A rare earth ion-doped enhanced ionization radiation luminescence low-dimensional halide scintillator and its preparation method and application

Abstract

The present invention relates to a rare earth ion-doped low-dimensional halide scintillator with enhanced ionization radiation luminescence, its preparation method and application, belonging to the technical field of scintillation materials. Aiming at the problems of poor lattice compatibility between the rare earth ion RE ionic radius and the low-dimensional halide A5B3(Cl x Br y I 1‑x‑y )8 material, the difficulty in balancing their melting points during the doping process, the easy occurrence of concentration segregation, and the difficulty in growing large-sized crystals, the present invention controls the solid solution ratio of halogen anions and the doping concentration of rare earth ions, that is, controls 0.25 ≤ x ≤ 0.875, 0 ≤ y ≤ 1, x + y ≤ 1, 0 < m < 10. At the same time, the crystal growth is carried out by the rotating and descending method, and finally a scintillator single crystal material A5B3(Cl x Br y I 1‑x‑y )8:m at% RE with advantages such as high ionization radiation luminescence efficiency and high light output is obtained, and this material can be applied to fields such as X-ray imaging, γ-ray detection, and particle detection.

Description

Technical Field

[0001] The present invention belongs to the technical field of scintillation materials, and particularly relates to a rare earth ion-doped low-dimensional halide scintillator with enhanced ionization radiation luminescence, and a preparation method and application thereof. Background Art

[0002] High-resolution X-ray imaging technology is widely used in fields such as medical imaging, industrial non-destructive testing, and homeland security. As the core component of the X-ray detection system, the detection sensitivity of the scintillation material plays a decisive role in the quality of the detection system. The currently widely used scintillation materials generally have problems such as low luminescence efficiency, easy deliquescence, strong self-absorption, and strong afterglow, and cannot meet the requirements of high-resolution imaging, low-dose detection, and real-time dynamic imaging.

[0003] In recent years, low-dimensional halides with strong confinement exciton luminescence characteristics have shown great application potential in the field of X-ray detection due to their excellent luminescence properties (high fluorescence quantum efficiency, no self-absorption) and excellent physical properties (not easy to deliquesce, low melting point). Among them, low-dimensional halides represented by Cs5Cu3Cl6I2 (orthorhombic system Cmcm) have physical properties and scintillation properties such as non-deliquescence, high effective atomic number (49), low melting point (339 °C), high light yield (49,700 photons / MeV), low detection limit (0.011 µGy air s -1 ) and low afterglow (0.1% @ 10 ms), which are far superior to existing X-ray detection materials. However, its high light yield is accompanied by a long decay time (40 μs), which limits its application in the fields of ultrafast imaging and high-resolution dynamic imaging.

[0004] In addition, due to their special electronic layer structure, rare earth elements have spectral properties that are incomparable to general elements, and rare earth luminescence plays an important role in the entire solid luminescence. The atoms of rare earth elements have unfilled and externally shielded 4f-5d electron configurations, so they have rich electronic energy levels and long-lived excited states. There are more than 200,000 energy level transition channels, which can produce a variety of radiation absorption and emission processes, thus realizing efficient luminescence. Rare earth elements are widely used in the field of scintillators. Rare earth luminescent materials represented by cerium, europium, and praseodymium are often used as luminescence center ions in scintillators, such as LaBr:Ce, LYSO:Ce, CLYC:Ce, SrI2:Eu, CLYC:Pr, etc. These rare earth-doped scintillators exhibit high light yield, excellent energy resolution, and good particle discrimination ability. Some of these scintillators are currently commercially available. However, these materials also face various problems: europium ions (Eu 2+) Doped scintillation crystals can achieve extremely high light yields, excellent energy resolutions, and fast decay times due to the allowed 5d-4f transitions. However, the strong self-absorption of their luminescence will severely deteriorate the scintillation performance of the material as the size of the scintillator increases; cerium ions (Ce 3+ ) doped scintillation crystals, such as LaBr3:Ce, CLYC:Ce, etc., have both high light yields and fast decays, but free carriers will be trapped by defects and luminesce, making the performance of the crystals have bottlenecks, and the deliquescence of the above halide scintillators themselves is difficult to suppress, making them face many limitations during use.

