Ultrafast high-brightness extremely-low-fluorescence rare earth orthosilicate scintillation material and preparation method therefor

Abstract

The present invention provides an ultrafast high-brightness extremely-low-fluorescence rare earth orthosilicate scintillation material, a preparation method therefor, and a use thereof. The chemical formula of the ultrafast high-brightness extremely-low-fluorescence rare earth orthosilicate scintillation material is RE2(1-x-y-a)Ce2xCa2yA2aSi(1-z)AlzO5, wherein 0<x≤0.05, 0<y≤0.02, 0<z≤0.05, and 0≤a≤0.01; RE represents a rare earth element selected from among at least one of lanthanum, lutetium, yttrium and gadolinium; and A represents an additional doping element selected from among at least one of lithium Li, sodium Na, potassium K, rubidium Rb, cesium Cs, magnesium Mg, strontium Sr, scandium Sc, ytterbium Yb, and copper Cu. An ultrafast high-brightness extremely-low-fluorescence rare earth orthosilicate scintillation material according to an embodiment of the present invention can achieve a high light yield, rapid scintillation attenuation, and extremely low fluorescence response at a low doping concentration, facilitates engineered batch preparation, and has an anti-ultraviolet interference characteristic, so that no light shielding treatment is required during use and transportation processes; hence, the ultrafast high-brightness extremely-low-fluorescence rare earth orthosilicate scintillation material is an excellent material for detecting rays in a radiation and ultraviolet mixed field. In addition, due to the ultrafast high-brightness scintillation luminescence performance, said material can be widely applied to the fields of high-energy physical detection, particle discrimination and nuclear medical imaging.

Description

Ultrafast, high-brightness, and extremely low-fluorescence rare earth orthosilicate scintillating material and preparation method thereof Technical Field

[0001] The present invention relates to the technical field of scintillation materials, and in particular to an ultrafast, high-brightness, and extremely low-fluorescence rare earth orthosilicate scintillation material, and a preparation method and application thereof. Background Art

[0002] Inorganic scintillating materials are energy converters that can convert the energy carried by high-energy rays (X / gamma rays) or particles (protons, neutrons, etc.) into pulses in the ultraviolet-visible band. They are core sensitive elements for radiation detection and can be combined with photodetectors (which can convert ultraviolet-visible photons into electrical signals) to form scintillation detectors. The narrow temporal distribution of scintillation light pulses from ultrafast scintillation crystals results in radiation detectors using such crystals having ultrahigh temporal resolution and detection repetition rate. With the development of my country's manufacturing technology for large-scale high-end medical imaging equipment and key components, higher requirements are being placed on the resolution capabilities of ultrafast, high-brightness scintillation crystals used in key detection components in radiation detection systems.

[0003] Due to the high atomic number and complex extranuclear electronic structure of rare earth elements, the research and development of ultrafast scintillation crystals are mostly centered around rare earth or rare earth doped scintillation crystals. Currently, the ultrafast (rare earth) scintillation crystals that have been applied include BaF2, BaF2:Y, Y3Al5O 12 :Yb (YAG:Yb), ZnO:Ga, and PbWO4:Y (PWO:Y). However, despite their short decay times, these materials offer very low light yields. Consequently, existing ultrafast scintillating crystals are unable to meet the demands of new ultrafast detectors for critical applications such as major engineering projects and medical imaging equipment, necessitating the development of high-light-yield ultrafast scintillating crystals.

[0004] On the other hand, rare earth orthosilicate scintillating materials have high light yield. Rare earth orthosilicate scintillating materials include YSO:Ce, GSO:Ce, LSO:Ce and their solid solutions LYSO:Ce, LGSO:Ce and GYSO:Ce. Among them, LYSO:Ce scintillating crystal is currently the best candidate material for achieving ultrafast high scintillation luminescence. It is a monoclinic crystal with a space group of C2 / c. Lu / Y atoms have two coordination environments (RE1 and RE2) in the crystal, with coordination numbers of 7 and 6 respectively. RE1 and 5 [SiO4] O 2- and two isolated O atoms not bonded to silicon 2- Coordinate to form a distorted decahedron, RE2 and 4 [SiO4] O 2- and two isolated O atoms not bonded to silicon 2- Coordinate to form a pseudo-octahedron, the distorted [ORE4] tetrahedron is arranged parallel to the c-axis and is linked by [SiO4]. 3+As an activator, Ce 3+ The 5d→4f parity-allowed transitions give rise to high-intensity fast-decay luminescence.

[0005] However, rare earth orthosilicate scintillating materials, such as LYSO:Ce, have high light yields but long decay times. To accelerate the decay rate of LYSO:Ce crystals, Wu et al. (Crystal Growth & Design, 2019, 19(7):4081-4089; ACS Applied Materials & Interfaces, 2019, 11(8):8194-8201.) reported that Li + 、Cu 2+ Regarding the doping effect in Lu2SiO5:Ce, under low concentration doping, although the light yield is improved to a certain extent (about 20%), the flicker decay time is only accelerated by 1 to 3ns; under high concentration doping, although the decay time is significantly accelerated (from 45.4ns to 25.0ns), the light yield is greatly sacrificed (about 100 times).

[0006] Therefore, there is an urgent need to provide a scintillation material with high light yield and ultrafast scintillation. Summary of the Invention

[0007] In order to improve the scintillation attenuation of LYSO:Ce, studies on Ca co-doped LYSO:Ce materials have found that Ca co-doping does not change the energy level structure of Ce1 or Ce2, but reduces the amount of Ce2 relative to Ce1. The luminescence of LYSO:Ce is composed of a combination of 5d-4f transitions of the hepta-coordinated Ce1 and the hexa-coordinated Ce2 double lattice sites. The emission peaks at 393nm and 425nm are attributed to Ce1 luminescence, while the luminescence wavelength of Ce2 is longer (about 550nm). On this basis, the inventors have verified through a large number of experiments that Ce1 has higher luminescence efficiency and shorter decay time than Ce2. In other words, the luminescence of Ce2 is suppressed, which contributes to the rapid scintillation attenuation of Ca co-doped LYSO:Ce. However, Ca co-doped LYSO:Ce materials have photoluminescence properties. If they are exposed to ultraviolet light during use and transportation, they will generate extremely strong background noise during detection.

[0008] Further studies also found that Ca 2+ and Mg 2+ When divalent cations are co-doped at rare earth sites, in order to maintain the charge balance, a portion of Ce 3+ Will transform into stable Ce 4+ , which results in the formation of stable Ce in the lattice 4+ , whose scintillation emission process bypasses Ce 3+The initial hole capture process is slowed down and the charge carrier capture at the defect is suppressed, thereby improving the blinking time performance. 4+ The 4f ground state is empty and there is no 5d-4f emission under ultraviolet light excitation, which means that the stable Ce 4+ The higher the content, the lower the photoluminescence intensity. In other words, in order to improve the photoluminescence phenomenon, a large amount of stable Ce needs to be introduced. 4+ However, if a large amount of stable Ce is introduced simply by increasing the doping concentration of rare earth sites, 4+ , which will result in poor light yield.

[0009] On the other hand, Chinese patent application CN112630818A discloses a silicon lattice doping to improve rare earth orthosilicate scintillating material and its preparation method and application. The doping of silicon lattice can affect the activation center on the rare earth lattice through the oxygen ions and oxygen vacancies on [SiO4], and the low-valent cation doping may introduce Ce 4+ , thereby accelerating the decay time. However, in order not to greatly affect the scintillation decay performance and light yield, the Ce introduced by the rare earth orthosilicate scintillating material is only doped with silicon lattice sites. 4+ Still limited, the material still has extremely strong photoluminescent properties.

[0010] On this basis, the inventors found that for LYSO:Ce materials, by simultaneously introducing silicon lattice doping and rare earth doping and controlling the doping amount, without affecting the light yield and scintillation performance, on the one hand, the amount of Ce2 relative to Ce1 can be reduced, and at the same time, a large amount of stable Ce can be introduced. 4+ Under the synergistic effect of these two, a scintillation material with high light yield, ultrafast scintillation decay, and extremely low fluorescence performance can be obtained, and the present invention was completed on this basis.

