing the mixed powder to a high temperature, and keeping it warm until the mixed powder in the crucible becomes a uniform melt; S4: pouring the uniform melt on a mold to obtain a quenched precursor glass I; S5: first annealing the obtained precursor glass to obtain a precursor glass II; S6: transferring the precursor glass II to a muffle furnace for heat preservation to obtain a microcrystalline glass scintillator. The scintillator of the present invention has excellent radiation resistance and is suitable for high-resolution X-ray imaging.

Description

Technical Field

[0001] The present invention relates to the field of photoelectric functional materials and detection technology, specifically a Na 5 Lu 9 F 32 :Application of Eu glass-ceramic scintillator and its preparation method in X-ray detection field. Background Art

[0002] Scintillators can convert high-energy ionizing radiation into ultraviolet and visible light, and have a wide range of applications in medical imaging, industrial nondestructive testing, and safety inspection. Although traditional single crystals such as BGO, CsI:Tl, and YAG:Ce are still the main scintillators for market applications, the shortcomings of such scintillators, such as long preparation cycle, high cost, inflexible device processability, and low resolution, have also become major obstacles to further application. New scintillators, such as perovskite scintillators, are unstable in harsh environments such as high temperature, high humidity, and high-energy x-ray irradiation, as well as the unfavorable factor of lead, which increases the difficulty of production and application. In order to meet the diversification of social functions and the progress of science and technology, scintillators need to be continuously iterated and updated in terms of performance and quality. Therefore, researchers are committed to developing a scintillator that has the advantages of the above materials and overcomes their shortcomings.

[0003] When exposed to ionizing radiation, scintillators have the ability to convert the absorbed radiation energy into visible light or ultraviolet light. The converted visible light and ultraviolet light can be easily detected and measured by detectors (such as photomultiplier tubes or solid-state photodetectors), thereby locating and quantifying the radiation source. In the face of high-energy radiation, the current scintillator technology has the following main defects:

[0004] 1. Preparation cost and cycle: Traditional single crystal scintillators have high preparation costs and long preparation cycles; new scintillators such as perovskite and organic scintillators have complex preparation processes and high costs, which hinders large-scale application and promotion.

[0005] 2. Stability: New scintillators are generally not stable enough in extreme environments (high temperature, high humidity and high-energy x-ray irradiation), and their application life is greatly reduced.

[0006] 3. Environmental protection: New scintillators such as perovskite contain lead and are unstable. This is a harmful heavy metal that affects the environment and human health. Therefore, it is necessary to find alternative materials that do not contain lead or have a low lead content.

[0007] 4. Performance parameters: Traditional crystals will induce excessive electron-hole migration when irradiated by X-rays, causing radiation afterglow. Radiation afterglow will cause imaging ghosting and affect resolution. High stability, high spatial resolution, excellent radiation luminescence, and reasonable decay time are the basic requirements for scintillator performance, and current scintillators cannot meet these requirements well.

[0008] Therefore, researchers need to develop a scintillator that has the advantages of the above materials while overcoming their disadvantages in order to meet the higher requirements of scintillators brought about by the continuous progress of society and science. Summary of the invention

[0009] In view of the problems and shortcomings in the prior art, the present invention provides a Na 5 Lu 9 F 32 :Eu glass-ceramic scintillator, preparation method and its application in X-ray detection field.

[0010] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0011] A glass-ceramic scintillator with silicate glass as the matrix and Na 5 Lu 9 F 32 :Eu nanocrystals are the luminescence centers.

[0012] Furthermore, the molar ratios of the glass components of the microcrystalline glass scintillator are: SiO 2 :36-56mol%Na 2 CO 3 :6-16mol%Al 2 O 3 : 9-21 mol%CaCO 3 :3-8mol%, NaF: 3-10mol%, LuF 3 : 4-15mol%,EuF 3 : 0-3 mol%.

[0013] The present invention also provides a method for preparing a glass-ceramic scintillator, comprising the following steps:

[0014] (1) Accurately weigh SiO 2 , Na 2 CO 3 , Al 2 O 3 , CaCO 3 , NaF, LuF 3 ,EuF 3 Raw materials and mix thoroughly;

[0015] (2) weighing a reducing agent and adding the reducing agent to the mixture in step (1), mixing thoroughly and transferring the mixture into an alumina crucible;

[0016] (3) transferring the crucible containing the mixed powder in step (2) to a high temperature T1 and keeping the temperature for a period of time t1 until the mixed powder in the crucible becomes a uniform melt;

[0017] (4) pouring the uniform melt in step (3) onto a mold to obtain a quenched precursor glass I;

[0018] (5) annealing the precursor glass I obtained in step (4) to obtain precursor glass II;

[0019] (6) Transfer the precursor glass II to a muffle furnace at a temperature of T2 and keep it warm for a period of time t2 to obtain a chemical formula of Na 5 Lu 9 F 32 :Eu glass-ceramic scintillator.