[0005] Therefore, the research on low-dimensional structured halide scintillation crystalline materials and their doping with rare earth ions is a frontier direction for the development of scintillation materials in the field of radiation detection. However, there are still many problems in the combination of the two: First, the lattice compatibility between the ionic radius of rare earth ions and the low-dimensional halide materials needs to be explored. Generally, the ionic radius of rare earth ions is relatively large, making it difficult to enter the lattice of halide materials, or easy to cause lattice distortion after entering, resulting in a decrease in the overall stability of the composite material (such as poor air stability, difficulty in single crystal growth, etc.); Second, rare earth ion compounds have relatively high melting points, while low-dimensional halide materials have relatively low melting points, and a suitable crystal growth process needs to be found; In addition, problems such as concentration segregation and difficulty in large-size growth brought about by introducing rare earth ions into the matrix of low-dimensional halide scintillation crystal materials during the preparation process also need to be further studied and explored. SUMMARY OF THE INVENTION

[0006] Aiming at the above technical problems, the purpose of the present invention is to provide a rare earth ion-doped enhanced ionization radiation luminescence low-dimensional halide scintillator and its preparation method and application. By combining the strong confinement effect of low-dimensional halides with the efficient luminescence of rare earth ions, the prepared scintillation material has high ionization radiation luminescence intensity, good radiation stability and air stability under X-ray excitation, providing a suitable scintillation material for low-cost and high-resolution X-ray detection technology.

[0007] In the first aspect, the present invention provides a rare earth ion-doped enhanced ionization radiation luminescence low-dimensional halide scintillator, and the chemical formula of the rare earth ion-doped enhanced ionization radiation luminescence low-dimensional halide scintillator is A5B3(Cl x Br y I 1-x-y )8: m at% RE;

[0008] Wherein: A = at least one of Rb, K, Na, Cs, B = at least one of Cu, Ag, Au, and RE is Eu 2+ 、Yb 2+ 、Ce 3+ 、Pr 3+ 、Sc3+ 、Y 3+ 、La 3+ 、Nd 3+ 、Sm 3+ 、Eu 3+ 、Gd 3+ 、Tb 3+ At least one of the rare earth ions; 0.25 ≤ x ≤ 0.875, 0 ≤ y ≤ 1, x + y ≤ 1; m represents the doping concentration of the RE rare earth ions, 0 < m < 10.

[0009] Preferably, 0.05 ≤ m ≤ 2.

[0010] In a second aspect, the present invention provides a method for preparing the above-mentioned rare earth ion-doped enhanced ionization radiation luminescent low-dimensional halide scintillator, and the preparation method includes the following steps:

[0011] (1) Weigh the halide raw materials according to the element molar ratio in the chemical formula of the rare earth ion-doped enhanced ionization radiation luminescent low-dimensional halide scintillator, place them in a crucible and vacuum seal it, and perform the first temperature increase to the melting temperature of the highest melting point raw material for pre-synthesis to obtain a pre-synthesized material;

[0012] (2) Place the crucible containing the pre-synthesized material in a crystal growth furnace, perform the second temperature increase to the melting temperature of the highest melting point raw material, and maintain the temperature at the bottom of the capillary structure of the crucible near the crystallization point temperature of the pre-synthesized material;

[0013] (3) Lower and rotate the crucible in the crystal growth furnace simultaneously to grow crystals, and perform annealing and cooling after growth to obtain the rare earth ion-doped enhanced ionization radiation luminescent low-dimensional halide scintillator.

[0014] Preferably, in step (1), the vacuum degree in the crucible is 1×10 -4 ~1×10 -3 Pa; the pre-synthesis temperature is 550 - 800 °C, and the heat preservation time is 4 - 8 hours.

[0015] Preferably, in step (2), the vacuum degree of the crystal growth furnace is ≤ 10 -3 Pa.

[0016] Preferably, in step (2), the temperature at the bottom of the capillary structure of the crucible is 280 - 600 °C.

[0017] Preferably, in step (3), the growth temperature gradient of the crystal growth furnace is 5 - 50 °C / cm.

[0018] Preferably, in step (3), the rotation rate of the crucible is > 0 and ≤ 200 r / min.