[0011] According to a first aspect of the present invention, an ultrafast, high-brightness, and extremely low-fluorescence rare earth orthosilicate scintillating material is provided. The chemical formula of the ultrafast, high-brightness, and extremely low-fluorescence rare earth orthosilicate scintillating material is RE 2(1-x-y-a) Ce 2x Ca 2y A 2a Si (1-z) Al z O5; wherein, 0<x≤0.05, 0<y≤0.02, 0<z≤0.05, 0≤a≤0.01; the RE represents a rare earth element, and the rare earth element is selected from at least one of lanthanum, lutetium, yttrium, and gadolinium; the A represents other doping elements, and the other doping elements are selected from at least one of lithium Li, sodium Na, potassium K, rubidium Rb, cesium Cs, magnesium Mg, strontium Sr, scandium Sc, ytterbium Yb, and copper Cu.

[0012] Furthermore, the rare earth element is lutetium and / or yttrium.

[0013] Furthermore, the rare earth elements are lutetium and yttrium; wherein the molar ratio of lutetium:yttrium is (7-9):1.

[0014] In some embodiments, in the chemical formula of the ultrafast, high-brightness, and extremely low-fluorescence rare earth orthosilicate scintillating material, 0.0001≤x≤0.003, 0.001≤y<0.003, and 0.001≤z≤0.01.

[0015] In other embodiments, in the chemical formula of the ultrafast, high-brightness and extremely low-fluorescence rare earth orthosilicate scintillating material, 0.0001≤x≤0.003, 0.003≤y≤0.005, and 0.001≤z≤0.01.

[0016] Furthermore, the scintillation light output of the ultrafast, high-brightness and extremely low-fluorescence rare earth orthosilicate scintillation material is greater than 10 4 ph. / MeV, the scintillation light decay time is within 35ns, and the fluorescence response is within 5% of that of LYSO:Ce scintillating material. Furthermore, the absorption coefficient at 358nm in the optical absorption spectrum is <2.5cm -1 .

[0017] According to a second aspect of the present invention, a method for preparing an ultrafast, high-brightness, and extremely low-fluorescence rare earth orthosilicate scintillating material is provided. The chemical formula of the ultrafast, high-brightness, and extremely low-fluorescence rare earth orthosilicate scintillating material is RE 2(1-x-y-a) Ce 2x Ca 2y A 2a Si (1- z) Al zO5; wherein, 0<x≤0.05, 0<y≤0.02, 0<z≤0.05, 0≤a≤0.01; RE represents a rare earth element, and the rare earth element is selected from at least one of lanthanum, lutetium, yttrium, and gadolinium; A represents other doping elements, and the other doping elements are selected from at least one of lithium Li, sodium Na, potassium K, rubidium Rb, cesium Cs, magnesium Mg, strontium Sr, scandium Sc, ytterbium Yb, and copper Cu; The ultrafast, high-brightness, and extremely low-fluorescence rare earth orthosilicate scintillating material is a single crystal, and the preparation method comprises the following steps: S1, weighing rare earth oxides, CeO2, SiO2, Al2O3, oxides of other doping elements, CaCO3 or CaO as raw materials according to the chemical formula of the ultrafast, high-brightness, and extremely low-fluorescence rare earth orthosilicate scintillating material, and fully mixing them to obtain a mixed powder; S2, after pressing the mixed powder into a shape, solid-phase reaction is carried out at 1000-2000°C for 5-200 hours to obtain a polycrystalline material with a single phase composition; S3, the polycrystalline material is placed in a container and heated to melt it, and the melt is controlled to slowly cool and crystallize to obtain a single crystal crude product; S4, the single crystal crude product is annealed at 1000-1400°C for 10-200 hours to obtain the ultrafast, high-brightness and extremely low-fluorescence rare earth orthosilicate scintillating material.

[0018] Furthermore, the step S4 specifically includes: placing the single crystal crude product in a muffle furnace, and introducing air or a mixture of inert gas and oxygen into it; then, heating the muffle furnace to 1000-1400°C at a heating rate of less than 300°C / hour, and keeping it warm for 10-200 hours; thereafter, cooling to room temperature at a rate of less than 150°C / hour to obtain the ultrafast, high-brightness, and extremely low-fluorescence rare earth orthosilicate scintillating material.

[0019] According to the third aspect of the present invention, there is provided the application of the ultrafast, high-brightness, and extremely low-fluorescence rare earth orthosilicate scintillating material of any embodiment of the first aspect in any field including mixed-field radiation detection, high-energy physics detection and particle identification, and nuclear medicine imaging.

[0020] The above technical solution of the present invention has at least one of the following beneficial effects.

[0021] According to the ultrafast, high-brightness and extremely low-fluorescence rare earth orthosilicate scintillating material of the embodiment of the present invention, Ca is carried out in the rare earth orthosilicate scintillating material. 2+ With Al 3+ Simultaneous doping, Ca 2+ Due to its large ionic radius and strong electron-withdrawing properties, it mainly occupies the RE1 site. 3+ Because of Si 4+ The ionic radius is close and the Al-O bond is very similar to the Si-O bond, which mainly occupies the Si lattice site, that is, the rare earth lattice site and the silicon lattice site are doped at the same time. The two can form and This type of composite defect reduces the oxygen vacancy during the scintillation process The carrier capture ability of Ca 2+ and Al 3+ The double-site co-doping of Ce 3+ The emission peak is blue-shifted and broadened, the Ce1 content is greatly increased, the luminescence decay time is significantly shortened, and the scintillation light yield gain and afterglow performance are improved; and due to the simultaneous formation of point defects AlSi' and CaLu', a large amount of Ce 3+ Transformed into stable Ce 4+ To maintain charge balance, thus bypassing Ce 3+ The initial hole capture process of the emission further shortens the scintillation decay time; at the same time, due to the Ce 4+ Empty 4f ground state, the material has extremely low fluorescence response and is completely resistant to ultraviolet interference. That is to say, the ultrafast, high-brightness and extremely low-fluorescence rare earth orthosilicate scintillating material according to the embodiment of the present invention can simultaneously take into account high light yield, fast scintillation decay, and extremely low fluorescence response. Ca, Al co-doping can obtain the best quality factor at a low Ca doping concentration (0.1%), significantly reducing the Ca doping concentration, and avoiding the crystal distortion, off-axis growth and crushing cracking problems caused by the sharp drop in melt surface tension caused by Ca doping during crystal growth. Therefore, Ca, Al co-doping can greatly improve the crystal yield, facilitate the growth of large-size crystals and batch engineering preparation. Ca, Al co-doping has a greater acceleration of the decay time than Ca or Al single doping.

[0022] LYSO:Ce,Ca,Al can achieve the effect of improving the scintillation performance by co-doping with high concentration 0.4%Ca at a lower doping concentration. In some embodiments, the present invention can achieve a higher quality factor while lower (<0.3%) Ca 2+ and Al 3+ Co-doping significantly increases the light yield and accelerates the decay time (~35ns).

[0023] In other embodiments, higher (≥0.3%) Ca 2+ and Al 3+ Co-doping will reduce the light yield (>10 4 ph. / MeV), and the decay time is greatly accelerated (20-30ns range); as long as Ca 2+ and Al 3+ The co-doping showed extremely low fluorescence response.

[0024] The ultrafast, high-brightness and extremely low-fluorescence rare earth orthosilicate scintillating material of this application has a scintillation light output of >104 ph. / MeV, the scintillation light decay time is within 35ns, and the fluorescence response is within 5% of the LYSO:Ce scintillation material. In addition, the optical absorption spectrum at 358nm (Ce 3+ Absorption coefficient at absorption peak) <2.5cm -1 , which can greatly reduce the self-absorption of the crystal and increase the output of scintillation photons from the inside of the crystal (equivalent to a higher light yield), especially for large-sized crystals.

[0025] In addition, the ultrafast, high-brightness, and ultra-low fluorescence rare earth orthosilicate scintillating material according to the present application also significantly reduces the afterglow level and has no photoinduced afterglow. At the same time, its extremely low fluorescence response characteristics mean that it does not require light-proofing during use and transportation, and is completely resistant to ultraviolet interference in application scenarios, thereby improving the detection signal-to-noise ratio.

