A cerium ion doped high-entropy fluoride scintillation crystal, a preparation method and application thereof

Abstract

This invention relates to a cerium ion-doped high-entropy fluoride scintillation crystal, its preparation method, and its applications. The preparation method involves using single crystal particles or powders of LaF3, GdF3, CaF2, SrF2, BaF2, and CeF3 as raw materials, doping them with Ce ions, grinding them uniformly to obtain a matrix material, vacuuming, and then performing high-temperature sintering to ensure complete matrix material solidification and impurity removal. The material is then slowly cooled to allow crystal growth, reaching room temperature to obtain the cerium ion-doped high-entropy fluoride scintillation crystal. The chemical formula of the high-entropy fluoride scintillation crystal is Ce:M1M2CaSrBaF2. 12 Where M1 and M2 are any two of Y, Lu, Gd, La, Lu, Sc, and Ce. Compared with the prior art, the LaGdCaSrBaF prepared by this invention... 12 High-entropy crystals possess lower phonon energies and smaller 5d level splitting, which can significantly reduce Ce. 3+ The probability of nonradiative transitions to the 5d energy level of ions decreases. Furthermore, the disordered distribution of mixed crystals allows for the modulation of Ce at the atomic, molecular, and group scales. 3+ The local coordination structure of ions allows them to achieve true disorder.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of crystal materials, in particular to a cerium ion doped high-entropy fluoride scintillation crystal and a preparation method and application thereof. BACKGROUND

[0002] A scintillator is a material that can convert high-energy radiation into visible light, and is widely used in high-energy physics detection, nuclear medical imaging, security equipment and other fields. The core principle is that when high-energy particles (such as X-rays or gamma rays) irradiate the scintillator material, the inner layer electrons of the scintillator are excited to become free electrons, and the inner layer electrons further undergo scattering and excitation Auger electrons, and through thermal effects, free electrons and free holes are gathered at the top of the material valence band and the bottom of the conduction band. Finally, when the free electrons and holes return to the ground state, energy is released in the form of photons. The light produced in this process is called scintillation light, and the performance of the scintillator determines the intensity, stability and response speed of the light output. In 1903, William Crookes first published the use of ZnS scintillators to count alpha particles. By the end of the twentieth century, E.D. Bourret-Courchesne and S.E. Derenzo and others conducted in-depth research on the performance and growth process of cerium-doped materials such as alkaline earth halides, and these studies showed that by optimizing the doping concentration and improving the crystal growth technology, the optical performance of these scintillators can be significantly improved.

[0003] Cerium ions (Ce3+) as a commonly used scintillation center, due to its 4f→5d transition has a faster light response time and higher photon yield, are widely used in scintillators. Especially in oxide and fluoride matrix materials, the doping of cerium ions can significantly improve the photoluminescence performance of the scintillator, while maintaining the high mechanical strength and chemical stability of the material. In addition, cerium-doped scintillator materials usually have a short scintillation decay time, which is crucial for detection applications that require high time resolution. The 5d energy level of cerium ions is greatly affected by the crystal field, and the weak field environment of fluoride makes the 5d energy level splitting not serious, and the non-radiative transition probability in the 5d energy level is small. In 2007, G. Bizarri and P. Dorenbos explained in detail the energy transfer process from self-trapped excitons to cerium ions in cerium-doped lanthanum bromide crystal materials and the influence on the entire scintillation decay process. So far, the growth method of cerium-doped alkaline earth halide crystals, the type of materials and the characterization means have undergone long-term development and have made great achievements. However, it is still unknown how the scintillation performance of the scintillator in the strong lattice distortion environment caused by high entropy.

[0004] High-entropy materials are a new class of multi-component alloys or compounds that have emerged in recent years. They are typically composed of five or more elements in near-equiatomic proportions. Compared to traditional single or binary component materials, high-entropy materials exhibit more complex and unique characteristics in chemical composition, atomic arrangement, and physical properties. These materials often show excellent mechanical properties, thermal stability, and corrosion resistance, thus attracting wide attention in the field of structural materials.