[0019] Preferably, in step (3), the crucible descends at a speed of 0.01 - 10.0 mm / h.

[0020] Thirdly, the present invention provides an application of the above-mentioned rare earth ion-doped enhanced ionization radiation luminescent halide scintillator in X-ray imaging, γ-ray detection, and particle detection.

[0021] Beneficial effects

[0022] (1) In the present invention, Eu 2+ and other ions are incorporated into matrices such as Cs5Cu3Cl6I2, and by optimizing the ion doping concentration, a significant increase in the light output relative to the intrinsic material of the undoped matrix is achieved. The optimal light output is close to 70,000 ph. / MeV. The successful introduction of europium ions and other ions enables the crystal material to have a relatively fast characteristic decay time of doped ions such as europium. The imaging line pairs of the scintillator crystal under X-rays can reach 18 lp / mm, showing excellent X-ray imaging performance;

[0023] (2) The halide scintillator based on rare earth ion doping of the present invention has advantages such as non-deliquescence, high ionization radiation luminescence efficiency, high light output, and high spatial resolution, and can be used for detecting rays or particles such as X-rays and γ-rays, and has important application prospects in the fields of medical imaging, security inspection, oil well logging, and industrial detection. Description of the drawings

[0024] Figure 1 are photos of the halide scintillator samples provided in Examples 1 - 6, 12, and Comparative Examples 1 - 5 under natural light;

[0025] Figure 2 are photos of the halide scintillator sample provided in Example 7 under natural light;

[0026] Figure 3 are photos of the halide scintillator samples prepared in Examples 8 - 11 under natural light;

[0027] Figure 4 are fluorescence emission spectra of the scintillator single crystals prepared in Examples 1 and 5;

[0028] Figure 5 are fluorescence decay diagrams of the halide scintillator samples prepared in Examples 1 and 5;

[0029] Figure 6 are X-ray imaging resolution diagrams of the scintillator single crystals prepared in Examples 1 and 5;

[0030] Figure 7 are diagrams comparing the ionization radiation luminescence intensities of the scintillator single crystals synthesized in Examples 1 - 6 and the BGO scintillator single crystal sample provided in Comparative Example 1;

[0031] Figure 8 Ionizing radiation luminescence intensity comparison chart of the scintillator samples prepared in Example 5 and Comparative Example 2;

[0032] Figure 9 Ionizing radiation luminescence intensity comparison chart of the single crystal scintillator samples prepared in Example 5 and Comparative Example 5;

[0033] Figure 10 Ionizing radiation luminescence peak type comparison chart of the halide scintillator samples prepared in Examples 1 and 7;

[0034] Figure 11 Ionizing radiation luminescence peak type comparison chart of the halide scintillator samples prepared in Examples 8 and 9;

[0035] Figure 12 Ionizing radiation luminescence peak type comparison chart of the halide scintillator samples prepared in Examples 10 and 11;

[0036] Figure 13 XRD chart of the single crystal scintillator samples synthesized in Examples 1 and 5;

[0037] Figure 14 Surface comparison chart of the halide scintillation crystals synthesized in Example 5 and Comparative Example 5 under a polarized light microscope;

[0038] Figure 15 Ionizing radiation luminescence spectrum of the halide scintillator sample prepared in Example 12. Detailed implementation manners

[0039] 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.

[0040] First, the present invention provides a rare earth ion doped enhanced ionizing radiation luminescence low-dimensional halide scintillator. Among them, the chemical formula of the rare earth ion doped enhanced ionizing radiation luminescence low-dimensional halide scintillator can be A5B3(Cl x Br y I 1-x-y )8: m at% RE; where: A = at least one of Rb, K, Na, Cs, B = at least one of Cu, Ag, Au, and RE is Eu 2+ , Yb 2+ , Ce 3+ , Pr 3+ , Sc 3+ , Y 3+ , La 3+ , Nd 3+ , Sm 3+ , Eu 3+ , Gd3+ , Tb 3+ At least one of the rare earth ions; 0.25 ≤ x ≤ 0.875, 0 ≤ y ≤ 1, x + y ≤ 1; m represents the doping concentration of the RE rare earth ions, 0 < m < 10, preferably, 0.05 ≤ m ≤ 2. It should be noted that the x and y can take any real numbers within the defined ranges.