[0020] Furthermore, the reducing agent in step (2) includes one or more of Al powder and reducing carbon powder.

[0021] Furthermore, the adding amount of the reducing agent is 0-10 mol%.

[0022] Furthermore, the temperature T1 is 1300-1500°C, and the temperature T2 is 450-700°C.

[0023] Furthermore, time t1 is 1-2 hours, and time t2 is 1-4 hours.

[0024] Furthermore, in step (4), the temperature of the grinding tool is 300°C.

[0025] Furthermore, in step (5), the annealing temperature of the precursor glass I is 250-400° C., and the annealing time is 5-48 hours.

[0026] The present invention also provides an application of a microcrystalline glass scintillator, which is applied in X-ray imaging and luminescence detection.

[0027] In combination with the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solutions to be protected by the present invention are as follows:

[0028] First, in terms of cost and cycle, the scintillator preparation method provided by the present invention is simple and has a short cycle. The raw materials used are low in cost and have high economic value. The raw materials and finished products do not contain environmentally unfriendly elements such as lead, and there are no special requirements for recycling and treatment, which is convenient for promotion and use. More importantly, the present invention uses heat treatment in glass to induce crystallization in the glass. With the help of mature glass process technology, the present invention is suitable for industrial production.

[0029] Second, in terms of stability, the Na 5 Lu 9 F 32 :Eu glass-ceramic scintillator, Na 5 Lu 9 F 32 Eu crystal is the luminescent source of the scintillator. Its preparation method is to precipitate Na 5 Lu 9 F 32 :Eu crystal. On the one hand, the selected glass matrix has the characteristics of resistance to water, oxygen, high-energy radiation, heat, etc. 5 Lu 9 F 32 :Eu crystal has a good protective effect and can improve its stability. On the other hand, Na 5 Lu 9 F 32 :Eu crystal itself has extremely high thermal stability and high-energy radiation stability, which is the main factor determining whether it can be used in practice.

[0030] Third, the luminescent center of the scintillator of the present invention is Eu 2+ On the one hand, Eu 2+ It has a very high luminous efficiency and can fully match commercial Si and semiconductor detectors. 5 Lu 9 F 32 The crystal contains Lu elements, which can achieve the doping and concentration control of Eu ions, which solves the problem of difficulty in doping the luminescent center of the crystal scintillator and the inability to control the doping concentration.

[0031] Fourthly, the present invention provides a composition ratio of a glass matrix of a glass-ceramic scintillator, which can optimize the scintillation performance and provide a technical control method for industrial production and application.

[0032] The luminescent center of the scintillator in the present invention is Eu 2+ , substitution of ions of the same family can achieve the regulation of Eu ion concentration.

[0033] The present invention provides a method for realizing Eu 2+ The existing method specifically adopts the addition of reducing agents such as Al powder and reducing carbon powder; the present invention also provides a strategy for regulating the amount of reducing agent added, which helps to optimize the scintillator performance, such as scintillation fluorescence, light yield, etc.

[0034] The present invention also provides the melting temperature and crystallization temperature of the microcrystalline glass scintillator, which can optimize and regulate the performance of the scintillator. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 1 is a transmittance curve diagram of the scintillator of Example 1 and Example 2 of the present invention.

[0036] Figure 2 1 is a photoluminescence curve diagram of the scintillators of Examples 1 and 2 of the present invention.

[0037] Figure 3 These are X-ray excited luminescence images of the scintillators of Examples 1 and 2 of the present invention.

[0038] Figure 4 This is a TEM image of the scintillator of Example 2 of the present invention.

[0039] Figure 5 2 and 3 are XRD diagrams of the scintillators of Examples 2 and 3 of the present invention.

[0040] Figure 6 It is a fluorescence lifetime curve diagram of the scintillators of Examples 2 and 3 of the present invention.

[0041] Figure 7 This is a graph showing the X-ray attenuation coefficient of the scintillator of Example 2 of the present invention.

