Rare earth silicon germanate scintillating material as well as preparation method and application thereof

Abstract

The invention provides a rare earth silicon germanate scintillating material and a preparation method and application thereof, in particular to a rare earth silicon germanate scintillating material with high thermal stability and strong radiation resistance and a preparation method and application thereof, the general formula of the rare earth silicon germanate scintillating material with high thermal stability and strong radiation resistance is RE2 (1-x-delta / 2) Ce2xGedeltaSi (1-y + delta) Gey-deltaOz, in the formula, 0 lt; x is more than or equal to 0.05, y is more than or equal to 0.15 and less than or equal to 0.5, delta is more than or equal to 0 and less than or equal to 10 <-4 >, z is more than or equal to 4.95 and less than or equal to 5.05, RE represents a rare earth element, and the rare earth element is selected from at least one of lanthanum (La), lutetium (Lu), yttrium (Y) and gadolinium (Gd). The rare earth silicon germanate scintillating material provided by the invention has the characteristics of strong radiation damage resistance, high scintillation light output, low afterglow and the like while greatly improving the thermal stability, and can be used in occasions with extremely high requirements on the thermal stability or radiation resistance of the material, such as high-energy physical experiments, nuclear medicine imaging, oil exploration wells and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of scintillation materials, and in particular to a rare earth germanosilicate scintillation material, a preparation method and applications thereof, and more particularly to a rare earth germanosilicate scintillation material with high thermal stability and strong radiation resistance, a preparation method and applications thereof. Background Art

[0002] Scintillator crystals emit visible light when interacting with high-energy ionizing radiation (such as X-rays or gamma rays) or high-energy particles (including electrons, protons, and neutrons). Scintillation detectors based on inorganic scintillator crystals have important applications in medical imaging, cutting-edge particle physics, and defense nuclear technology. Rare earth-doped silicate materials, due to their high light output, fast decay times, and excellent energy resolution, have become core materials in nuclear medicine imaging (X-CT or PET-CT) and high-energy physics detection.

[0003] However, in applications such as nuclear power plant accident monitoring, high energy physics and well logging, scintillators are often exposed to harsh conditions such as high temperature and / or high radiation levels. Under high-dose radiation, scintillators suffer radiation damage, are prone to color center defects, and radiation-induced additional absorption bands appear, resulting in a decrease in the inherent scintillation light output. Additional effects also include causing afterglow, which leads to an increase in readout noise. Oxide scintillators are usually grown in an oxygen-deficient inert atmosphere and are prone to oxygen vacancy defects. After irradiation with high-energy rays, a large number of color centers are generated, resulting in a decrease in scintillation performance. In addition, under high-temperature environments, the competition between radiative recombination and non-radiative recombination in the crystal is unbalanced. The enhancement of non-radiative paths (such as phonon coupling and defect activation) significantly reduces the light output efficiency. Therefore, scintillators not only need to have typical characteristics such as high light output, large stopping power, and short decay time, but also need to be able to maintain acceptable scintillation performance in high temperature and high radiation environments. Ce 3+ As a luminescence center, there is a temperature quenching effect. As the temperature increases from 300 K to 550 K, the decay time of LYSO:Ce scintillator decreases from 42 ns to 1.89 ns, and the light output decreases from 32000 ph. / MeV to 1120 ph. / MeV (AIP Advances, 2022, 12(6): 065003.). Although traditional rare earth orthosilicate scintillators (such as LSO:Ce and LYSO:Ce) are considered to be more radiation-resistant than other commonly used scintillators, radiation hardness studies have found that the light output of LYSO:Ce scintillator decreases by about 26.6% after irradiation with 3.83 MGy γ-rays, and can only recover to 89.4% of the original light output after thermal annealing at 300 °C for 24 hours (Radiation Physics and Chemistry, 2021, 183: 109396.).

[0004] In recent years, relevant literature has focused on improving scintillation performance through low-valent ion doping and heat treatment processes, but such methods often only optimize light output and decay time indicators, and fail to take into account the comprehensive requirements of thermal quenching resistance and radiation resistance. For example, patent US8278624B2 discloses a method of improving scintillation performance by Ca 2+ Mg 2+ and Zn 2+ Method for improving the scintillation performance of LSO crystals by co-doping with divalent cations, the improvement mechanism involves Ce 4+ Fast flash luminescence and regulation of electron traps. Although this method optimizes the light output and decay time characteristics, due to the charge balance rule, more positively charged oxygen vacancies and Ce with energy levels closer to the bottom of the conduction band are generated in the lattice. 4+ ions, which deteriorates the scintillator's resistance to radiation damage and significantly reduces its thermal quenching temperature (IEEE Transactions on Nuclear Science, 2013, 60(4): 3134-3141). Furthermore, patent CN119194617A discloses a method of treating rare earth orthosilicate scintillator crystals with corrosion, plasma injection, and annealing diffusion to reduce oxygen vacancy defect concentration, optimize energy resolution, and reduce afterglow. Although this treatment can improve radiation resistance or partially repair radiation damage, it has no effect on thermal stability and increases process complexity and cost. Currently, no technology can effectively solve the problems of high-temperature thermal quenching and radiation damage in rare earth silicate crystals. Summary of the Invention

[0005] In accordance with practical application needs and to solve the above-mentioned background technical problems, the purpose of the present invention is to provide a rare earth germanium silicate scintillating material with high thermal stability, strong resistance to radiation damage, high light output and low afterglow, as well as its preparation method and application.

[0006] According to the first aspect of the present invention, a rare earth germanium silicate scintillating material with high thermal stability and strong radiation resistance is provided, which is a new type of rare earth germanium silicate scintillating material with the general formula RE 2(1-x-δ / 2) Ce 2x Ge δ Si (1-y+δ) Ge y-δ O z , wherein RE is a rare earth ion selected from one or more combinations of lanthanum (La), lutetium (Lu), yttrium (Y), and gadolinium (Gd), wherein: <x≤0.05,0.15≤y≤0.5,0≤δ≤10 -4 , and 4.95≤z≤5.05.