[0005] As research deepens, the concept of high-entropy materials has gradually expanded from metal alloys to functional materials such as ceramics, oxides, and fluorides. In the field of scintillators, the introduction of high-entropy materials has multiple potential advantages. First, the lattice distortion caused by high-entropy effect helps to improve the energy resolution and light yield of scintillator materials, as the mixing of different atomic sizes can enhance the localization effect of excited states, thus improving the luminescence efficiency. Second, the element diversity in high-entropy materials provides rich doping options, which can optimize the luminescence spectrum and response speed of scintillators. For example, by introducing different rare earth elements into a fluoride matrix, it is possible to achieve luminescence control in a wide band or specific wavelength range to meet different application requirements.

[0006] In cerium ion-doped LaGdCaSrBaF 12 In high-entropy base scintillators, the material is composed of five or more alkaline earth metals and rare earth metals, forming a highly complex crystal structure. The uniqueness of high-entropy materials lies in the presence of multiple elements with different valence states, which form complex interactions with each other. This structure not only endows the material with stronger radiation resistance and chemical stability, but also effectively suppresses the defect states in the crystal, reduces non-radiative transition processes, and improves the photoluminescence efficiency.

[0007] Cerium-doped LaGdCaSrBaF 12 High-entropy base scintillators exhibit excellent photoluminescence performance, indicating that the material can produce intense visible light after excitation. This suggests that under the influence of high-entropy base, excited carriers effectively participate in photon emission. At the same time, the photoluminescence decay time of this material reaches an extremely excellent 5.74 ns (82.9%). However, although the photoluminescence performance is good, the characteristics of scintillation decay time have not been tested. Decay time is an important parameter for evaluating the response speed of scintillators, usually related to the excited state lifetime of the doped ions in the material. The complex lattice environment of high-entropy materials may have an impact on the decay time, which is worth further testing and analysis in future research. SUMMARY

[0008] The purpose of the present invention is to overcome the defects of the prior art and provide a cerium ion-doped high-entropy fluoride scintillation crystal, its preparation method and application. The prepared Ce:LaGdCaSrBaF 12The high lattice distortion environment provided by the high-entropy matrix in the high-entropy crystal provides more energy traps for the formation of self-trapped excitons, so that the energy transfer efficiency of the self-trapped excitons to the luminescent center is higher, and the scintillation performance of the material is better. The hysteresis diffusion effect caused by high entropy improves the radiation hardness of the material and can enhance the service life of the material.

[0009] The object of the present application can be achieved by the following technical solutions:

[0010] The present application provides a cerium ion doped high-entropy fluoride scintillation crystal, the chemical formula of the scintillation crystal is Ce:M1M2CaSrBaF 12 , wherein M1 and M2 are any two of Y, Lu, Gd, La, Lu, Sc, and Ce.

[0011] The space group of the scintillation crystal is Fm-3m (225), which belongs to the cubic system.

[0012] Further, the chemical formula of the scintillation crystal is Ce:LaGdCaSrBaF 12 .

[0013] The present application also provides a preparation method of a cerium ion doped high-entropy fluoride scintillation crystal, comprising the following steps:

[0014] S1: taking single crystal particles or powders of LaF3, GdF3, CaF2, SrF2, BaF2 and CeF3 as raw materials and doping Ce ions, and grinding uniformly to obtain a matrix material;

[0015] S2: loading the matrix material in S1 into a porous graphite crucible, covering a lid to prevent the evaporation of a large amount of raw materials, and placing in a hot field to extract vacuum;

[0016] S3: after good vacuum extraction, starting the power to heat and keep warm for a period of time to ensure that the matrix material in S1 is completely melted and impurities are removed, then slowly cooling down, and after the growth is completed, cooling down to room temperature to obtain a cerium doped high-entropy fluoride scintillation crystal.

[0017] Further, in S1, the purity of the single crystal particles or powders of LaF3, GdF3, CaF2, SrF2, BaF2 and CeF3 is 5N.

[0018] Further, in S1, the grinding time is 40-60 min.

[0019] In S1, the doping molar mass ratio of the Ce ions is 0.5%-3.0%.