[0042] Figure 8 These are X-ray excited luminescence images of the scintillators of Examples 2 and 3 of the present invention.

[0043] Fig. 9 This is the X-ray scintillation luminescence diagram of Example 2 at different X-ray dose rates.

[0044] Fig.10 These are the transmittance spectra of Example 2 before irradiation and after irradiation at different radiation dose rates.

[0045] Fig.11 This is a graph showing the change in X-ray luminescence intensity of Example 2 under continuous X-ray irradiation.

[0046] Fig.12 This is a diagram showing an application example of the scintillator in Example 2. DETAILED DESCRIPTION

[0047] The following are examples of the present invention. It should be noted that the examples are more detailed descriptions of certain aspects, characteristics and embodiments of the present invention, and are not intended to limit the scope of the present invention. The present invention is not limited to the following examples. The methods described are conventional methods unless otherwise specified.

[0048] A Na 5 Lu 9 F 32 :Eu microcrystalline glass scintillator, the microcrystalline glass scintillator uses silicate glass as a matrix and Na5Lu9F32:Eu nanocrystals as luminescent centers.

[0049] The molar ratios of the glass components are: SiO 2 :36-56mol%Na 2 CO 3 :6-16mol%Al 2 O 3 : 9-21 mol%CaCO 3 :3-8mol%, NaF: 3-10mol%, LuF 3 : 4-15mol%,EuF 3 : 0-3 mol%.

[0050] The chemical formula of Na precipitated in the glass matrix is 5 Lu 9 F 32 :Crystalline of Eu.

[0051] The Na 5 Lu 9 F 32 A method for preparing a Eu glass-ceramic scintillator comprises the following steps:

[0052] S1: Accurately weigh SiO 2 , Na 2 CO 3 , Al 2 O 3 , CaCO 3 , NaF, LuF 3 , GdF 3 etc., and mix thoroughly;

[0053] S2: weighing a reducing agent, and adding the reducing agent to the mixture in step S1, and transferring the mixture into an alumina crucible after fully mixing;

[0054] S3: transferring the crucible containing the mixed powder in step S2 to a high temperature T1 and keeping the temperature for a period of time t1 until the mixed powder in the crucible becomes a uniform melt;

[0055] S4: pouring the uniform melt in step S3 onto a mold at a temperature of 300° C. to obtain a quenched precursor glass I;

[0056] S5: annealing the precursor glass obtained in step S4 to obtain precursor glass II;

[0057] S6 transfers the precursor glass II to a muffle furnace at a temperature of T2 and keeps it warm for a period of time t2 to obtain a chemical formula of Na 5 Lu 9 F 32 :Eu glass-ceramic scintillator.

[0058] The reducing agent in step S2 includes but is not limited to Al powder, reducing carbon powder, etc.

[0059] The amount of reducing agent added in step S2 is 0-10 mol%.

[0060] In steps S3 and S6, temperature T1 is 1300-1500° C., temperature T2 is 450-700° C.; time t1 is 1-2 hours, and time t2 is 1-4 hours.

[0061] The annealing temperature of the precursor glass I is 250-400° C., and the annealing time is 5-48 hours.

[0062] In the present invention, Eu 3+ Reduced to Eu 2+ ,Eu 2+ Become a luminous center.

[0063] In order to make the disclosure of the present invention more complete, it is described below through more specific embodiments.

[0064] Embodiment 1:

[0065] A Na 5 Lu 9 F 32 A method for preparing a Eu glass-ceramic scintillator comprises the following steps:

[0066] (1) According to SiO 2 : 45 mol%Na 2 CO 3 : 10 mol%Al 2 O 3 : 15 mol%CaCO 3 : 4mol%, NaF: 6mol%, LuF 3 : 8mol%,EuF 3 : 2 mol% accurately weighed raw materials;

[0067] (2) After thorough mixing, transfer into an alumina crucible;

[0068] (3) preparing the precursor glass by melt quenching method in step (2), with the melting temperature at 1400° C. and keeping the temperature for 1 hour;

[0069] (4) heat treating the precursor glass obtained in step (3) at 620° C. for 2 hours;

[0070] (5) Performing crystallization treatment at a crystallization temperature of 620° C. for 1 hour, obtaining a product having a chemical formula of Na 5 Lu 9 F 32 :Eu glass-ceramic scintillator.