[0007] This technical solution introduces high concentration of Ge into the rare earth orthosilicate system. 4+ions (≥15%), the significance of this design is that: the inventors of this application found that the previous Chinese patent application CN118639330A disclosed a co-doped rare earth orthosilicate scintillating material with improved performance, preparation method and application. The patent doped 0.3%~10% Ge in the silicon lattice. 4+ , can affect the activation center on the rare earth lattice through the oxygen ions and oxygen vacancies on [SiO4], thereby improving the scintillation performance. Based on this patent, the inventor of this application has found through a large number of experimental verifications that low concentrations of Ge 4+ Doping (≤10%) does not introduce fast-emitting Ce 4+ , lattice perturbation is limited, Ce 3+ The energy levels and oxygen vacancy traps are not effectively regulated, and the improvement of scintillation performance is limited. 4 + (≥15%) leads to significant lattice expansion, Ce 3+ The 5d state energy level is lowered (luminescence redshift), and by suppressing the formation of oxygen vacancies, the synergistic optimization of scintillation light output, afterglow, radiation resistance and thermal stability is achieved.

[0008] Specifically, first of all, because rare earth orthosilicate and rare earth germanate, such as Lu2SiO5 and Lu2GeO5, have the same space group, it can ensure high concentration of Ge 4+ When doped, the matrix maintains a single crystalline phase, avoiding the precipitation of impurity phases. This structural compatibility allows Ge 4 + A large number of substitutions in the lattice without destroying the long-range order, thus achieving Ce 3+ Effective control of energy levels and oxygen vacancies. 4+ When the doping concentration is ≤10%, a small amount of Ge 4+ (ion radius 0.039nm) replaces Si 4+ (ionic radius 0.026 nm), the lattice parameter changes slightly, Ce 3+ The surrounding ligand field strength does not change significantly, and its 5d energy level position is close to that of pure silicate system. When the concentration is ≥15%, a large amount of Ge 4+ The introduction of lattice expansion (Ge 4+ The ionic radius is larger, which increases the lattice constant), Ce 3+ The coordination environment of the ligand (O 2- )-Ce 3+ The average bond length increases, the crystal field splitting decreases, the 5d energy level decreases overall, and the emission wavelength redshifts. This redshift reduces phonon-assisted non-radiative relaxation, thereby significantly enhancing thermal stability and scintillation efficiency.

[0009] In the silicate matrix, oxygen vacancies usually act as electron traps, reducing the scintillation performance (such as prolonging the afterglow and reducing the ability to resist radiation damage). 4+ When doped, Ge 4+ With Si 4+ The substitutional doping does not significantly change the bonding environment of oxygen atoms, and the oxygen vacancy formation energy is low, which is easy to accumulate in the lattice. 4+ When doped, Ge 4+ With O 2- Forming a stronger covalent bond (Ge-O bond energy is higher than Si-O bond), and Ge 4+ The high coordination demand (possibly forming [GeO6] octahedra or distorted tetrahedra) forces oxygen atoms in the lattice to be packed more tightly, increasing the formation energy of oxygen vacancies and thermodynamically suppressing their generation. Effective suppression of oxygen vacancy traps significantly improves the radiation resistance of scintillating materials, reduces afterglow levels, and increases scintillation light output.

[0010] Preferably, 0.0001≤x≤0.003, 0.2≤y≤0.3.

[0011] Preferably, the rare earth element is Lu or Y or a solid solution of the two. More preferably, the rare earth element is a solid solution of Lu and Y, and more preferably Lu:Y=(7-9):1.

[0012] Preferably, the rare earth germanosilicate scintillating material with high thermal stability and strong radiation resistance is rare earth germanosilicate scintillating polycrystalline powder, rare earth germanosilicate scintillating ceramic, or rare earth germanosilicate scintillating single crystal.

[0013] According to a second aspect of the present invention, there is provided a method for preparing the rare earth germanosilicate scintillating material according to any one of the first aspects of the present invention, wherein the rare earth germanosilicate scintillating material is a rare earth germanosilicate scintillating polycrystalline powder, and the preparation method comprises the following steps:

[0014] S1. Dry the raw materials RE2O3 (RE is any one of La, Lu, Y, Gd), CeO2, SiO2, GeO2, and prepare the products according to the general formula RE 2(1-x-δ / 2) Ce 2x Ge δ Si (1-y+δ) Ge y-δ O z The molar ratio of each element is weighed and mixed to obtain a mixed powder;

[0015] S2. subjecting the mixed powder obtained in step S1 to a solid phase reaction at 1000-2000° C. for 5-200 hours to obtain a rare earth germanosilicate scintillating polycrystalline powder.

[0016] According to a third aspect of the present invention, there is provided a method for preparing the rare earth germanosilicate scintillating material according to any one of the first aspects of the present invention, wherein the rare earth germanosilicate scintillating material is a rare earth germanosilicate scintillating ceramic, and the preparation method comprises the following steps:

[0017] M1. Dry the raw materials RE2O3 (RE is selected from at least one of La, Lu, Y, Gd), CeO2, SiO2, and GeO2, and prepare the product according to the general formula RE 2(1-x-δ / 2) Ce 2x Ge δ Si (1-y+δ) Ge y-δ O z The elements are weighed and mixed in a molar ratio, and pressed into shape at a pressure of 0.03 GPa to 5 GPa.

[0018] M2. The mixed powder pressed in step M1 is subjected to a solid phase reaction at 1000-2000° C. for 5-200 hours to obtain rare earth germanosilicate scintillating ceramics.

[0019] According to a fourth aspect of the present invention, there is provided a method for preparing the rare earth germanosilicate scintillating material according to any one of the first aspects of the present invention, wherein the rare earth germanosilicate scintillating material is a rare earth germanosilicate scintillating single crystal, and the preparation method comprises the following steps:

[0020] N1, dry the raw materials RE2O3 (RE is selected from any one of La, Lu, Y, Gd), CeO2, SiO2, GeO2, and make them into 2(1-x-δ / 2) Ce 2x Ge δ Si (1-y+δ) Ge y-δ O z The molar ratio of each element is weighed and mixed to obtain a mixed powder; the mixed powder is pressed by cold isostatic pressing (pressure is 0.03~5 GPa), and after pressing and forming, the mixed powder is subjected to solid phase reaction at 1000~2000℃ for 5~200 hours to obtain a polycrystalline rod.