[0026] Ultrafast, high-brightness, and extremely low-fluorescence rare earth orthosilicate scintillating materials can be better applied in mixed-field radiation detection, high-energy physics detection and particle identification, and nuclear medicine imaging (TOF-PET, PET-CT, PET-MRI) because of their high light yield, fast scintillation decay, extremely low fluorescence response, and extremely low afterglow level without photoinduced afterglow. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 shows Lu 1.7994-2y Y 0.2 Ce 0.0006 Ca 2y Si (1-z) Al z X-ray diffraction pattern of O5 (y=z=0.001,0.003) single crystal; Figure 2 is Lu 1.7994-2y Y 0.2 Ce 0.0006 Ca 2y Si (1-z) Al z Multi-channel energy spectrum of O5 (y=z=0.001, 0.003, 0.005) single crystal; Figure 3 is Lu 1.7994-2y Y 0.2 Ce 0.0006 Ca 2y Si (1-z) Al z The scintillation decay time spectrum of O5 (y=z=0.001, 0.003, 0.005) single crystal; Figure 4 is Lu 1.7994-2y Y 0.2 Ce 0.0006 Ca 2y Si (1-z) Al z Photoluminescence spectrum of O5 (y=z=0.001,0.003) single crystal; Figure 5 is Lu 1.7994-2y Y0.2 Ce 0.0006 Ca 2y Si (1-z) Al z Figure 6 is the optical absorption spectrum of Lu 1.7994-2y Y 0.2 Ce 0.0006 Ca 2y Si (1-z) Al z Figure 7 is the afterglow decay spectrum of O5 (y=z=0.001) single crystal; 1.7994-2y Y 0.2 Ce 0.0006 Ca 2y Si (1-z) Al z Figure 8 is a multi-channel energy spectrum of the Ca and Al co-doped LYSO:Ce crystals with different doping concentrations grown by the Czochralski method in Example 3; Figure 9 is a scintillation decay time spectrum of the Ca and Al co-doped LYSO:Ce crystals with different doping concentrations grown by the Czochralski method in Example 3; Figure 10 is a photograph of the Ca and Al co-doped LYSO:Ce crystals with different doping concentrations grown by the Czochralski method in Example 3 (the right is a photograph of the high concentration 0.4% Ca co-doped crystal); Figure 11 is a multi-channel energy spectrum of the Yb co-doped LYSO:Ce, Ca, Al, and Li crystals with different concentrations in Example 12 (LYSO:Ce, Ca, Al is used as a control group); Figure 12 is a scintillation decay time spectrum of the Yb co-doped LYSO:Ce, Ca, Al, and Li crystals with different concentrations in Example 12 (LYSO:Ce, Ca, Al is used as a control group); Table 1 in Figure 13 shows the fluorescence and scintillation properties of each crystal sample in Example 5; Table 2 in Figure 14 shows the scintillation performance of LYSO:Ce crystals co-doped with Ca and Al at different concentrations in Example 3; Table 3 in Figure 15 shows the scintillation performance of LYSO:Ce, Ca, Al crystals doped with Li at different concentrations in Example 9; Table 4 in Figure 16 shows the scintillation performance of LYSO:Ce, Ca, Al, Li / Mg / Cu crystals doped with Yb at different concentrations in Example 12, Example 14, and Example 16; Table 5 in Figure 17 shows the scintillation performance of LYSO:Ce, Ca, Al crystals doped with Mg at different concentrations in Example 13; Table 6 in Figure 18 shows the scintillation performance of LYSO:Ce, Ca, Al crystals doped with Cu at different concentrations in Example 15. DETAILED DESCRIPTION

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field are within the scope of protection of the present invention.

[0029] The following first describes the ultrafast, high-brightness, and extremely low-fluorescence rare earth orthosilicate scintillating material according to an embodiment of the present application.

[0030] The ultrafast, high-brightness, and extremely low-fluorescence rare earth orthosilicate scintillating material according to the embodiment of the present application has the chemical formula RE 2(1-x-y- a) Ce 2x Ca 2y A 2a Si (1-z) Al z O5; wherein, 0<x≤0.05, 0<y≤0.02, 0<z≤0.05, and 0≤a≤0.01. The RE represents a rare earth element, and the rare earth element is selected from at least one of lanthanum, lutetium, yttrium, and gadolinium. Alternatively, the chemical formula of the ultrafast, high-brightness, and extremely low-fluorescence rare earth orthosilicate scintillating material can be simplified to RESO:xCe,yCa,zAl,aA. The A represents other doping elements, and the other doping elements are selected from at least one of lithium Li, sodium Na, potassium K, rubidium Rb, cesium Cs, magnesium Mg, strontium Sr, scandium Sc, ytterbium Yb, and copper Cu.

[0031] In the present invention, Ca / Ce co-doping can bring a large amount of stable Ce compared to co-doping of one of lithium Li, sodium Na, potassium K, rubidium Rb, cesium Cs, magnesium Mg, strontium Sr, scandium Sc, ytterbium Yb, copper Cu and Ce. 4+ . Moreover, Ca / Ce co-doped scintillating materials have extremely low fluorescence properties. Among them, if the y value and the z value are excessive, it will cause the single crystal to be difficult to prepare due to the high impurity content, and at the same time cause the scintillation light output to deteriorate significantly. If the A element is excessive, it will lead to an increase in electronic defects and a significant deterioration in the scintillation light output. In other words, the present invention provides a method for reducing the fluorescence response of rare earth orthosilicate scintillating materials, comprising: in the rare earth orthosilicate scintillating material RE 2(1-x-a) Ce 2x Si (1-z) Al z A 2aA specific amount of Ca is introduced into the RE position of O5 (the ratio of Ca to the total rare earth sites is 2y / 2, where 0 < y ≤ 0.02) to enhance the scintillation performance of the rare earth orthosilicate scintillating material while reducing the fluorescence response. RE represents a rare earth element selected from at least one of lanthanum, lutetium, yttrium, and gadolinium. A represents another doping element selected from at least one of lithium Li, sodium Na, potassium K, rubidium Rb, cesium Cs, magnesium Mg, strontium Sr, scandium Sc, ytterbium Yb, and copper Cu.

[0032] According to the ultrafast, high-brightness and extremely low-fluorescence rare earth orthosilicate scintillating material of the embodiment of the present invention, Ca is carried out in the rare earth orthosilicate scintillating material. 2+ With Al 3+ Simultaneous doping, Ca 2+ Due to its large ionic radius and strong electron-withdrawing properties, it mainly occupies the RE1 site. 3+ Because of Si 4+ The ionic radius is close and the Al-O bond is very similar to the Si-O bond, mainly occupying the Si lattice site.

[0033] In addition, Figure 1 shows that Ca 2+ With Al 3+ The X-ray diffraction patterns of the LYSO:Ce material (i.e., undoped Ca) are shown as reference. 2+ With Al 3+ ), and doped with Al only 3+ And its doping amount is 0.6% (equivalent to the atomic percentage of Si) X-ray diffraction spectrum. As shown in Figure 1, all the diffraction peaks recorded in the figure can be obtained by (Lu 1.81 Y 0.19 )SiO5 structure index (PDF#97-015-9308), and there is no impurity peak. In addition, compared with LYSO:Ce material, Al 3+ The doped X-ray diffraction peak shifts to a lower angle, indicating that doping increases the unit cell volume. 3+ Radius 56pm, rare earth RE 3+ Ionic radius > 100 pm, Si 4+ Radius 40pm, if Al 3+ Replace rare earth RE 3+ The lattice position will inevitably lead to a decrease in the unit cell volume, that is, the increase in the unit cell volume indicates that the Al 3+ Occupies the Si lattice site. Moreover, the diffraction peak shifts further to a smaller angle after Ca and Al co-doping. This is related to the larger radius of Al 3+ , Ca 2+ Replace Lu respectively 3+ 、Si 4+, and their synergistic effect further increases the unit cell volume.