[0041] The technical solution disclosed in the present invention proposes a strategy of combining rare earth ion doping with solid solution of halogen anions in different ratios to optimize the performance of halide scintillators: by artificially introducing hetero-valent rare earth ions into the lattice, new luminescent centers or defect energy levels are introduced, so that the carriers in the raw materials can be more effectively utilized, the proportion of non-radiative transitions is reduced, and efficient luminescence is achieved; at the same time, by regulating the doping concentration of rare earth ions, the doping concentration with the best luminescence efficiency is found to maximize the material performance. Among them, by limiting the value of m, the effective incorporation of rare earth ions can be ensured, the performance deterioration caused by concentration quenching can be avoided, and the high-quality growth of scintillation single crystals can be guaranteed. If the value of m is too large, it is easy to cause large lattice distortion of the scintillator, produce concentration quenching effects, etc., and ultimately lead to material performance deterioration or even inability to grow single crystals.

[0042] In addition, the halogen anions Cl - , Br - , I - used in the present invention have gradually increasing ionic radii (Cl - < Br - < I - ). The selection and replacement of different halogen anion species will change the lattice constants of the scintillator material, and thus affect the energy band structure of the material and the coordination environment of the luminescent ions. Specifically, Cl - has a smaller ionic radius and can allow a more compact coordination structure, making the crystal field splitting energy of the scintillator smaller (low-energy transition, red shift); while I - has a larger ionic radius, which will force Cu + and other ions to enter a higher symmetry coordination structure, increasing the crystal field splitting energy (high-energy transition, blue shift). By adjusting the solid solution ratio of the raw material halogen anions in the present invention, the emission wavelength of the material can be optimized to achieve different emission band regulations; at the same time, due to the changes in ionic radius and electronegativity, the spin-orbit coupling effect of the material can be regulated to optimize the radiative transition path. Specifically, for example: I -The 5p orbital has significant spin-orbit coupling, which can lead to the splitting of the conduction band or valence band (such as the Rashba effect), forming an energy level separation between dark states and bright states. This separation may inhibit non-radiative transitions (such as through phonon scattering) while enhancing the radiative recombination efficiency, thereby regulating the luminescence efficiency of the material and helping to achieve efficient luminescence and energy transfer between luminescence centers.

[0043] Furthermore, the present invention can ensure a suitable solid solution ratio between halogen anions by limiting the values of x and y. When the ratio of halogen atoms is unbalanced, it will have a significant impact on crystal growth, luminescence performance, etc. In particular, if the value of x is too large or too small, it will cause a large lattice distortion to the scintillator material. If the value of x is too large, the scintillator material will undergo a phase transition and deteriorate the material performance; if x is too small, it will make it difficult to grow a single crystal of the material.

[0044] In some embodiments, the rare earth ion doped enhanced ionizing radiation luminescence low-dimensional halide scintillator belongs to the orthorhombic system, Cmcm space group, and the range of its unit cell parameters a, b, c can be: 16.7 Å<a<17.2 Å, 8.9 Å<b<9.4 Å, 13.8 Å<c<14.3 Å. By controlling the unit cell parameters within this limit, it is possible to avoid large lattice distortion of the material and affect the crystal coordination structure.

[0045] In some embodiments, the rare earth ion doping enhanced ionizing radiation luminescence low-dimensional halide scintillator can be in the form of a single crystal block; preferably, the rare earth ion doping enhanced ionizing radiation luminescence low-dimensional halide scintillator single crystal has a size of not less than 4 mm in at least one dimension.

[0046] In some embodiments, the decay time of the rare earth ion doped ionizing radiation luminescence low-dimensional halide scintillator may be 500 to 1000 ns, preferably 600 to 700 ns, and more preferably 671 ns.

[0047] In some embodiments, the light yield of the rare earth ion doped enhanced ionizing radiation luminescence low-dimensional halide scintillator can be 40,000 to 70,000 ph. / MeV, preferably 49,000 to 70,000 ph. / MeV, and more preferably 69,700 ph. / MeV.