[0021] N2. The polycrystalline rod obtained in step N1 is heated to melt, and the rare earth germanium silicate scintillating single crystal is grown by using a Czochralski method, a crucible descent method, a temperature gradient method, a heat exchange method, a kyropoiesis method, a top seeding method, a horizontal directional solidification method, a flux crystal growth method or a micro-pull-down method.

[0022] According to a fifth aspect of the present invention, there is provided an application of the rare earth germanosilicate scintillating material with high thermal stability and strong radiation resistance as described in any one of the first aspects of the present invention.

[0023] Preferably, the radiation detection field includes high energy physics detection and particle identification, nuclear medicine imaging, oil well logging and geological exploration.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention introduces high concentration of Ge into the rare earth orthosilicate system. 4+ ions (≥15%), forming a solid solution rare earth germanosilicate, using Ge 4+ With Si 4+ The difference in ionic radius and the compatibility of the same space group structure achieve the coordinated optimization of scintillation performance: on the one hand, the luminous efficiency and thermal stability are improved through lattice engineering. 4+ Large-scale replacement of Si 4 ⁺ causes lattice expansion. This structural perturbation reconstructs the coordination environment of the Ce³⁺ activation center. This not only causes its 5d energy level to drop, causing a red shift in luminescence, but also effectively suppresses phonon-assisted non-radiative transitions, ultimately significantly increasing the thermal quenching activation energy. This is reflected in the performance of the material of the present invention. The thermal quenching onset temperature T 10 It is stable above 400 K (the comparison is about 360-370 K), and is capable of detecting tasks in high-temperature environments.

[0026] On the other hand, the durability and reliability of the material are improved by defect suppression. 4+ The formation energy of oxygen vacancies can be significantly increased from a thermodynamic perspective. Since oxygen vacancies are the main trap defects that cause afterglow and radiation damage, suppressing their generation at the source directly leads to a leap in performance: the afterglow level of the material is less than 0.18% after 300 seconds, and the light output loss is less than 6% after withstanding 100 kGy strong irradiation. Both of these indicators are far superior to those without high-concentration Ge 4+ Doped comparative sample (afterglow > 0.2%, irradiation loss > 10%).

[0027] The above effects are due to Ge 4+ Ce induced by high concentration doping 3+ The synergistic effect of altering the coordination environment and defect control overcomes the performance bottleneck of low-doping concentrations, achieving coordinated optimization of scintillation light output, afterglow, radiation resistance, and thermal stability. Therefore, the rare earth germanosilicate scintillating material obtained by this invention is well-suited for applications requiring high thermal stability or radiation resistance, such as high-energy physics detection and particle identification, nuclear medicine imaging, oil well logging, and geological exploration. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The graph shows how the X-ray excited luminescence intensity integral of the rare earth germanosilicate scintillating materials prepared in Comparative Example 1, Comparative Example 2 and Example 1 changes with temperature.

[0029] Figure 2The gamma-ray pulse height spectra of the rare-earth silicon germanate scintillation materials prepared in Comparative Example 1 (a), Comparative Example 2 (b), and Example 1 (c) before and after being subjected to strong irradiation are shown.

[0030] Figure 3 The gamma-ray pulse height spectra of the rare-earth silicon germanate scintillation materials prepared in Comparative Example 1 and Example 1 are shown.

[0031] Figure 4 The measurement results of the scintillation afterglow of the rare-earth silicon germanate scintillation materials prepared in Comparative Example 1 and Example 1 after being excited by X-rays are shown.

[0032] Figure 5 The X-ray excitation emission spectra of the rare-earth silicon germanate scintillation materials prepared in Comparative Example 1 and Example 1 are shown.

[0033] Figure 6 The thermoluminescence spectra of the rare-earth silicon germanate scintillation materials prepared in Comparative Example 1 and Example 1 after being excited by X-rays are shown. <00,00305> Figure 7 The X-ray diffraction spectra of the rare-earth silicon germanate scintillation materials prepared in Comparative Example 1 and Example 1 are shown. Detailed implementation manners

[0035] The present invention is further illustrated by the following implementation manners. It should be understood that the following implementation manners are only used to illustrate the present invention and do not limit the present invention.

[0036] The rare-earth silicon germanate scintillation material provided by the present invention, which belongs to the monoclinic system, has the chemical formula: RE 2(1-x-δ / 2) Ce 2x Ge δ Si (1-y+δ) Ge y-δ O z , where: 2(1 - x - δ / 2) is the content of the matrix RE 3+ (rare-earth ion), 2x is the content of the doped ion Ce 3+ (0 < x ≤ 0.​​​​​​​Taking into account the possible presence of oxygen vacancies or interstitial spaces in materials prepared under different atmospheres, the value of z ranges from 4.95 ≤ z ≤ 5.05. In the examples, the ingredients were designed based on z = 5. However, due to technical limitations, the true value of z is difficult to accurately quantify. It is generally believed that 4.95 ≤ z < 5 is acceptable for preparation under inert atmosphere, and 5 ≤ z ≤ 5.05 is acceptable for preparation under air or oxygen atmosphere.

[0037] The matrix ion RE is a rare earth ion, selected from at least one of lanthanum (La), lutetium (Lu), yttrium (Y), and gadolinium (Gd), preferably lutetium (Lu) or yttrium (Y) or a solid solution of the two, among which the most preferred is a solid solution of lutetium (Lu) and yttrium (Y), and the ratio of lutetium (Lu) to yttrium (Y) is (7~9):1.

[0038] In an optional embodiment, the rare earth germanosilicate scintillating material with high thermal stability and strong radiation resistance is a polycrystalline powder, ceramic, or single crystal.