[0034] That is, according to the ultrafast, high-brightness and extremely low-fluorescence rare earth orthosilicate scintillating material of the present application, Ca 2+ With Al 3+ Simultaneous doping of rare earth sites and silicon sites is achieved, and the two can form and This type of composite defect reduces the oxygen vacancy during the scintillation process carrier capture capability, thereby optimizing the scintillation light output and afterglow performance.

[0035] In addition, Figure 2 shows the multi-channel energy spectra of LYSO:Ce, LYSO:Ce, 0.1at%Ca, 0.1at%Al and LYSO:Ce, 0.3at%Ca, 0.3at%Al single crystals. As shown in Figure 2, when a small amount of Ca is doped 2+ With Al 3+ In the case of LYSO:Ce, 0.1at%Ca, 0.1at%Al, the light yield can be further improved compared with LYSO:Ce.

[0036] Figure 3 shows the scintillation decay time spectra of LYSO:Ce, LYSO:Ce, 0.1at%Ca, 0.1at%Al, LYSO:Ce, 0.3at%Ca, 0.3at%Al and LYSO:Ce, 0.5at%Ca, 0.5at%Al single crystals. The fitted decay times are 40.6ns, 34.5ns, 31.6ns and 28.7ns, respectively. As shown in Figure 3, the decay time is further improved with the increase of doping amount. Combining Figures 2 and 3, it can be seen that the lower (<0.3%) Ca 2+ and Al 3+ Co-doping can significantly increase the light yield and accelerate the decay time (~35ns). 2+ and Al 3+ Co-doping will reduce the light yield (>10 4 ph. / MeV), while the decay time is greatly accelerated (approaching 30ns)

[0037] Figure 4 shows the photoluminescence spectra of LYSO:Ce, LYSO:Ce, 0.1at%Ca, 0.1at%Al and LYSO:Ce, 0.3at%Ca, 0.3at%Al single crystals. As can be seen from the figure, according to the ultrafast high-brightness and extremely low-fluorescence rare earth orthosilicate scintillating material of the present application, Ca 2+ With Al 3+When doped with LYSO:Ce, 0.1at% Ca, 0.1at% Al and LYSO:Ce, 0.3at% Ca at the same time, the relative fluorescence intensity (i.e., the fluorescence intensity relative to LYSO:Ce) of the single crystals is less than 5%. That is to say, the ultrafast, high-brightness and extremely low-fluorescence rare earth orthosilicate scintillating material of the present application achieves an extremely low fluorescence response, solving the problem of photo-afterglow caused by ambient ultraviolet rays.

[0038] Figure 5 shows the optical absorption spectra of LYSO:Ce, LYSO:Ce, 0.6at%Al, LYSO:Ce, 0.1at%Ca, 0.1at%Al and LYSO:Ce, 0.3at%Ca, 0.3at%Al single crystals. 3+ The optical absorption spectrum of LYSO:Ce,0.6at%Al crystal after doping obviously shows Ce 4+ -O 2- Charge transfer band (CT), attributed to the Al 3+ Replace Si 4+ Then a negatively charged point defect Al′ is formed Si , under the action of charge balance, Al′ Si Induced part Ce 3+ Transformed into stable Ce 4+ In addition, it can be seen from the figure that the LYSO:Ce, 0.1at%Ca, 0.1at%Al and LYSO:Ce, 0.3at%Ca, 0.3at%Al single crystals according to the two embodiments of the present application not only have obvious Ce 4+ -O 2- Charge transfer band (CT), and Ce 3+ The absorption coefficient of the absorption peak (358nm) is less than 2.5cm -1 , and the corresponding Ce 4+ The absorption peak is significantly enhanced. 3+ absorption peak) absorption coefficient significantly reduced (<2.5cm -1 ), which can greatly reduce the self-absorption of the crystal, and the gain scintillation photons are output from the inside of the crystal (equivalent to a higher light yield), especially for large-sized crystals. In addition, due to the point defect Al Si ' and Ca Lu ' is formed at the same time, resulting in a large amount of Ce 3+ Transformed into stable Ce 4+ To maintain charge balance, thus bypassing Ce 3+ The initial hole capture process of the emission further shortens the scintillation decay time; at the same time, due to the Ce 4+ The material has an empty 4f ground state and has extremely low fluorescence response and is completely resistant to ultraviolet interference.

[0039] Figure 6 shows the afterglow decay spectra of LYSO:Ce, LYSO:Ce, 0.3at%Ca, LYSO:Ce, 0.6at%Al and LYSO:Ce, 0.1at%Ca, 0.1at%Al single crystals, and Figure 7 shows the X-ray excitation spectra of LYSO:Ce, LYSO:Ce, 0.6%Al, LYSO:Ce, 0.3%Ca, LYSO:Ce, 0.1at%Ca, 0.1at%Al and LYSO:Ce, 0.3at%Ca, 0.3at%Al single crystals. As shown in Figure 6, the afterglow performance of LYSO:Ce co-doped with Ca and Al is significantly improved compared with LYSO:Ce doped with Ca or Al alone. As shown in Figure 7, the afterglow performance of Ca co-doped with Ca and Al is significantly improved compared with LYSO:Ce doped with Ca or Al alone. 2+ and Al 3+ The double-site co-doping of Ce 3+ The emission peak is blue-shifted and its broadening is narrowed, and the Ce1 content is greatly increased, thereby significantly shortening the luminescence decay time, and obtaining an improvement in the scintillation light yield gain and afterglow performance.

[0040] In summary, the ultrafast, high-brightness, and extremely low-fluorescence rare earth orthosilicate scintillating material according to the embodiment of the present invention can simultaneously take into account high light yield, fast scintillation decay, and extremely low fluorescence response, and also significantly reduce the afterglow level without photoinduced afterglow. At the same time, the extremely low fluorescence response characteristic makes it unnecessary to avoid light during use and transportation, and is completely resistant to ultraviolet interference in application scenarios, and the detection signal-to-noise ratio is improved. According to the ultrafast, high-brightness, and extremely low-fluorescence rare earth orthosilicate scintillating material of the present application, because it takes into account high light yield, fast scintillation decay, extremely low fluorescence response, and extremely low afterglow level without photoinduced afterglow, it can be better applied to the fields of mixed field radiation detection, high-energy physics detection and particle identification, and nuclear medicine imaging (TOF-PET, PET-CT, PET-MRI).

[0041] In addition, the ultrafast, high-brightness, and extremely low-fluorescence rare earth orthosilicate scintillating material of the present application can be doped or not doped with other doping elements. In other words, when a is 0, that is, it is not doped with the other doping elements mentioned, and its chemical formula is RE 2(1-x- y) Ce 2x Ca 2y Si (1-z) Al z O5, when a is greater than 0, it is doped with other doping elements mentioned above. Whether to dope such elements or not can be appropriately selected according to the actual use scenario, performance requirements, etc. + 、Na + etc. tend to occupy the six-coordinate interstitial space or rare earth position, inhibiting The formation or spatial correlation of Ce and The dissociation of Cu can improve the scintillation light yield, have a negative impact on reducing the fluorescence intensity, and have no obvious effect on accelerating the scintillation decay time; 2+ Mg 2+ The combined effect of enhanced thermal ionization of the 5d1 state of cerium ions and reduced emission contribution of Ce2 centers (i.e., sites adjacent to six oxygens) will further shorten the decay time, but will have no significant effect on reducing the fluorescence intensity and slightly worsen the light yield. 3+ It can act as a competitive luminescence center, causing Ce-Yb energy transfer, which greatly shortens the decay time. At the same time, Yb tends to form Yb 2+ ions, promoting more Ce through charge balance 3+ Transformed into Ce 4+ , so that the fluorescence intensity is further reduced. Those skilled in the art can appropriately choose to add or not add corresponding other doping elements based on specific usage scenarios and performance requirements.

[0042] Furthermore, the rare earth elements are preferably lutetium and / or yttrium, more preferably lutetium and yttrium, wherein the molar ratio of lutetium:yttrium is (7-9):1. By introducing Y, which is cheaper, has a lower melting point, and a larger ionic radius, into LSO:Ce crystals, and combining it with lutetium (Lu) at the aforementioned molar ratio to prepare a solid solution LYSO:Ce, this can lower the melting point, reduce costs (raw materials and electricity costs for single crystal growth), reduce defect levels, and optimize crystal performance.