[0071] Embodiment 2:

[0072] A Na 5 Lu 9 F 32 A method for preparing a Eu glass-ceramic scintillator comprises the following steps:

[0073] (1) According to SiO 2 : 45 mol%Na 2 CO 3 : 10 mol%Al 2 O 3 : 15 mol%CaCO 3 : 4mol%, NaF: 6mol%, LuF 3 : 8mol%,EuF 3 : 2 mol% accurately weighed raw materials;

[0074] (2) adding an additional 2.7 mol% of Al as a reducing agent, mixing thoroughly and transferring into an alumina crucible;

[0075] (3) preparing the precursor glass by melt quenching method in step (2), with the melting temperature at 1400° C. and keeping the temperature for 1 hour;

[0076] (4) heat treating the precursor glass obtained in step (3) at 620° C. for 2 hours;

[0077] (5) Performing crystallization treatment at a crystallization temperature of 620° C. for 1 hour, obtaining a product having a chemical formula of Na 5 Lu 9 F 32 :Eu glass-ceramic scintillator.

[0078] Embodiment 3:

[0079] A Na 5 Lu 9 F 32 A method for preparing a Eu glass-ceramic scintillator comprises the following steps:

[0080] (1) According to SiO 2 : 45 mol%Na 2 CO 3 : 10 mol%Al 2 O 3 : 15 mol%CaCO 3 : 4mol%, NaF: 6mol%, LuF 3 : 8mol%,EuF 3 : 2 mol% accurately weighed raw materials;

[0081] (2) adding an additional 2.7 mol% of Al as a reducing agent, mixing thoroughly and transferring into an alumina crucible;

[0082] (3) preparing the precursor glass by melt quenching method in step (2), with the melting temperature at 1400° C. and keeping the temperature for 1 hour;

[0083] (4) heat treating the precursor glass obtained in step (3) at 620° C. for 2 hours;

[0084] (5) Performing crystallization treatment at a crystallization temperature of 630° C. for 1 hour, obtaining a product having a chemical formula of Na 5 Lu 9 F 32 :Eu glass-ceramic scintillator.

[0085] Figure 1 The scintillator transmittance spectra obtained in Example 1 and Example 2 show that the scintillators in both examples have relatively high transmittance (>80%). 3+ Restored to Eu 2 + The transmittance spectrum of the scintillator in Example 1 has shifted significantly. The transmittance of the scintillator in Example 1 observed absorption peaks at 394nm and 464nm, corresponding to Eu 3+ of 7 F 0 → 5 L 7 , 5 D 2 Transition. In the transmittance curve of the scintillator in Example 2, the above absorption transition weakens or even disappears. In addition, the absorption also red-shifts from 274nm to 384nm. This also shows that Eu 3+ Restored to Eu 2+ .

[0086] Figure 2 The scintillator spectra obtained in Example 1 and Example 2 are both 374 nm in excitation wavelength. The luminescence of the scintillator in Example 1 is a typical Eu 3+ The luminescence spectrum of the scintillator in Example 2 has a luminescence peak at 620 nm. The luminescence peak of the scintillator in Example 2 is at 475 nm, and the typical Eu 2+ Glow.

[0087] Figure 3The luminescence spectra of the scintillators obtained in Example 1 and Example 2 are X-ray excited luminescence spectra. The luminescence peak of the scintillator in Example 1 is mainly located near 620nm, and the luminescence of the scintillator in Example 2 is mainly located near 475nm, and the luminescence integral intensity of Example 2 is much greater than that of Example 1. Taking a commercial BGO crystal of the same thickness as a comparative example, under X-ray irradiation (tube voltage 50kV, tube current 200 microamperes), the luminescence integral intensity of Example 2 is greater than that of BGO. In comparison, the luminescence integral intensity of Example 1 is much less than that of BGO.

[0088] Figure 4 This is the TEM image of the scintillator of Example 2. As shown in the figure, crystals are uniformly precipitated in the glass, the crystal size is about 12nm, and the distance between the crystals is good. The precipitated crystal scintillators are protected by the glass matrix and avoid agglomeration between nanoparticles.

[0089] Figure 5 3 are the XRD diagrams of Example 2 and Example 3. As shown in the figure, after heat treatment, the microcrystalline glass scintillator has a very good crystal phase, and the X-ray diffraction peak matches well with the standard card.

[0090] Figure 6 The Na obtained in Example 2 and Example 3 5 Lu 9 F 32 The results show that the fluorescence lifetime of Eu glass-ceramic scintillator is 1.50 μs and 1.53 μs, which is much lower than that of rare earth ions (Tb 3+ 、Eu 3+ )The lifetime of the doped glass scintillator is very short (milliseconds), which is beneficial for X-ray imaging.