[0039] In the present invention, during the preparation of rare earth germanosilicate scintillating materials with high thermal stability and strong radiation resistance, a very small amount of the doping element Ge may be doped into the RE site. However, due to technical limitations, conventional characterization methods are difficult to determine its accurate doping content, and the doping of a very small amount of the doping element Ge into the RE site will not cause any essential change in the performance of the material itself. Therefore, δ is generally considered to be ≈0.

[0040] The following is an exemplary method for preparing the rare earth germanosilicate scintillating material with high thermal stability and strong radiation resistance provided by the present invention. The resulting rare earth germanosilicate scintillating material is a polycrystalline powder, ceramic, or single crystal. The ceramic can be transparent or non-transparent. The preparation method is as follows:

[0041] S1: Preparation of mixed powder

[0042] Rare earth oxide RE2O3 (RE is selected from any at least one of La, Lu, Y, and Gd) and CeO2, SiO2, and GeO2 are used as raw materials, and are proportioned according to the molar amounts of the raw material components and then fully mixed to obtain a mixed powder.

[0043] S2-1: Preparation of polycrystalline powder

[0044] The mixed powder obtained in step S1 is directly subjected to a solid phase reaction at 1000-2000° C. for 5-200 hours to obtain polycrystalline powder, wherein the temperature of the solid phase reaction can be further controlled at 1300-1600° C., and the time can be further controlled at 10-50 hours.

[0045] S2-2: Preparation of ceramics

[0046] The mixed powder obtained in step S1 is pressed into a block under a pressure of 0.03 to 5 GPa, and sintered at 1000-2000°C for 5 to 200 hours to obtain a ceramic. Alternatively, a sintering process can be controlled to produce a transparent ceramic. Specifically, a sintering process such as hot pressing or vacuum sintering can be used to produce the transparent ceramic. The sintering temperature can be further controlled to 1300-1600°C, the sintering time can be further controlled to 10 to 50 hours, and the pressure for pressing the block is preferably 2 to 3 GPa.

[0047] S3-3: Preparation of single crystals

[0048] At least one of the polycrystalline powder obtained in step S2-1, the powder obtained by grinding the transparent ceramic obtained in step S2-2, and the mixed powder obtained in step S1 is placed in a container as a raw material and pressed by cold isostatic pressing. After pressing, the polycrystalline rod is subjected to solid-state reaction at 1000-2000°C for 5-200 hours to obtain the polycrystalline rod. The cold isostatic pressing pressure is 0.03-5 GPa. The polycrystalline rod is melted by heating (e.g., resistance, electromagnetic induction, or light), and slowly crystallized from the melt to produce a single crystal. Specific methods include Czochralski pulling, crucible drop method, temperature gradient method, heat exchange method, Kyropoulos method, top seeding method, horizontal directional solidification method, flux crystal growth method, or micro-pull-down method. Preferably, the micro-pull-down method is used to grow the single crystal at a pull-down rate of 5-20 mm / h. More preferably, the Czochralski method is used to grow the single crystal, with the pull-down method being rotational and at a pull rate of 1-10 mm / h and a rotation speed of 1-50 r / min.

[0049] The present invention provides a rare earth germanosilicate scintillating material with high thermal stability and strong radiation resistance, wherein Ge 4+ Ce induced by high concentration doping 3+ The synergistic effect of altering the coordination environment and defect control overcomes the performance bottleneck of low-doping concentrations, significantly improving both radiation damage resistance and thermal quenching resistance, reducing afterglow while increasing scintillation light output. The highly thermally stable and radiation-resistant rare earth germanosilicate scintillating material provided by this invention can be widely used in applications requiring high radiation resistance or thermal quenching resistance, such as high-energy physics detection and particle identification, nuclear medicine imaging, oil well logging, and geological exploration.

[0050] The following examples are further listed to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention all fall within the scope of protection of the present invention. The specific process parameters and the like in the following examples are only examples within a suitable range, that is, those skilled in the art can select within a suitable range through the description herein, and are not limited to the specific numerical values ​​exemplified below.

[0051] Example 1

[0052] The pulling method is used to grow scintillating single crystals. Specifically, the ingredients are mixed in a molar ratio of Lu2O3:Y2O3:CeO2:SiO2:GeO2 =0.898:0.1:0.004:0.7:0.3. After being fully mixed, the mixture is pressed into a rod by cold isostatic pressing (pressure of 0.3GPa). After the rod is solid-phase reacted at 1600°C in a muffle furnace for 50 hours, a polycrystalline block (i.e., a polycrystalline rod) is obtained. The polycrystalline rod is transferred to an iridium crucible and placed in a crystal growth furnace. With nitrogen as the protective atmosphere, the polycrystalline rod is melted by medium-frequency induction heating and kept warm until all components are fully reacted. After seeding, a single crystal of a preset size is slowly pulled out from the melt to obtain Lu 1.796 Y 0.2 Ce 0.004 Si 0.7 Ge 0.3 O5 single crystal. The parameters of the Czochralski method include a pulling speed of 1-10 mm / h and a rotation speed of 15-30 r / min.

[0053] Example 2

[0054] In this embodiment, Lu 1.75 Y 0.2 Ce 0.05 Si 0.7 Ge 0.3 The preparation process of O5 single crystal refers to Example 1, except that in Example 2, the ingredients are prepared according to the molar ratio of Lu2O3:Y2O3:CeO2:SiO2:GeO2 =0.875:0.1:0.05:0.7:0.3, that is, the added amount of Ce is 2.5%.

[0055] Example 3

[0056] In this embodiment, Lu 1.7 Y 0.2 Ce 0.1 Si 0.7 Ge 0.3 The preparation process of O5 single crystal is similar to that of Example 1, except that in Example 3, the ingredients are prepared in a molar ratio of Lu2O3:Y2O3:CeO2:SiO2:GeO2 = 0.85:0.1:0.1:0.7:0.3, that is, the amount of Ce added is 5%.

[0057] Example 4

[0058] In this embodiment, La 1.996 Ce 0.004 Si 0.7 Ge 0.3The preparation process of O5 single crystal is similar to that of Example 1, except that in Example 4, the ingredients are prepared in a molar ratio of La2O3:CeO2:SiO2:GeO2 = 0.998:0.004:0.7:0.3, that is, the rare earth element is only La.