[0043] The ultrafast, high-brightness, and extremely low-fluorescence rare earth orthosilicate scintillating material and its preparation method of the present application are further described below with reference to specific examples.

[0044] Example 1 (Growth of Y by Czochralski Method) 2(1-x-y) Ce 2x Ca 2y Si (1-z) Al zO5 single crystals were grown using the Czochralski method. The molar ratio of Y2O3:CeO2:CaCO3:SiO2:Al2O3 was 1-xy:2x:2y:1-z: z / 2 (x = 0.0001, 0.0003, 0.001, 0.003, 0.006, 0.01, 0.03, 0.05; y = 0.0005, 0.001, 0.002, 0.004, 0.008, 0.01, 0.02; z = 0.0005, 0.001, 0.002, 0.004, 0.008, 0.01, 0.02, 0.04, 0.05). After thorough mixing, the mixture was cold isostatically pressed at 250 MPa. The pressed block is placed in an iridium crucible, and in a nitrogen atmosphere, it is fully melted by induction heating. After seeding, a single crystal of a preset size is slowly pulled out from the melt to obtain Y 2(1-x-y) Ce 2x Ca 2y Si (1-z) Al z O5 single crystal. The parameters of the Czochralski pulling method include: a pulling speed of 0.7 to 3 mm / h and a rotation speed of 3 to 15 r / min.

[0045] Example 2 (Growth of Y by Czochralski Method) 1.99 Ce 0.002 Ca 0.002 Si (1-z) Al z Y2O3 single crystal) is grown by the Czochralski method. The molar ratio of Y2O3:CeO2:CaCO3:SiO2:Al2O3=0.998:0.002:0.002: 1-z:z / 2 (where z=0.0005, 0.001, 0.002, 0.004, 0.008, 0.01, 0.02, 0.04, 0.05) is used for mixing. After fully mixing, the mixture is pressed by cold isostatic pressing (pressure of 250MPa). The pressed block is placed in an iridium crucible, with nitrogen as the protective atmosphere, and is fully melted by induction heating. After seeding, a single crystal of a preset size is slowly pulled out from the melt to obtain Y2O3. 1.99 Ce 0.002 Ca 0.002 Si (1-z) Al z O5 single crystal. The parameters of the Czochralski method include: pulling speed of 2-4 mm / h and rotation speed of 10-20 r / min.

[0046] Example 3 (Czochralski growth of Lu 2(1-x-y) Ce 2x Ca 2y Si (1-z) Al zO5 single crystals were grown using the Czochralski method. The molar ratio of Lu2O3:CeO2:CaCO3:SiO2:Al2O3 was 1-xy:2x:2y:1-z: z / 2 (x = 0.0001, 0.0003, 0.001, 0.003, 0.006, 0.01, 0.03, 0.05; y = 0.0005, 0.001, 0.002, 0.004, 0.008, 0.01, 0.02; z = 0.0005, 0.001, 0.002, 0.004, 0.008, 0.01, 0.02, 0.04, 0.05). After thorough mixing, the mixture was cold isostatically pressed at 250 MPa. The pressed block is placed in an iridium crucible, and in a nitrogen atmosphere, it is fully melted by induction heating. After seeding, a single crystal of a preset size is slowly pulled out from the melt to obtain Lu 2(1-x-y) Ce 2x Ca 2y Si (1-z) Al z The parameters of the Czochralski pulling method include: design of required dimensional parameters, temperature field design, PID quality control temperature, pulling speed of 1-5 mm / h, and rotation speed of 8-10 r / min.

[0047] Figure 8 shows the multi-channel energy spectra of LYSO:Ce, 0.1 at.% Ca, 0.2 at.% Al, LYSO:Ce, 0.2 at.% Ca, 0.4 at.% Al, and LYSO:Ce, 0.3 at.% Ca, 0.6 at.% Al single crystals. Figure 8 shows that after optimizing the Ca and Al co-doping ratios, even at relatively low doping concentrations (i.e., y ≤ 0.003, z ≤ 0.006), light yields exceeding 30,000 ph / MeV can be achieved.

[0048] Figure 9 shows the scintillation decay time spectra for LYSO:Ce, 0.1 at.% Ca, 0.2 at.% Al, LYSO:Ce, 0.2 at.% Ca, 0.4 at.% Al, and LYSO:Ce, 0.3 at.% Ca, 0.6 at.% Al single crystals. The fitted decay times are 33.9 ns, 32.6 ns, and 30.3 ns, respectively. As shown in Figure 9, the decay time further improves with increasing doping levels.

[0049] Figure 10 shows crystal photographs of LYSO:Ce, 0.1 at.% Ca, 0.2 at.% Al, LYSO:Ce, 0.2 at.% Ca, 0.4 at.% Al, and LYSO:Ce, 0.3 at.% Ca, 0.6 at.% Al. Combined with the crystal photographs of LSO:Ce with a high concentration (>0.4 at.% Ca) and the scintillation performance parameters in Table 2, it can be seen that the scintillation performance enhancement effect of LYSO:Ce, Ca, and Al can be achieved at a lower doping concentration compared to a high concentration of 0.4% Ca. This method achieves a higher quality factor while significantly reducing the Ca doping concentration, avoiding the problems of crystal distortion, off-axis growth, and comminutive cracking caused by the sharp drop in melt surface tension during crystal growth. This significantly improves the crystal yield and facilitates the growth of large-scale crystals and batch engineering production.

[0050] Table 2 shows the scintillation performance of Ca and Al co-doped LYSO:Ce crystals with different doping concentrations in Example 3.

[0051] Table 2 shows that Ca, Al co-doped LYSO:Ce prepared by the Czochralski method achieves decay times <35ns and light yields >30,000 ph / MeV at certain doping concentrations (i.e., y ≤ 0.003, z ≤ 0.006). Ca, Al co-doping achieves the best quality factor at low Ca doping concentrations (0.1%). Ca, Al co-doping significantly accelerates decay time compared to Ca or Al doping alone.

[0052] Example 4 (Micro-pull-down method to grow Lu 1.8-2x-2y Y 0.2 Ce 2x Ca 2y Si (1-z) Al z O5) Single crystals were grown using the micro-pull-down method (μ-PD). The molar ratio is Lu2O3:Y2O3:CeO2:CaCO3:SiO2:Al2O3. =0.9-xy:0.1:2x:2y:1-z:z / 2 ingredients (wherein x=0.0001, 0.0003, 0.001, 0.003, 0.006, 0.01, 0.03, 0.05; y=0.0005, 0.001, 0.002, 0.004, 0.008, 0.01, 0.02; z=0.0005, 0.001, 0.002, 0.004, 0.008, 0.01, 0.02, 0.04, 0.05), after fully mixing, use a muffle furnace to pre-sinter the mixed powder at 1600 ° C for 20 hours, put the sintered polycrystalline material into an iridium crucible, use nitrogen as a protective atmosphere, and fully melt it by induction heating. After the seed crystal contacts the melt, it is slowly pulled down to obtain Lu 1.8-2x-2y Y 0.2 Ce2x Ca 2y Si (1-z) Al z O5 single crystal. Parameters of the micro-pull-down method include: a micro-pull-down speed of 3 to 20 mm / h.

[0053] Example 5 (Micro-pull-down method to grow Lu 1.7994-2y Y 0.2 Ce 0.0006 Ca 2y Si (1-z) Al z O5 single crystal) is grown using the micro-pull-down method (μ-PD). The molar ratio is Lu2O3:Y2O3:CeO2:CaCO3:SiO2:Al2O3 =0.8997-y:0.1:0.0006:2y:1-z:z / 2 ingredients (wherein y=0, 0.0005, 0.001, 0.002, 0.003, 0.004, 0.005, 0.008, 0.01, 0.02; z=0, 0.0005, 0.001, 0.002, 0.003, 0.004, 0.005, 0.008, 0.01, 0.02, 0.04, 0.05), after fully mixing, use a muffle furnace to pre-sinter the mixed powder at 1600 ° C for 20 hours, put the sintered polycrystalline material into an iridium crucible, use nitrogen as a protective atmosphere, and fully melt it by induction heating. After the seed crystal contacts the melt, it is slowly pulled down to obtain Lu 1.7994-2y Y 0.2 Ce 0.0006 Ca 2y Si (1-z) Al z O5 single crystal, wherein the parameters of the micro-pull-down method include: required size parameter design, temperature field design, and micro-pull-down speed of 10-15 mm / h.