[0020] Further, in S1, 1wt.% of PbF2 is added to the matrix material, and the PbF2 is used as an oxygen scavenger to prevent the oxidation of the fluoride raw materials.

[0021] Furthermore, in S2, the vacuum is evacuated to below 8 Pa.

[0022] Furthermore, in S3, the heating rate is 100-200℃ / h, the temperature is raised to 1350-1400℃, and the holding time is 8-12h.

[0023] Furthermore, in S3, the cooling rate of the slow cooling is 1.5℃ / h;

[0024] In S3, the growth ends by slowly cooling to 150°C, and then cooling down to room temperature at a rate of 30-50°C / h.

[0025] The present invention also provides an application of cerium ion-doped high-entropy fluoride scintillation crystal, which is used in the preparation of radiation detection materials.

[0026] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0027] 1. This invention uses LaGdCaSrBaF 12 High-entropy crystals are used as matrix materials for scintillation crystals, with Ce 3+ Ion doping of LaGdCaSrBaF 12 Due to the difficulty in growing high-entropy fluoride materials within the crystal lattice, this invention has successfully grown a high-entropy fluoride bulk single crystal that has not been reported to date.

[0028] 2. Ce:LaGdCaSrBaF prepared in this invention 12 The high-entropy matrix in high-entropy crystals provides a high-lattice distortion environment, offering more energy traps for the formation of self-trapped excitons. This results in higher energy transfer efficiency from self-trapped excitons to the luminescent center, leading to better scintillation performance. The hysteresis diffusion effect induced by high entropy increases the radiation hardness of the material, thereby enhancing its service life.

[0029] 3. Ce:LaGdCaSrBaF prepared by this invention 12 High-entropy crystals possess lower phonon energies and smaller 5d level splitting, which can significantly reduce Ce. 3+ The probability of nonradiative transitions to the 5d energy level of ions decreases. Furthermore, the disordered distribution of mixed crystals allows for the modulation of Ce at the atomic, molecular, and group scales. 3+ The localized coordination structure of the ions allows them to achieve true disorder. Furthermore, high-entropy fluoride scintillation crystals can achieve shorter scintillation times and stronger radiation resistance. Attached Figure Description

[0030] Figure 1 The fluorescence spectrum of the sample prepared in Example 1 excited under 280 nm light at room temperature;

[0031] Figure 2 The fluorescence lifetime spectrum of the sample prepared in Example 1 under 280 nm light excitation corresponding to the 320 nm emission peak. DETAILED DESCRIPTION

[0032] The specific embodiments of the present application are described in detail below with examples, which are implemented on the premise of the scheme described in the present application, and detailed implementation and specific operation process are given, but the protection scope of the present application is not limited to the examples below.

[0033] The present application is further described below in combination with the drawings and specific examples. In the technical scheme, if the component model, material name, connection structure, preparation means, material, structure or component ratio and other features are not explicitly stated, they are regarded as common technical features disclosed in the prior art.

[0034] Example 1

[0035] The present embodiment provides a LaGdCaSrBaF 12 The preparation method of the crystal is as follows:

[0036] Put 24.8232 g of LaF3, 27.1484 g of GdF3, 9.8925 g of CaF2, 15.9177 g of SrF2, 22.218 g of BaF2 and 1.0 g of PbF2 raw materials into a graphite crucible, grind them uniformly, cover the lid, put them into the furnace to extract vacuum, extract vacuum to below 8 Pa, then heat to 1350 ℃ at a heating rate of 300 ℃ / h, keep the temperature constant for 8 hours until the raw materials are completely melted and the impurities are completely removed, then slowly cool at a rate of 1.5 ℃ / h for growth. After cooling to 150 ℃, i.e. the end of growth, cool to room temperature at a rate of 30 ℃ / h, then take out the crystal, and obtain a LaGdCaSrBaF 12 crystal, which is recorded as pure LGCSB.

[0037] Figure 1 The fluorescence spectra of the five high-entropy fluoride single crystal samples prepared in Examples 1-5 under 280 nm excitation at room temperature. As can be seen from the figure, there is energy transfer from gadolinium ions to cerium ions, and the cerium ion luminescence peak red shifts with the increase of cerium ion concentration.