[0059] Example 5

[0060] In this embodiment, Gd 1.996 Ce 0.004 Si 0.7 Ge 0.3 The preparation process of O5 single crystal is similar to that of Example 1, except that in Example 5, the ingredients are prepared in a molar ratio of Gd2O3:CeO2:SiO2:GeO2 = 0.998:0.004:0.7:0.3, that is, the rare earth element is only Gd.

[0061] Example 6

[0062] In this embodiment, Lu 1.996 Ce 0.004 Si 0.7 Ge 0.3 The preparation process of O5 single crystal is similar to that of Example 1, except that in Example 6, the ingredients are prepared in a molar ratio of Lu2O3:CeO2:SiO2:GeO2 = 0.998:0.004:0.7:0.3, that is, the rare earth element is only Lu.

[0063] Example 7

[0064] In this embodiment, Y 1.996 Ce 0.004 Si 0.7 Ge 0.3 The preparation process of the O5 single crystal is similar to that of Example 1, except that in Example 7, the ingredients are prepared in a molar ratio of Y2O3:CeO2:SiO2:GeO2 = 0.998:0.004:0.7:0.3, that is, the rare earth element is only Y.

[0065] Example 8

[0066] In this embodiment, La 0.3 Lu 1.496 Y 0.2 Ce 0.004 Si 0.7 Ge 0.3 The preparation process of O5 single crystal refers to Example 1, except that in this Example 8, the ingredients are prepared in a molar ratio of La2O3:Lu2O3:Y2O3:CeO2:SiO2:GeO2 =0.15:0.748:0.1:0.004:0.7:0.3, that is, the rare earth elements are a combination of La, Lu and Y.

[0067] Comparative Example 1

[0068] In this comparative example 1, Lu 1.796 Y 0.2 Ce 0.004 The preparation process of SiO5 single crystal is referred to Example 1, except that in this comparative example 1, the molar ratio of Lu2O3:Y2O3:CeO2:SiO2 is 0.898:0.1:0.004:1, i.e. Ge 4+ The addition amount is 0at.%.

[0069] Comparative Example 2

[0070] In this comparative example 2, Lu 1.796 Y 0.2 Ce 0.004 Si 0.9 Ge 0.1 The preparation process of O5 single crystal refers to Example 1, except that in this comparative example 2, the molar ratio of Lu2O3:Y2O3:CeO2:SiO2:GeO2 is 0.898:0.1:0.004:0.9:0.1, that is, Ge 4+ The addition amount is 10 at.%.

[0071] Example 9

[0072] The micro-pull-down method (μ-PD) is used to grow scintillating single crystals. Specifically, the molar ratio of Lu2O3:Y2O3:CeO2:SiO2:GeO2=0.8995:0.1:0.001:0.85:0.15 is used. After being fully mixed, the material is pressed into a block and placed in a muffle furnace at 1600°C for solid phase reaction for 20 hours. The polycrystalline block is then transferred to an iridium crucible and melted by high-frequency induction heating under a protective atmosphere. The temperature is kept until all components react fully. Nitrogen is used as a protective atmosphere, and the induction heating is used to fully melt. After the seed crystal contacts the melt, it is slowly pulled down to obtain Lu 1.799 Y 0.2 Ce 0.001 Si 0.85 Ge 0.15 O5 single crystal, wherein the parameters of the micro-pull-down method include: an iridium crucible having a channel with an inner diameter of 1 mm and an outer diameter of 2-5 mm, and a pull-down speed of 10-15 mm / h.

[0073] Example 10

[0074] In this embodiment 10, Lu 1.799 Y 0.2 Ce 0.001 Si 0.8 Ge 0.2The preparation process of O5 single crystal is referred to Example 9, except that in Example 10, the molar ratio of Lu2O3:Y2O3:CeO2:SiO2:GeO2 is 0.8995:0.1:0.001:0.8:0.2, i.e. Ge 4+ The addition amount is 20 at.%.

[0075] Example 11

[0076] In this embodiment 11, Lu 1.799 Y 0.2 Ce 0.001 Si 0.7 Ge 0.3 The preparation process of O5 single crystal is referred to Example 9, except that in Example 11, the molar ratio of Lu2O3:Y2O3:CeO2:SiO2:GeO2 is 0.8995:0.1:0.001:0.7:0.3, i.e. Ge 4+ The addition amount is 30 at.%.

[0077] Example 12

[0078] In this embodiment 12, Lu 1.799 Y 0.2 Ce 0.001 Si 0.6 Ge 0.4 The preparation process of O5 single crystal is referred to Example 9, except that in Example 12, the molar ratio of Lu2O3:Y2O3:CeO2:SiO2:GeO2 is 0.8995:0.1:0.001:0.6:0.4, i.e. Ge 4+ The addition amount is 40 at.%.

[0079] Example 13

[0080] In this embodiment 13, Lu 1.799 Y 0.2 Ce 0.001 Si 0.5 Ge 0.5 The preparation process of O5 single crystal is referred to Example 9, except that in Example 13, the molar ratio of Lu2O3:Y2O3:CeO2:SiO2:GeO2 is 0.8995:0.1:0.001:0.5:0.5, i.e. Ge 4+ The addition amount is 50 at.%.

[0081] Comparative Example 3

[0082] In this comparative example 3, Lu 1.799 Y 0.2 Ce 0.001The preparation process of SiO5 single crystal refers to Example 9, except that in this comparative example 3, the molar ratio of Lu2O3:Y2O3:CeO2:SiO2 is 0.8995:0.1:0.001:1, that is, Ge 4+ The addition amount is 0at.%.

[0083] Comparative Example 4

[0084] In this comparative example 4, Lu 1.799 Y 0.2 Ce 0.001 Si 0.99 Ge 0.01 The preparation process of O5 single crystal refers to Example 9, except that in this comparative example 4, the molar ratio of Lu2O3:Y2O3:CeO2:SiO2:GeO2 is 0.8995:0.1:0.001:0.99:0.01, i.e. Ge 4+ The addition amount is 1 at.%.