[0054] Among them, the crystal sample Lu 1.7994-2y Y 0.2 Ce 0.0006 Ca 2y Si (1-z) Al z O5 (y=z=0.0005, 0.001, 0.003, 0.005) are marked as LYSO:Ce, 0.05at%Ca, 0.05at%Al (the actual composition is Lu 1.7984 Y 0.2 Ce 0.0006 Ca 0.001 Si 0.9995 Al 0.0005 O5), LYSO: Ce, 0.1at% Ca, 0.1at% Al (the actual composition is Lu 1.7974 Y0.2 Ce 0.0006 Ca 0.002 Si 0.999 Al 0.001 O5), LYSO: Ce, 0.3at% Ca, 0.3at% Al (the actual composition is Lu 1.7934 Y 0.2 Ce 0.0006 Ca 0.006 Si 0.997 Al 0.003 O5) and LYSO:Ce, 0.5at%Ca, 0.5at%Al (the actual composition is Lu 1.7894 Y 0.2 Ce 0.0006 Ca 0.01 Si 0.997 Al 0.005 O5).

[0055] In order to compare the unique beneficial effects of Ca and Al co-doping, undoped (Lu 1.7994 Y 0.2 Ce 0.0006 SiO5), single doped with 0.3% Ca (Lu 1.7934 Y 0.2 Ce 0.0006 Ca 0.006 SiO5), single doped with 0.3% Al (Lu 1.7994 Y 0.2 Ce 0.0006 Si 0.997 Al 0.003 O5) and single doped 0.6% Al(Lu 1.7994 Y 0.2 Ce 0.0006 Si 0.994 Al 0.006 O5) single crystals, marked as LYSO:Ce, LYSO:Ce, 0.3%Ca, LYSO:Ce, 0.3%Al, and LYSO:Ce, 0.6%Al, respectively.

[0056] The Ce1 / Ce2 fitting relative content, relative fluorescence intensity, scintillation decay time, and relative light yield of each crystal sample in Example 5 are shown in Table 1. For comparison, the properties of non-co-doped LYSO:Ce and Ca or Al-doped LYSO:Ce single crystals are also shown.

[0057] Among them, three Gaussian peaks (peak positions are: 3.13, 2.95 and 2.69 eV) are used to fit the XEL spectrum, and the Ce1 / Ce2 ratio can be obtained by calculating the ratio of the Gaussian peak areas of Ce1 and Ce2.

[0058] Fluorescence spectra were measured using a fluorescence spectrometer using a 450W continuous xenon lamp as the excitation source. Relative fluorescence intensity is the percentage ratio of the strongest peak in the fluorescence spectrum of the sample to that of LYSO:Ce.

[0059] The optical absorption spectrum from 200 to 800 nm was obtained using an ultraviolet-infrared photometer, and the absorption coefficient at 358 nm was read.

[0060] The flicker decays to 137 Under Cs irradiation, the scintillation decay curve was recorded using a photomultiplier tube (Hamamatsu R6233 PMT) and an oscilloscope (Agilent DSO 9404A). A single exponential fitting was performed to obtain the decay time of the pulse spectrum; the decay time was recorded by a PMT and a channel analyzer. 137 The pulse height spectrum of the sample under 662keV gamma radiation from a Cs radiation source. The channel number is read from the pulse height spectrum and compared to the absolute light yield of a standard LYSO:Ce sample calibrated using single photons to obtain the relative light yield.

[0061] Table 1 shows the fluorescence and scintillation properties of the crystal samples in Example 5 (where the subscript Ce is 0.006). It should be noted that the preparation processes of LYSO:Ce, 0.1 at% Li, 0.5 at% Al, LYSO:Ce, 0.3 at% Cu, 0.5 at% Al, and LYSO:Ce, 0.3 at% Mg, 0.5 at% Al in Table 1 refer to those of LYSO:Ce, 0.5 at% Ca, 0.5 at% Al.

[0062] Combined with Table 1, it can be seen that compared with non-co-doped LYSO:Ce and Ca or Al single-doped LYSO:Ce, Ca, Al co-doped LYSO:Ce has a significantly increased fast luminescence Ce1 ratio, extremely low fluorescence response (<5%), and extremely low Ce 3+ The optical absorption spectrum intensity is significantly accelerated while the scintillation decay is maintained at 10 4 High light output above ph. / MeV.

[0063] Example 6 (Growth of Gd by Czochralski Method) 1.998-2y Ce 0.002 Ca 2y Si 0.994 Al 0.006O5) Single crystals are grown using the Czochralski method. The molar ratio of Gd2O3:CeO2:CaCO3:SiO2:Al2O3=0.999-y:0.002:2y: 0.994:0.003 (where y=0.0005, 0.001, 0.0015, 0.002, 0.003, 0.004, 0.008, 0.01, 0.02) is used for mixing. After fully mixing, the mixture is pressed by cold isostatic pressing (pressure of 250MPa). The pressed block is placed in an iridium crucible, protected by nitrogen, and fully melted by induction heating. After seeding, a single crystal of a preset size is slowly pulled out from the melt to obtain Gd 1.998-2y Ce 0.002 Ca 2y Si 0.994 Al 0.006 O5 single crystal. The parameters of the Czochralski pulling method include: a pulling speed of 0.7 to 6 mm / h and a rotation speed of 6 to 20 r / min.

[0064] Example 7 (Micro-pull-down method to grow Lu 1.6 Y 0.2 Gd 0.2 Ce 2x Ca 2y Si 1-z Al z O5) Single crystals were grown using the micro-pull-down method (μ-PD). The molar ratio of Lu2O3:Y2O3:Gd2O3:CeO2:CaCO3:SiO2: Al2O3 is 0.8:0.1:0.1:2x:2y:1-z:z / 2 (where x = 0.0001, 0.0003, 0.001, 0.003, 0.006, 0.01, 0.03, 0.05; y = 0.0005, 0.001, 0.0015, 0.002, 0.004, 0.005, 0.006, 0.0 08, 0.01, 0.02; z = 0.0005, 0.001, 0.002, 0.004, 0.008, 0.01, 0.02, 0.04, 0.05), after fully mixing, use a muffle furnace to pre-sinter the mixed powder at 1600 ° C for 30 hours, put the sintered polycrystalline material into an iridium crucible, use nitrogen as a protective atmosphere, and fully melt it by induction heating. After the seed crystal contacts the melt, it is slowly pulled down to obtain Lu 1.6 Y 0.2 Gd 0.2 Ce 2x Ca 2y Si 1-z Al z O5 single crystal. Parameters of the micro-pull-down method include: a micro-pull-down speed of 10 to 20 mm / h.

[0065] Example 8 (Micro-pull-down method to grow Lu 1.9-2x-2y La 0.1 Ce 2x Ca 2y Si 1-z Al z O5) Single crystals were grown using the micro-pull-down method (μ-PD). The molar ratio of Lu2O3:La2O3:CeO2:CaCO3:SiO2:Al2O3 was 0.95-xy:0.05:2x:2y:1-z:z / 2 (where x=0.0001, 0.0003, 0.001, 0.003, 0.006, 0.01, 0.03, 0.05; y=0.0005, 0.001, 0.0015, 0.002, 0.003, 0.005, 0.006, 0.008, 0. 01, 0.02; z = 0.0005, 0.001, 0.002, 0.003, 0.004, 0.008, 0.01, 0.02, 0.04, 0.05), after fully mixing, use a muffle furnace to pre-sinter the mixed powder at 1600 ° C for 20 hours, put the sintered polycrystalline material into an iridium crucible, use nitrogen as a protective atmosphere, and fully melt it by induction heating. After the seed crystal contacts the melt, it is slowly pulled down to obtain Lu 1.9-2x-2y La 0.1 Ce 2x Ca 2y Si 1-z Al z The parameters of the micro-pull-down method include a micro-pull-down speed of 5 to 20 mm / h.