[0048] In some embodiments, the X-ray imaging line log number of the rare earth ion doped enhanced ionizing radiation luminescence low-dimensional halide scintillator can reach 14 to 18 lp / mm, preferably 18 lp / mm.

[0049] In summary, in the present invention, hetero-valent rare earth ions are artificially introduced into the low-dimensional halide lattice to form new defect luminescence centers. Through the competition between rare earth ion luminescence and intrinsic luminescence, or the formation of excitonic luminescence bound by rare earth ions, or the existence of energy transfer effects between two luminescence centers, etc., the light yield and decay time of the scintillator can be further optimized, the problem of slow intrinsic decay time of the material can be solved, and ultimately the realization of high-sensitivity, low-radiation-dose, and high-spatial-resolution X-ray imaging can be promoted.

[0050] Hereinafter, a preparation method of a rare earth ion-doped low-dimensional halide scintillator with enhanced ionizing radiation luminescence provided by the present invention will be exemplarily described. Among them, the preparation method may include the following steps:

[0051] (1) Weigh the halide raw materials according to the element molar ratio in the chemical formula of the rare earth ion-doped low-dimensional halide scintillator, place them in a crucible and perform vacuum sealing. Heat the crucible to the melting temperature of the highest melting point raw material for the first time in a vacuum environment and mix them evenly for pre-synthesis. After the molten liquid becomes a homogeneous and clear liquid, cool it down to obtain a pre-synthesized material.

[0052] (2) Vertically place the crucible containing the pre-synthesized material in a high-vacuum crystal growth furnace. Heat the pre-synthesized material in the crucible to the melting temperature of the highest melting point raw material for the second time, and adjust the furnace temperature and the position of the crucible so that the temperature at the bottom of the capillary structure of the crucible is maintained near the crystallization point temperature of the pre-synthesized material.

[0053] (3) Adjust the crucible to a suitable temperature gradient in the crystal growth furnace, and at the same time rotate and lower it to carry out crystal growth. After annealing and cooling, the rare earth ion-doped low-dimensional halide scintillator is obtained.

[0054] In some embodiments, in step (1), the halide raw materials may include CsCl, CsBr, CuCl, CuI, CeI3, EuI2, PrI3, YbI2; preferably, the purity of the halide raw materials may be ≥99.99 wt%.

[0055] In some embodiments, in step (1), the temperature of the pre-synthesis may be 550-800 °C, and the holding time may be 4-8 hours; preferably, the vacuum degree of the pre-synthesis may be 1×10 -4 ~1×10 -3 Pa. If the temperature is too low, the melting point of the raw material cannot be reached, and if the temperature is too high, the halide raw materials are likely to volatilize and decompose.

[0056] In some embodiments, in step (2), the vacuum degree of the high-vacuum crystal growth furnace may be ≤10 -3 Pa.

[0057] In some embodiments, in step (2), the temperature at the bottom of the capillary structure of the crucible can be the crystallization point temperature of the pre-synthesized material ±10°C, preferably 280 - 600°C.

[0058] It should be noted that in step (2), with the assistance of the observation window and the temperature-measuring thermocouple, the position of the crucible and the temperature inside the furnace can be finely adjusted to ensure that the temperature at the bottom of the capillary structure of the crucible is maintained near the crystallization point temperature of the material. During this process, partial crystallization should start to form at the capillary bottom. At the same time, the high vacuum condition reduces the interference of gas convection on the uniformity of the thermal field, helps to form a stable temperature gradient, and helps to control the liquid-solid interface morphology and crystal growth rate.

[0059] In addition, in the preparation method disclosed in the present invention, the first temperature increase can fully melt and mix the raw materials to obtain a polycrystalline target product; the second temperature increase can cause secondary mixing of the raw materials. The two melting and mixing processes help to improve the quality of the final crystal growth, reduce the formation of defects, and ensure the uniformity of the crystal components.

[0060] In some embodiments, in step (3), the growth temperature gradient of the crystal growth furnace can be 5 - 50°C / cm. If the temperature gradient is too large, it is easy to cause the accumulation of thermal stress and lead to crystal cracking; if the temperature gradient is too small, it will weaken the driving force for crystal growth and affect the quality of the crystal.