[0091] Figure 7 : is the X-ray attenuation coefficient curve of the scintillator of Example 2. As shown in the figure, the scintillator of Example 2 shows a strong X-ray absorption efficiency, and its absorption efficiency at 61-89 KeV is better than that of BGO, which shows that it is suitable for medical digital radiography.

[0092] Figure 8 The scintillator of Example 2 and Example 3 are X-ray excited luminescence spectra, and their scintillation luminescence efficiency exceeds that of BGO, reaching 121% of BGO, which indicates that the scintillator of the present invention has a wide range of application prospects.

[0093] Fig. 9 The X-ray scintillation luminescence of Example 2 at different X-ray dose rates shows that the luminescence intensity of the scintillator is significantly enhanced with the increase of dose. Fig.10The transmittance spectra before and after irradiation at different radiation dose rates show that even after irradiation with a high dose of 81.78 mGy / s of X-rays, the transparency of the scintillator in Example 2 is almost not reduced. This proves that the scintillator in the present invention can be used in a high dose rate radiation environment.

[0094] Fig.11 The X-ray luminescence intensity change of Example 2 under continuous X-ray irradiation, that is, the working stability of the scintillator. As shown in the figure, after 150 minutes of irradiation, the total dose reaches 414.27Gy, which is equivalent to 2 million X-ray chest radiographs in the hospital (0.2mGy each time). The scintillation luminescence intensity of the scintillator in the present invention does not decrease, but shows a trend of increasing and then stabilizing, which shows that the scintillator in the present invention has excellent radiation resistance.

[0095] Fig.12 The X-ray imaging performance of the scintillator in Example 2 shows that the internal structure of the chip, the metal spring in the capsule and the iron nail with a spiral structure can be clearly seen. More importantly, the imaging resolution of the scintillator in the present invention is as high as 20lp / mm, which is suitable for high-resolution X-ray imaging.

Claims

1. A method for preparing a glass-ceramic scintillator, characterized in that: The microcrystalline glass scintillator is based on silicate glass and Na5Lu9F 32 :Eu nanocrystals are the luminescence centers; The molar ratios of the glass components of the microcrystalline glass scintillator are: SiO2: 36-56mol%, Na2CO3: 6-16mol%, Al2O3: 9-21mol%, CaCO3: 3-8mol%, NaF: 3-10mol%, LuF3: 4-15mol%, EuF3: 0-3mol%; The method for preparing the microcrystalline glass scintillator comprises the following steps: (1) Accurately weigh SiO2, Na2CO3, Al2O3, CaCO3, NaF, LuF3, and EuF3 raw materials and mix them thoroughly; (2) weighing a reducing agent and adding the reducing agent to the mixture in step (1), mixing thoroughly and transferring the mixture into an alumina crucible; (3) heating the crucible containing the mixed powder in step (2) to a high temperature T1, and maintaining the temperature for a period of time t1 until the mixed powder in the crucible becomes a uniform melt; (4) pouring the uniform melt in step (3) onto a mold to obtain a quenched precursor glass I; (5) annealing the precursor glass I obtained in step (4) to obtain precursor glass II; (6) Transfer the precursor glass II to a muffle furnace at a temperature of T2 and keep it warm for a period of time t2 to obtain a chemical formula of Na5Lu9F 32 :Eu glass-ceramic scintillator; The temperature T1 is 1300-1500°C, and the temperature T2 is 450-700°C.

2. The method for preparing a glass-ceramic scintillator according to claim 1, characterized in that: The reducing agent in step (2) includes one or more of Al powder and reducing carbon powder.

3. The method for preparing a glass-ceramic scintillator according to claim 2, characterized in that: The adding amount of the reducing agent is 0-10 mol%.

4. The method for preparing a glass-ceramic scintillator according to claim 1, characterized in that: The time t1 is 1-2 hours, and the time t2 is 1-4 hours.

5. The method for preparing a glass-ceramic scintillator according to claim 1, characterized in that: The temperature of the mold in step (4) is 300°C.

6. The method for preparing a glass-ceramic scintillator according to claim 1, characterized in that: In step (5), the annealing temperature of the precursor glass I is 250-400° C., and the annealing time is 5-48 hours.

7. An application of a glass-ceramic scintillator prepared by the method according to any one of claims 1 to 6, characterized in that: Used in the field of X-ray detection.

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