[0066] Example 9 (Growth of Lu1.798-2y-2aY by Czochralski method) 0.2 Ce 0.002 Ca 2y Li 2a Si (1-z) Al zSingle crystals were grown using the Czochralski method. The molar ratio of Lu₂O₃:Y₂O₃:CeO₂:CaCO₃:Li₂CO₃:SiO₂:Al₂O₃ was 0.899, with ya:0.1:0.002:2y:a:1-z:z / 2 (y = 0.0005, 0.001, 0.0015, 0.002, 0.004, 0.008, 0.01, 0.02; a = 0.0005, 0.001, 0.003; z = 0.0005, 0.001, 0.002, 0.004, 0.008, 0.01, 0.02, 0.04, 0.05). After thorough mixing, the mixture was cold isostatically pressed at 250 MPa. The pressed block was placed in an iridium crucible, and fully melted by induction heating in a nitrogen atmosphere. After seeding, a single crystal of a preset size was slowly pulled out from the melt to obtain Lu1.798-2y-2aY 0.2 Ce 0.002 Ca 2y Li 2a Si (1- z) Al z O5 single crystal. The parameters of the Czochralski method include: pulling speed of 1 to 5 mm / h and rotation speed of 3 to 10 r / min.

[0067] Table 3 shows the scintillation performance of LYSO:Ce,Ca,Al crystals with different Li doping concentrations in Example 9.

[0068] Example 10 (Growth of Lu1.798-2y-2aGd by Czochralski Method) 0.2 Ce 0.002 Ca 2y Cu 2a Si (1-z) Al zO5) Single crystals are grown using the Czochralski method. The ingredients are prepared in a molar ratio of Lu2O3:Gd2O3:CeO2:CaCO3:CuO:SiO2:Al2O3=0.899-ya:0.1:0.002:2y:2a:1-z:z / 2 (y=0.0005, 0.001, 0.0015, 0.002, 0.004, 0.008, 0.01, 0.02; a=0.001, 0.003, 0.005, 0.006, 0.008, 0.01; z=0.0005, 0.001, 0.002, 0.004, 0.008, 0.01, 0.02, 0.04, 0.05), and after being fully mixed, the mixture is pressed by cold isostatic pressing (pressure of 250 MPa). The pressed block is placed in an iridium crucible, and in a nitrogen atmosphere, it is fully melted by induction heating. After seeding, a single crystal of a preset size is slowly pulled out from the melt to obtain Lu 1.798-2y- 2a Gd 0.2 Ce 0.002 Ca 2y Cu 2a Si (1-z) Al z O5 single crystal. The parameters of the Czochralski method include: pulling speed of 3-10 mm / h and rotation speed of 2-10 r / min.

[0069] Example 11 (Growth of Lu1.598-2y-2aY by Czochralski method) 0.2 La 0.2 Ce 0.002 Ca 2y Sc 2a Si (1-z) Al z O5) Single crystals are grown using the Czochralski method. The molar ratio is Lu2O3:Y2O3:La2O3:CeO2:CaCO3:Sc2O3:SiO2:Al2O3 =0.799-ya:0.1:0.1:0.002:2y:a:1-z:z / 2(y=0.0005、0.001、0.0015、0.002、0.004、0.008、0.01、0.02;a=0.001、0.003、0.005、0.006、0.008、0.01;z=0.0005、0.001、0.002、0.004、0.008、0.01、0.02、0.04、0.05)are prepared, and after being fully mixed, the mixture is pressed by cold isostatic pressing (pressure is 250MPa). The pressed block is placed in an iridium crucible, and in a nitrogen atmosphere, it is fully melted by induction heating. After seeding, a single crystal of a preset size is slowly pulled out from the melt to obtain Lu1.598-2y- 2a Y 0.2 La 0.2 Ce 0.002 Ca 2y Sc 2a Si (1-z) Al z O5 single crystal. The parameters of the Czochralski method include: pulling speed of 4-10 mm / h and rotation speed of 5-12 r / min.

[0070] Example 12 (Czochralski growth of Lu 1.789-2a Y 0.2 Ce 0.002 Ca 0.003 Li 0.006 Yb 2a Si 0.998 Al 0.002 O5) Single crystals are grown using the Czochralski method. The molar ratio of Lu2O3:Y2O3:CeO2:CaCO3:Li2CO3:Yb2O3:SiO2:Al2O3 is 0.8945-a:0.1:0.002:0.003:0.003:a:0.998:0.001 (a=0.0001, 0.0003, 0.0005, 0.001). After thorough mixing, the mixture is pressed by cold isostatic pressing (pressure of 250MPa). The pressed block is placed in an iridium crucible, protected by nitrogen, and fully melted by induction heating. After seeding with a seed crystal, a single crystal of a preset size is slowly pulled out from the melt to obtain Lu 1.789- 2a Y 0.2 Ce 0.002 Ca 0.003 Li 0.006 Yb 2a Si 0.998 Al 0.002 O5 single crystal. The parameters of the Czochralski method include: pulling speed of 1 to 5 mm / h and rotation speed of 3 to 10 r / min.

[0071] Figure 11 shows the multi-channel energy spectra of LYSO:Ce, 0.15at.%Ca, 0.2at.%Al, LYSO:Ce, 0.15at.%Ca, 0.2at.%Al, 0.3%Li, 0.01at.%Yb, LYSO:Ce, 0.15at.%Ca, 0.2at.%Al, 0.3%Li, 0.03at.%Yb, and LYSO:Ce, 0.15at.%Ca, 0.2at.%Al, 0.3%Li, 0.05at.%Yb single crystals. As shown in Figure 11, the light yield of LYSO:Ce,Ca,Al crystals decreases with increasing Yb doping concentration, but the light yield is always >104 ph. / MeV.

[0072] Figure 12 shows the scintillation decay time spectra for LYSO:Ce, 0.15 at.% Ca, 0.2 at.% Al, LYSO:Ce, 0.15 at.% Ca, 0.2 at.% Al, 0.3% Li, 0.01 at.% Yb, LYSO:Ce, 0.15 at.% Ca, 0.2 at.% Al, 0.3% Li, 0.03 at.% Yb, and LYSO:Ce, 0.15 at.% Ca, 0.2 at.% Al, 0.3% Li, 0.05 at.% Yb single crystals. The fitted decay times are 33.8 ns, 28.8 ns, 25.0 ns, and 17.7 ns, respectively. Figure 12 shows that the decay time decreases sharply with increasing Yb doping levels. Combined with Table 4, it can be seen that Yb doping LYSO:Ce,Ca,Al,Li can further reduce its relative fluorescence intensity, accelerate the decay time to 30ns or even below 20ns, and maintain the light output at 10 4 ph. / MeV or above.

[0073] Table 4 shows the scintillation performance of LYSO:Ce,Ca,Al,Li / Mg / Cu crystals with different Yb doping concentrations in Example 12, Example 14, and Example 16.

[0074] Example 13 (Czochralski growth of Lu 1.795-2a Y 0.2 Ce 0.002 Ca 0.003 Mg 2a Si 0.998 Al 0.002 O5) Single crystals are grown using the Czochralski method. The molar ratio of Lu2O3:Y2O3:CeO2:CaCO3:MgO:SiO2:Al2O3 is 0.8975-a:0.1:0.002:0.003:2a:0.998:0.001 (a=0, 0.001, 0.003, 0.005). After thorough mixing, the mixture is pressed by cold isostatic pressing (pressure of 250MPa). The pressed block is placed in an iridium crucible, protected by nitrogen, and fully melted by induction heating. After seeding with a seed crystal, a single crystal of a preset size is slowly pulled from the melt to obtain Lu 1.795-2a Y 0.2 Ce 0.002 Ca 0.003 Mg 2a Si 0.998 Al 0.002 O5 single crystal. The parameters of the Czochralski method include: pulling speed of 1 to 5 mm / h and rotation speed of 3 to 10 r / min.