[0038] Figure 2 The fluorescence lifetime spectrum of the four high-entropy fluoride single crystal samples doped with cerium ions under 250 nm light excitation corresponding to the 320 nm emission peak, it can be seen that the photoluminescence decay time in the cerium doped sample reaches an extremely fast 5.74 ns, and the fast component accounts for 82.9%.

[0039] Table 1 is the fluorescence decay time of four high-entropy fluoride single crystal samples prepared in Examples 2-5 at room temperature, from which it can be seen that the fluorescence decay time of the high-entropy scintillator material is several times shorter than that of the general cerium-doped scintillator material, laying a foundation for the high-entropy scintillator material.

[0040] Table 1 Fluorescence lifetime fitting statistics table corresponding to 320 nm emission peak under 250 nm light excitation

[0041]

[0042] Example 2

[0043] This example provides a 0.5% Ce: LaGdCaSrBaF 12 The preparation method of the crystal is as follows:

[0044] To the initial raw material with a purity of 5N, 24.6685g of LaF3, 26.979g of GdF3, 9.8308g of CaF2, 15.8185g of SrF2, 22.0794g of BaF2, 0.6236g of CeF3, and 1.0g of PbF2, 0.5% Ce ions are added to replace the cations in a molar mass ratio, ground and mixed uniformly. The weighed raw material is placed in a porous graphite crucible and covered with a circular graphite cover with a diameter of 1mm, and then the furnace is vacuumized and high-purity argon is filled as a protective atmosphere. The temperature is raised to 2140℃ at a rate of 320℃ / h, and the temperature is kept constant for 3 hours until the raw material is completely melted. Slowly cool down at a rate of 1.5℃ / h for growth. After cooling to 150℃, i.e. the end of growth, cool down to room temperature at a rate of 50℃ / h, and then take out the crystal. A 0.5% Ce: LaGdCaSrBaF 12 crystal is obtained.

[0045] The prepared 0.5% Ce: LaGdCaSrBaF 12 crystal has a transmittance greater than 80%, a fluorescence lifetime of 5.74ns, and a fast component ratio of 82.9%.

[0046] Example 3

[0047] This example provides a 1.0% Ce: LaGdCaSrBaF 12A method for preparing the crystal, which is different from that of Example 2 in that, in the present example, 1.0% of Ce ions are added to replace cations in the starting material 24.5141 g of LaF3, 26.8102 g of GdF3, 9.7693 g of CaF2, 15.7194 g of SrF2, 21.9412 g of BaF2, 1.2457 g of CeF3, and 1.0 g of PbF2 raw single crystal particles with a purity of 5N, and the remaining steps are the same as those of Example 2, to obtain 1.0% Ce:LaGdCaSrBaF 12 crystal.

[0048] The prepared 1.0% Ce:LaGdCaSrBaF 12 The crystal has a transmittance of greater than 80%, a fluorescence lifetime of 5.90 ns, and a fast component ratio of 81.9%.

[0049] Example 4

[0050] The present example provides a 3.0% Ce:LaGdCaSrBaF 12 A method for preparing the crystal, which is different from that of Example 2 in that, in the present example, 3.0% of Ce ions are added to replace cations in the starting material 23.9181 g of LaF3, 26.1584 g of GdF3, 9.5318 g of CaF2, 15.3373 g of SrF2, 21.4078 g of BaF2, 3.6463 g of CeF3, and 1.0 g of PbF2 raw single crystal particles with a purity of 5N, and the remaining steps are the same as those of Example 2, to obtain 3.0% Ce:LaGdCaSrBaF 12 crystal.

[0051] The prepared 3.0% Ce:LaGdCaSrBaF 12 The crystal has a transmittance of greater than 80%, a fluorescence lifetime of 6.23 ns, and a fast component ratio of 81.7%.