[0085] Comparative Example 5

[0086] In this comparative example 5, Lu 1.799 Y 0.2 Ce 0.001 Si 0.9 Ge 0.1 The preparation process of O5 single crystal refers to Example 9, except that in this comparative example 5, the molar ratio of Lu2O3:Y2O3:CeO2:SiO2:GeO2 is 0.8995:0.1:0.001:0.9:0.1, i.e. Ge 4+ The addition amount is 10 at.%.

[0087] Example 14

[0088] The scintillating polycrystalline powder was prepared by solid phase sintering method. Specifically, the molar ratio of Lu2O3:Y2O3:CeO2:SiO2:GeO2 was 0.898:0.1:0.004:0.7:0.3. After being fully mixed, the mixture was placed in a muffle furnace at 1600℃ for solid phase reaction for 20 hours to obtain Lu 1.796 Y 0.2 Ce 0.004 Si 0.7 Ge 0.3 O5 polycrystalline powder.

[0089] Example 15

[0090] Preparation of scintillating ceramics. The ingredients were mixed in a molar ratio of Lu2O3:Y2O3:CeO2:SiO2:GeO2 = 0.898:0.1:0.004:0.7:0.3, and after thorough mixing, the mixture was pressed into a block at 0.3 GPa cold isostatic pressing, placed in a corundum crucible, and placed in a vacuum furnace for solid phase reaction at 1600℃ for 20 hours to obtain Lu 1.796 Y 0.2 Ce 0.004 Si 0.7 Ge 0.3 O5 transparent shimmering ceramic.

[0091] Performance testing:

[0092] 1. Thermal quenching resistance test

[0093] To investigate the thermal quenching resistance of scintillating materials, radioluminescence spectra were measured using a spectrophotometer (FLS980, Edinburgh) equipped with an X-ray source (Mini-X, Amptek) in a liquid nitrogen cryostat (temperature range 77 K–500 K). The integrated intensity extracted from the radioluminescence spectrum in the wavelength range of 350–700 nm was plotted as a function of temperature. The integrated X-ray-stimulated luminescence intensity decreased significantly with increasing ambient temperature, and the temperature at which the integrated intensity decreased by 10% was defined as the quenching onset temperature, T. 10 .

[0094] 2. Radiation resistance test

[0095] In order to study the radiation resistance of scintillating materials, we used 60 Using a Co γ-ray source, scintillator samples were irradiated with γ-rays for 10 hours at an average dose rate of 15.83 ± 0.66 kGy / h. Radiation damage to the scintillator was characterized by comparing light output before and after irradiation.

[0096] 3. Flashing light output performance test

[0097] To study the scintillation light output of scintillating materials, use 137 Pulse height spectra were collected using a Hamamatsu R878 photomultiplier tube using a Cs gamma-ray source. Gaussian fits were performed to the full-energy peak, and the channel number was recorded. Relative light output was calculated by comparison with a LYSO:Ce single crystal calibrated using the single-electron peak method (channel number 725, light output 33,000 ph / MeV).

[0098] 4. Afterglow level performance test

[0099] Afterglow curves were measured using a spectrophotometer (FLS980, Edinburgh) equipped with an X-ray source (Mini-X, Amptek). Prior to afterglow measurements, all crystals were irradiated with X-rays continuously for 180 s at 49 kV and 80 μA. This test was performed at room temperature.

[0100] Table 1 shows the performance test results of the above embodiments and comparative examples.

[0101] Table 1

[0102]

[0103] Combined with Table 1, it can be seen that the rare earth germanosilicate scintillating single crystals (pulling method and micro-pull-down method) with high concentration Ge4+ ion substitution (≥15%) obtained by different preparation methods, scintillating polycrystalline powder, and scintillating ceramics all have significantly improved resistance to radiation damage and thermal quenching.

[0104] From the experimental data of Comparative Examples 1 to 5, it can be seen that RE in Comparative Examples 1 and 2 are both selected from Lu, Y, and Ce. 3+ Atomic fraction = 0.2 at.%, the difference is that in comparative example 2, Ge 4+ The atomic fraction is 10%, and comparative example 1 is not doped with Ge. It can be seen that the scintillation light output, afterglow level, radiation resistance and thermal stability of comparative example 2 are all improved compared with the undoped comparative example 1; similarly, RE of comparative examples 3 to 5 are all selected from Lu, Y, and Ce. 3+ Atomic fraction = 0.05 at.%, the difference is that comparative example 3 is not doped with Ge, and comparative example 4 has Ge 4+ The atomic fraction is 1%, and Ge in Comparative Example 5 4+ The atomic fraction is 10%. It can be seen that the scintillation light output, afterglow level, radiation resistance and thermal stability of Comparative Examples 4 and 5 are all improved compared with the undoped Comparative Example 3. This shows that when Ge 4+ When the atomic fraction is greater than 0, the scintillation light output, afterglow level, radiation resistance and thermal stability of the crystal can be improved. However, combined with the specific test data of Comparative Examples 2, 4 and 5, it can be seen that in Ge 4+ When the atomic fraction is ≤10%, the improvement of crystal scintillation performance is small, that is, the scintillation light output is lower than 33000 ph. / MeV, the light output loss ratio after irradiation is greater than or equal to 10%, the afterglow level is greater than 0.20%@300 s, and the quenching onset temperature T 10 Less than 373 K.