[0075] Table 5 shows the scintillation performance of LYSO:Ce,Ca,Al crystals with different Mg doping concentrations in Example 13.

[0076] Example 14 (Czochralski growth of Lu 1.7944-2a Y 0.2 Ce 0.002 Ca 0.003 Mg 2a Yb 0.0006 Si 0.998 Al 0.002 O5) Single crystals were grown using the Czochralski method. The molar ratio of Lu2O3:Y2O3:CeO2:CaCO3:MgO:Yb2O3:SiO2:Al2O3 was 0.8972-a:0.1:0.002:0.003:2a:0.0003:0.998:0.001 (a=0.001, 0.003, 0.005). Subsequent steps were the same as in Example 13 to obtain Lu 1.7944-2a Y 0.2 Ce 0.002 Ca 0.003 Mg 2a Yb 0.0006 Si 0.998 Al 0.002 O5 single crystal.

[0077] Example 15 (Czochralski growth of Lu 1.795-2a Y 0.2 Ce 0.002 Ca 0.003 Cu 2a Si 0.998 Al 0.002 O5) Single crystals are grown using the Czochralski method. The molar ratio of Lu2O3:Y2O3:CeO2:CaCO3:CuO:SiO2:Al2O3 is 0.8975-a:0.1:0.002:0.003:2a:0.998:0.001 (a=0, 0.001, 0.003, 0.005). After thorough mixing, the mixture is cold isostatically pressed (at a pressure of 250 MPa). The pressed block is placed in an iridium crucible, in a nitrogen atmosphere, and fully melted by induction heating. After seeding with a seed crystal, a single crystal of a predetermined size is slowly grown from the melt to obtain Lu. 1.795-2a Y 0.2 Ce 0.002 Ca 0.003 Cu 2a Si 0.998 Al 0.002 O5 single crystal. The parameters of the Czochralski method include: pulling speed of 1 to 5 mm / h and rotation speed of 3 to 10 r / min.

[0078] Table 6 shows the scintillation performance of LYSO:Ce,Ca,Al crystals with different Cu doping concentrations in Example 15.

[0079] Example 16 (Czochralski growth of Lu 1.7944-2a Y 0.2 Ce 0.002 Ca 0.003 Cu 2a Yb 0.0006 Si 0.998 Al 0.002 O5) Single crystals were grown using the Czochralski method. The molar ratio of Lu2O3:Y2O3:CeO2:CaCO3:CuO:Yb2O3:SiO2:Al2O3 was 0.8972-a:0.1:0.002:0.003:2a:0.0003:0.998:0.001 (a=0.001, 0.003, 0.005). Subsequent steps were the same as in Example 15 to obtain Lu 1.7944-2a Y 0.2 Ce 0.002 Ca 0.003 Cu 2a Yb 0.0006 Si 0.998 Al 0.002 O5 single crystal.

[0080] Through the above embodiments, combined with different compositions and different processes, the ultrafast, high-brightness and extremely low-fluorescence rare earth orthosilicate scintillating materials of the present application were prepared.

[0081] It should be noted that, in the above embodiments, only the performance of the single crystals of part of the composition of Example 5 is recorded. In fact, the single crystals obtained in the embodiments of other components and other processes all have results consistent with the conclusions of Example 5, and their redundant description is omitted here.

[0082] 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. An ultrafast, high-brightness, and extremely low-fluorescence rare earth orthosilicate scintillating material, characterized in that: The chemical formula of the ultrafast, high-brightness and extremely low-fluorescence rare earth orthosilicate scintillating material is RE 2(1-x-y-a) Ce 2x Ca 2y A 2a Si (1-z) Al z O5; Among them, 0<x≤0.05, 0<y≤0.02, 0<z≤0.05, 0≤a≤0.01; The RE represents a rare earth element, and the rare earth element is at least one selected from lanthanum, lutetium, yttrium, and gadolinium; The A represents other doping elements, and the other doping elements are selected from at least one of lithium Li, sodium Na, potassium K, rubidium Rb, cesium Cs, magnesium Mg, strontium Sr, scandium Sc, ytterbium Yb, and copper Cu.

2. The ultrafast, high-brightness, and extremely low-fluorescence rare earth orthosilicate scintillating material according to claim 1, characterized in that: The rare earth element is lutetium and / or yttrium.

3. The ultrafast, high-brightness, and extremely low-fluorescence rare earth orthosilicate scintillating material according to claim 2, characterized in that: The rare earth elements are lutetium and yttrium; wherein the molar ratio of lutetium to yttrium is (7-9):

1.

4. The ultrafast, high-brightness, and extremely low-fluorescence rare earth orthosilicate scintillating material according to claim 1, characterized in that: 0.0001≤x≤0.003, 0.001≤y<0.003, 0.001≤z≤0.

01.

5. The ultrafast, high-brightness, and extremely low-fluorescence rare earth orthosilicate scintillating material according to claim 1, characterized in that: 0.0001≤x≤0.003, 0.003≤y≤0.005, 0.001≤z≤0.

01.

6. The ultrafast, high-brightness, and extremely low-fluorescence rare earth orthosilicate scintillating material according to any one of claims 1 to 5, characterized in that: The scintillation light yield of the ultrafast, high-brightness and extremely low-fluorescence rare earth orthosilicate scintillation material is greater than 10 4 ph. / MeV, the scintillation light decay time is within 35ns, and the fluorescence response is within 5% of that of LYSO:Ce scintillation material.

7. The ultrafast, high-brightness, and extremely low-fluorescence rare earth orthosilicate scintillating material according to claim 6, characterized in that: The absorption coefficient at 358nm in the optical absorption spectrum is less than 2.5cm -1 .

8. A method for preparing an ultrafast, high-brightness, and extremely low-fluorescence rare earth orthosilicate scintillating material, characterized in that: The chemical formula of the ultrafast, high-brightness and extremely low-fluorescence rare earth orthosilicate scintillating material is RE 2(1-x-y-a) Ce 2x Ca 2y A 2a Si (1-z) Al z O5; Among them, 0<x≤0.05, 0<y≤0.02, 0<z≤0.05, 0≤a≤0.01; The RE represents a rare earth element, and the rare earth element is selected from at least one of lanthanum, lutetium, yttrium, and gadolinium; A represents other doping elements, and the other doping elements are selected from at least one of lithium Li, sodium Na, potassium K, rubidium Rb, cesium Cs, magnesium Mg, strontium Sr, scandium Sc, ytterbium Yb, and copper Cu; The ultrafast, high-brightness and extremely low-fluorescence rare earth orthosilicate scintillating material is a single crystal, and the preparation method comprises the following steps: S1, weighing rare earth oxide, CeO2, SiO2, Al2O3, oxides of other doping elements, CaCO3 or CaO as raw materials according to the chemical formula of the ultrafast, high-brightness and extremely low-fluorescence rare earth orthosilicate scintillating material, and fully mixing them to obtain a mixed powder; S2, pressing the mixed powder into a shape, and then subjecting the mixed powder to a solid phase reaction at 1000-2000° C. for 5-200 hours to obtain a polycrystalline material with a single phase composition; S3, placing the polycrystalline material into a container, heating it to melt it, and controlling the melt to slowly cool and crystallize to obtain a crude single crystal; S4, annealing the crude single crystal at 1000-1400° C. for 10-200 hours to obtain the ultrafast, high-brightness, and extremely low-fluorescence rare earth orthosilicate scintillating material.

9. The preparation method according to claim 8, characterized in that The step S4 specifically includes: placing the crude single crystal product in a muffle furnace, and introducing air or a mixed gas of an inert gas and oxygen into the muffle furnace; Next, the muffle furnace is heated to 1000-1400° C. at a heating rate of less than 300° C. / hour and kept at this temperature for 10-200 hours; Thereafter, the temperature is lowered to room temperature at a rate of less than 150° C. / hour to obtain the ultrafast, high-brightness and extremely low-fluorescence rare earth orthosilicate scintillating material.

10. Application of the ultrafast, high-brightness, and extremely low-fluorescence rare earth orthosilicate scintillating material according to any one of claims 1 to 7 in any field including mixed-field radiation detection, high-energy physics detection and particle identification, and nuclear medicine imaging.

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