[0061] In some embodiments, in step (3), the rotation rate of the crucible can be >0 and ≤200 r / min.

[0062] Among them, slowly rotating and lowering the crucible in the crystal growth furnace can, through the centrifugal force of rotation, promote the movement of internal molecules in the melt, reduce the radial temperature gradient in the melt, and reduce local supercooling or overheating caused by uneven temperature gradients, which is beneficial to the stability of the solid-liquid interface. At the same time, it helps to evenly disperse the dopants in the melt and effectively suppress the segregation phenomenon caused by the dopants in the melt for high-quality single crystal growth. It should be noted that an appropriate rotation rate should be selected during crystal growth. If the rotation rate is too large or too small, it will affect the crystal quality. If it is too large, it is easy to cause excessive disturbance of the melt and instability of the interface; if it is too small, the solute diffusion will be limited and the effect of suppressing segregation cannot be achieved.

[0063] In some embodiments, in step (3), the lowering speed of the crucible can be 0.01 - 10.0 mm / h. In this way, it can ensure that the solid-liquid interface of the crucible is always in a stable state. In addition, during the crystal growth process, a high-resolution CCD camera can be used to closely observe the morphology of the crystal-melt interface, and according to the observed interface morphology, the lowering rate of the crucible can be adjusted in real time and dynamically. By monitoring the crystallization situation during the crystal lowering process in real time and dynamically adjusting the furnace temperature field, an appropriate temperature gradient can be maintained to ensure the integrity and transparency of crystal growth.

[0064] In some embodiments, in step (3), the cooling rate during annealing can be 0.1 to 50 °C / h. After the crystal growth is completed, the method of annealing and cooling can maximize the release of the internal stress of the crystal to avoid cracking of the crystal during subsequent processing.

[0065] In summary, the present invention uses the Bridgman descending method with simple operation to efficiently grow transparent, inclusion-free, and high-quality scintillation single crystals. The slow cooling method with controllable temperature field movement or temperature field distribution can also be used as a preferred preparation method.

[0066] The rare earth ion-doped enhanced ionization radiation-emitting halide scintillator obtained by the preparation method provided by the present invention can be applied in X-ray imaging, γ-ray detection, and particle detection, including applications in medical imaging, security inspection, oil well logging, and industrial detection. Among them, when applied in high-resolution X-ray imaging, the line pairs of the crystal imaging under X-rays can be provided.

[0067] The following further gives examples 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 construed as limiting the protection scope of the present invention. Those skilled in the art's non-essential improvements and adjustments made based on the above content of the present invention all fall within the protection scope of the present invention. The specific process parameters and the like in the following examples are also only an example within a suitable range, that is, those skilled in the art can make selections within a suitable range through the description in this article, rather than being limited to the specific values in the following examples. If not specifically specified, the technical means used in the examples are conventional means well known to those skilled in the art.

[0068] Unless otherwise specified, in the present invention:

[0069] (1) Use a tungsten target X-ray tube as the excitation source and an Ocean Optics QEpro spectrometer as the detector to test the ionization radiation luminescence performance of the obtained rare earth ion-doped enhanced ionization radiation-emitting halide scintillator;

[0070] (2) Use a Horiba Jobin Yvon Fluorolog-3 fluorescence spectrometer as the excitation source and the detector to test the photoexcitation and emission spectra of the obtained rare earth ion-doped enhanced ionization radiation-emitting halide scintillator;

[0071] (3) Use a Bruker D8 high-resolution powder X-ray diffractometer to test the X-ray diffraction pattern of the obtained rare earth ion-doped enhanced ionization radiation-emitting halide scintillator.