[0052] Example 5

[0053] The present example provides a LaCeCaSrBaF 12 A method for preparing the crystal, the specific process being:

[0054] LaF3, 25.531 g of CeF3, 10.1121 g of CaF2, 16.2711 g of SrF2, 22.7112 g of BaF2 and 1.0 g of PbF3 were put into a graphite crucible, the furnace was vacuumized to below 8 Pa, heated to 1340 °C at a heating rate of 340 °C / h, kept at 1340 °C for 8 hours until the raw materials were completely melted and impurities were completely removed, then slowly cooled at a rate of 1.5 °C / h to grow the crystal. After the temperature was decreased to 150 °C, i.e. the end of the growth, the temperature was decreased to room temperature at a rate of 35 °C / h, and a LaCeCaSrBaF4 crystal with good optical quality was obtained. 12 The crystal is denoted as pure LCCSB.

[0055] The above description of the embodiments is to enable those skilled in the art to understand and use the invention. Those skilled in the art can easily make various modifications to the embodiments and apply the general principles described herein to other embodiments without creative effort, which should be within the scope of the invention. Therefore, the invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the invention without departing from the scope of the invention should be within the protection scope of the invention.

Claims

1. A cerium ion doped high-entropy fluoride scintillation crystal, characterized in that, The chemical formula of the scintillation crystal is Ce:LaGdCaSrBaF 12 ; The space group of the scintillation crystal is Fm-3m (225), belonging to the cubic system.

2. A method of preparing a cerium ion doped high-entropy fluoride scintillation crystal as claimed in claim 1, characterized in that, The method comprises the following steps: S1: taking single crystal particles or powder of LaF3, GdF3, CaF2, SrF2, BaF2 and CeF3 as raw materials, doping Ce ions, and grinding uniformly to obtain a matrix material; S2: loading the matrix material in S1 into a porous graphite crucible, covering a lid to prevent massive volatilization of the raw materials, and placing in a hot field for vacuum pumping; S3: after vacuum pumping, starting power to heat and keep warm for a period of time to ensure that the matrix material in S1 is completely melted and impurities are removed, then slowly cooling, growing crystals, and after the growth is completed, cooling to room temperature to obtain a cerium-doped high-entropy fluoride scintillation crystal.

3. The method of claim 2, wherein the Ce-ion doped high-entropy fluoride scintillation crystal is prepared by the following steps: In S1, the purity of the single crystal particles or powder of LaF3, GdF3, CaF2, SrF2, BaF2 and CeF3 is 5N. ​ 4. The method of claim 2, wherein the Ce-ion doped high-entropy fluoride scintillation crystal is prepared by the following steps: In S1, the grinding time is 40-60 min; ​ In S1, the doping molar mass ratio of the Ce ions is 0.5%-3.0%.

5. The method of claim 2, wherein the Ce-ion doped high-entropy fluoride scintillation crystal is prepared by the method comprising: providing a fluoride crystal; and doping the fluoride crystal with Ce ions. In S1, 1wt.% of PbF2 is added to the matrix material, and the PbF2 is used as an oxygen scavenger to prevent oxidation of the fluoride raw materials.

6. The method of claim 2, wherein the Ce-ion doped high-entropy fluoride scintillation crystal is prepared by the method comprising: providing a fluoride crystal; and doping the fluoride crystal with Ce ions. In S2, the vacuum pumping is pumped to below 8 Pa.

7. The method of claim 2, wherein the Ce-ion doped high-entropy fluoride scintillation crystal is prepared by the method comprising: providing a fluoride crystal; and doping the fluoride crystal with Ce ions. In S3, the heating rate is 100-200℃ / h, the temperature is raised to 1350-1400℃, and the constant temperature time is 8-12 h.

8. The method of claim 2, wherein the Ce-ion doped high-entropy fluoride scintillation crystal is prepared by the method comprising: providing a fluoride crystal; and doping the fluoride crystal with Ce ions. In S3, the slow cooling rate is 1.5℃ / h. In S3, the end of the growth is slow cooling to 150℃, and then cooling to room temperature at a cooling rate of 30-50℃ / h.

9. Use of a cerium ion doped high-entropy fluoride scintillation crystal as claimed in claim 1, characterized in that, The cerium ion-doped high-entropy fluoride scintillation crystal is used in the preparation of radiation illuminating materials.

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