[0105] Further combined with the experimental data of Example 1 and Examples 9 to 13, compared with Comparative Example 2, Example 1 and Comparative Example 2 have the RE selected from Lu and Y, and Ce 3+ Atomic fraction = 0.2 at.%, the difference between the two is that the Ge 4+ The atomic fraction is 30%, while the Ge 4+ The atomic fraction is 10%. Compared with the comparative example 2, the scintillation performance of Example 1 is greatly improved, that is, the scintillation light output reaches 35,900 ph. / MeV, the scintillation light output is improved, and the thermal quenching starting temperature T 10 The temperature reaches 409K, the afterglow level is 0.07%@300s, and the light output loss ratio is 3.9% after ≥100 kGy strong irradiation; at the same time, compared with comparative examples 4 and 5, the RE of Examples 9 to 13 are all selected from Lu, Y, and Ce. 3+ Atomic fraction = 0.05 at.%, the difference between Examples 9 to 13 and Comparative Examples 4 and 5 is that the Ge 4+ The atomic fractions are all ≤10%, while the Ge 4+ The atomic fractions are all ≥15% and ≤50%. Compared with Comparative Examples 4 and 5, the experimental data of Examples 9 to 13 show that when Ge 4+ When the atomic fraction is ≥15% (and ≤50%), the corresponding scintillation performance is greatly improved, that is, the scintillation light output is greater than 33,000 ph. / MeV, the scintillation light output is improved and the thermal quenching starting temperature of the material T 10 ≥400 K, afterglow level ≤ 0.18%@300 s, and light output loss ratio ≤ 6% after strong irradiation ≥100 kGy.

[0106] Furthermore, it can be seen from Examples 1, 4 to 8 that the high concentration Ge obtained by using different rare earth elements defined in this application 4+ The ion-substituted rare earth germanosilicate scintillating single crystals have significantly improved resistance to radiation damage and thermal quenching; from Examples 1 to 3, it can be seen that the different contents of Ce defined in this application are used. 3+ The resulting high concentration Ge 4+ The ion-substituted rare earth germanosilicate scintillating single crystals have significantly improved resistance to radiation damage and thermal quenching; from Examples 9 to 13, it can be seen that the different high concentrations of Ge defined in this application are used. 4+ Ion-substituted rare earth germanosilicate scintillating single crystals have significantly improved resistance to radiation damage and thermal quenching.

[0107] In addition, it can be seen from Examples 1 and 4 to 8 that when the matrix ion RE is selected from lutetium (Lu) or yttrium (Y) or a solid solution of the two, the effect is better, especially when it is selected from a solid solution of lutetium (Lu) and yttrium (Y), the effect is optimal.

[0108] Figure 1 The X-ray excitation luminescence intensity integral of the rare earth germanosilicate scintillating single crystal prepared in Comparative Example 1, Comparative Example 2 and Example 1 is shown as a function of temperature. 4+ The thermal quenching resistance is significantly improved. At room temperature of 300 K, the integrated luminescence intensity of Comparative Example 1, Comparative Example 2, and Example 1 remains at 94%, 97%, and 98% of that at 80 K, respectively, indicating that the luminescence of all samples is relatively stable in the range of 80 K to room temperature. As mentioned above, the integrated luminescence intensity of X-ray excitation decreases significantly with the increase of ambient temperature. The temperature at which the intensity integral decreases by 10% is defined as the quenching onset temperature T 10 It can be seen that the quenching onset temperatures of Comparative Example 1, Comparative Example 2 and Example 1 are 359 K, 370 K and 409 K, respectively. The activation energy E related to the thermal quenching process a These can be approximately estimated to be 0.4316 eV, 0.4381 eV, and 0.5594 eV using a specific Arrhenius equation.

[0109] Figure 2 Figures 1 and 2 show the gamma-ray pulse height spectra of the rare earth germanosilicate scintillating single crystals prepared in Comparative Example 1 (a), Comparative Example 2 (b), and Example 1 (c) before and after intense irradiation. For all scintillators, light output decreased after intense irradiation compared to pre-irradiation levels. Light output in Comparative Example 1, Comparative Example 2, and Example 1 decreased to 88.4%, 90.0%, and 96.1%, respectively, demonstrating that the rare earth germanosilicate scintillating single crystal provided in Example 1 has enhanced resistance to radiation damage.

[0110] Figure 3 The gamma-ray pulse height spectra of the rare earth germanosilicate scintillating materials obtained in Comparative Example 1 and Example 1 are given. Figure 3 It can be seen that the introduction of Ge 4+ The number of channels of post-characterization crystal light output increased from 684 in Comparative Example 1 to 780, significantly improving scintillation light output. Compared to a LYSO:Ce single crystal calibrated using the single electron peak method (725 channels and a light output of 33,000 ph. / MeV), the absolute light output was calculated: 32,000 ph. / MeV for Comparative Example 1 and 35,900 ph. / MeV for Example 1.

[0111] Figure 4 The scintillation afterglow measurement results of the rare earth germanosilicate scintillating materials prepared in Comparative Example 1 and Example 1 after being excited by X-rays are given. Figure 4It can be seen that the rare earth germanosilicate scintillating single crystal provided in Example 1 has a faster afterglow decay, which drops to 0.07% within 300 seconds after the X-ray stops, indicating the excellent low afterglow performance of the crystal.

[0112] In order to determine the introduction of high concentration Ge 4+ Post-Ce 3+ Changes in coordination environment, use and Figure 1 The same setup was tested to measure the room temperature X-ray excitation emission spectrum. Figure 5 The X-ray excitation emission spectra of the rare earth germanosilicate scintillating single crystals prepared in Comparative Example 1 and Example 1 are given. Figure 5 It can be seen that the introduction of high concentration Ge 4+ Afterwards, Ce 3+ The emission peak shifts significantly toward the long-wave direction. This red shift reduces the probability of non-radiative relaxation of 5d excited state electrons, thereby significantly enhancing thermal stability and scintillation efficiency.

[0113] In order to determine the introduction of Ge 4+ The changes in carrier traps related to the scintillation performance are analyzed using the Figure 1 The same setup was used to measure thermoluminescence spectroscopy. The sample was first preheated to eliminate trapped charge carriers and then irradiated with X-rays at 77 K. -1 Thermoluminescence spectroscopy measurements were achieved by linearly heating the cryostat at a rate of 100 nm. Figure 6 The thermoluminescence spectra of the rare earth germanosilicate scintillating single crystals prepared in Comparative Example 1 and Example 1 after X-ray excitation are given. Figure 6 It can be seen that the introduction of Ge 4+ After the addition of oxygen vacancy, the intensities of the two thermoluminescence peaks above room temperature are significantly reduced, indicating that the carrier traps associated with them are significantly suppressed. In rare earth orthosilicates, the traps corresponding to the peaks at 373 K and 436 K in the thermoluminescence curve are highly correlated with oxygen vacancy defects and are believed to be the cause of reduced resistance to radiation damage, loss of light output, and enhanced afterglow. Benefiting from the lower oxygen vacancy defect concentration, rare earth germanosilicate scintillating single crystals exhibit enhanced resistance to radiation damage, increased scintillation light output, and lower afterglow levels.

[0114] In order to prove the phase composition of the rare earth germanosilicate scintillating single crystal, the X-ray diffraction spectra of the rare earth germanosilicate scintillating materials prepared in Comparative Example 1 and Example 1 were obtained by X-ray diffractometer. Figure 7 It can be seen that compared with the LYSO:Ce material of Comparative Example 1, the diffraction peak of the germanosilicate material of Example 1 can be seen through (Lu 1.81 Y 0.19)SiO5 structure matches (PDF#97-015-9308), and there is no impurity peak. This shows that its structure is consistent with (Lu 1.81 Y 0.19 )SiO5 is the same. 4+ Radius 40pm, Ge 4+ Radius 53 pm, rare earth RE 3+ Ionic radius > 100 pm, Ge 4+ It mainly occupies silicon lattice sites, so the X-ray diffraction peak shifts to lower angles, indicating that the unit cell volume becomes larger.

[0115] In summary, the rare earth germanosilicate scintillating material provided in the embodiment of the present invention has stronger resistance to thermal quenching and radiation damage than the rare earth orthosilicate scintillating material, and takes into account high light output and low afterglow. It can meet the higher requirements of high-energy physics experiments, nuclear medicine imaging, and oil well exploration for the material's resistance to thermal quenching, radiation resistance, high light output, and low afterglow properties.

[0116] Through the above embodiments, combined with different compositions and different processes, the highly thermally stable and radiation-resistant rare earth germanium silicate scintillating material of the present application can be prepared.

[0117] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A rare earth germanium silicate scintillating material with high thermal stability and strong radiation resistance, characterized in that: The general formula of the scintillating material is RE 2(1-x-δ / 2) Ce 2x Ge δ Si (1-y+δ) Ge y-δ O z , where: 0 <x≤0.05,0.15≤y≤0.5,0≤δ≤10 -4 , and 4.95≤z≤5.05, RE is one or more combinations of La, Lu, Y, and Gd.

2. The rare earth germanium silicate scintillating material with high thermal stability and strong radiation resistance according to claim 1, characterized in that: 0.0001≤x≤0.003, 0.2≤y≤0.

3.

3. The rare earth germanium silicate scintillating material with high thermal stability and strong radiation resistance according to claim 1, characterized in that: The RE is a solid solution of Lu and Y, wherein Lu:Y=(7~9):

1.

4. The rare earth germanium silicate scintillating material with high thermal stability and strong radiation resistance according to claim 1, characterized in that: The rare earth germanosilicate scintillating material is rare earth germanosilicate scintillating polycrystalline powder, rare earth germanosilicate scintillating ceramic, or rare earth germanosilicate scintillating single crystal.

5. A method for preparing the rare earth germanosilicate scintillating material according to any one of claims 1 to 4, characterized in that: The rare earth germanosilicate scintillating material is rare earth germanosilicate scintillating polycrystalline powder, and the method comprises the following steps: S1, dry the raw materials RE2O3, CeO2, SiO2, GeO2, and prepare the products according to the general formula RE 2(1-x-δ / 2) Ce 2x Ge δ Si (1-y+δ) Ge y-δ O z The molar ratio of each element is weighed and mixed to obtain a mixed powder, wherein RE is any at least one of La, Lu, Y, and Gd; S2. Subjecting the mixed powder obtained in step S1 to a solid phase reaction at 1000-2000° C. for 5-200 hours to obtain rare earth germanosilicate scintillating polycrystalline powder.

6. A method for preparing the rare earth germanosilicate scintillating material according to any one of claims 1 to 4, characterized in that: The rare earth germanosilicate scintillation material is rare earth germanosilicate scintillation ceramic, and the method comprises the following steps: M1, dry the raw materials RE2O3, CeO2, SiO2, GeO2, and prepare the products according to the general formula RE 2(1-x-δ / 2) Ce 2x Ge δ Si (1-y+δ) Ge y-δ O z The elements are weighed and mixed in a molar ratio, and pressed into a shape at a pressure of 0.03 GPa to 5 GPa, wherein RE is at least one of La, Lu, Y, and Gd; M2. Subjecting the pressed mixed powder obtained in step M1 to a solid phase reaction at 1000-2000° C. for 5-200 hours to obtain rare earth germanosilicate scintillating ceramics.

7. A method for preparing the rare earth germanosilicate scintillating material according to any one of claims 1 to 4, characterized in that: The rare earth germanosilicate scintillating material is a rare earth germanosilicate scintillating single crystal, and the method comprises the following steps: N1, dry the raw materials RE2O3, CeO2, SiO2, GeO2, and make them into 2(1-x-δ / 2) Ce 2x Ge δ Si (1-y+δ) Ge y-δ O z The molar ratio of each element in the mixture is weighed and mixed to obtain a mixed powder; cold isostatic pressing is performed, and after pressing and forming, solid phase reaction is carried out at 1000-2000°C for 5-200 hours to obtain a polycrystalline material rod; wherein RE is selected from any one of La, Lu, Y, and Gd, and the pressure of the cold isostatic pressing is 0.03-5 GPa; N2. Heat the polycrystalline rod obtained in step N1 until it is melted, and grow the rare earth germanium silicate scintillating single crystal by any one of the following methods: Czochralski method, crucible descent method, temperature gradient method, heat exchange method, kyropoiesis method, top seeding method, horizontal directional solidification method, flux crystal growth method, and micro-pull-down method.

8. Use of the rare earth germanosilicate scintillating material with high thermal stability and strong radiation resistance according to any one of claims 1 to 4 in the field of radiation detection.

9. The use of the rare earth germanosilicate scintillating material in the field of radiation detection according to claim 8, characterized in that: The radiation detection field includes high energy physics detection and particle identification, nuclear medicine imaging, oil well logging and geological exploration.

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