[0072] Example 1

[0073] The preparation method of the low-dimensional halide scintillator Cs5Cu3Cl6I2 (A = Cs, B = Cu, x = 0.75, y = 0, m = 0) provided in this embodiment includes the following steps:

[0074] (1) Weigh the halide raw materials according to the element molar ratio in Cs5Cu3Cl6I2. In a glove box filled with argon or nitrogen, mix the raw materials evenly and transfer them to a quartz crucible with a capillary about 2 cm long. Pump the inside of the crucible to a vacuum of 10 -4 Pa and seal it by welding; move the sealed quartz crucible to a crucible rack and let it stand still; during this period, use an electric spark gun vacuum detector to conduct a contact test on the crucible. The appearance of a glow discharge phenomenon indicates that the inside of the crucible is in a vacuum environment and the crucible is successfully welded; transfer the welded crucible to a tube furnace for material pre-synthesis. Heat it up to 600 °C in a vacuum environment to melt the mixed raw materials. After melting, rotate to make the raw materials mix evenly. Keep this state for 5 hours. After observing that the molten liquid is a homogeneous and clear liquid, complete the pre-synthesis and slowly cool it with the furnace to obtain the pre-synthesized material;

[0075] (2) Vertically place the crucible containing the pre-synthesized material in a high-vacuum crystal transparent growth furnace and adjust it to a suitable position; control the vacuum degree in the furnace ≤ 10 -3 Pa, conduct a second heating on the pre-synthesized material. The temperature in the furnace rises from room temperature to 600 °C in 8 hours, melting the pre-synthesized material for the second time. With the assistance of the observation window and the temperature-measuring thermocouple, finely adjust the position of the crucible and the temperature field in the furnace to ensure that the temperature at the bottom of the capillary structure of the crucible is maintained near the crystallization point temperature of the material. During this process, some crystallization should start to form at the bottom of the capillary;

[0076] (3) Slowly rotate and lower the crucible in the crystal growth furnace, and set the rotation speed to 30 r / min; during the growth process, use a high-resolution CCD camera to closely observe the morphology of the crystal-melt interface. According to the observed interface morphology, dynamically adjust the lowering rate of the crucible in real time. The initial lowering rate is set to 0.5 mm / h to ensure that the solid-liquid interface of the crucible is always in a stable state; at the same time, monitor the crystallization situation during the crystal lowering process in real time and dynamically adjust the furnace temperature field to maintain an appropriate temperature gradient to ensure the integrity and transparency of crystal growth; after the crystal growth is completed, adopt an annealing and cooling method to release the stress inside the crystal to the greatest extent to avoid cracking of the crystal during the growth process and subsequent processing. The cooling rate is set to 5 °C / h. After the cooling treatment, a single-crystal form of the low-dimensional halide scintillator Cs5Cu3Cl6I2 is obtained.

[0077] After testing, the Cs5Cu3Cl6I2 halide scintillator obtained in Example 1 has good crystallinity and radiation stability, is non-deliquescent, and has no self-absorption effect. Its congruent melting property has obvious advantages for the growth of large-sized crystals. The light yield was evaluated to be 49,000 photons / MeV under steady-state X-rays.

[0078] Example 2

[0079] The rare-earth ion-doped low-dimensional halide scintillator Cs5Cu3Cl6I2:0.1%Eu provided in this example 2+ (A = Cs, B = Cu, x = 0.75, y = 0, m = 0.1, RE = Eu 2+ ) was prepared with reference to Example 1, and the main difference is that:

[0080] In step (1), the halide raw materials were weighed according to the elemental molar ratio in Cs5Cu3Cl6I2:0.1% Eu 2+ .

[0081] After testing, the Cs5Cu3Cl6I2:0.1% Eu 2+ halide scintillator has good crystallinity and radiation stability, is non-deliquescent, has a small self-absorption effect, and its congruent melting property has obvious advantages for the growth of large-sized crystals. The light yield was evaluated to be 60,000 photons / MeV under steady-state X-rays, and the light yield increased by 22% compared with the undoped crystal.

[0082] Example 3

[0083] The rare-earth ion-doped low-dimensional halide scintillator Cs5Cu3Cl6I2:0.2% Eu provided in this example 2+ (A = Cs, B = Cu, x = 0.75, y = 0, m = 0.2, RE = Eu 2+ ) was prepared with reference to Example 1, and the main difference is that:

[0084] In step (1), the halide raw materials were weighed according to the elemental molar ratio in Cs5Cu3Cl6I2:0.2% Eu 2+ .

[0085] After testing, the Cs5Cu3Cl6I2:0.2% Eu 2+ halide scintillator has good crystallinity and radiation stability, is non-deliquescent, has a small self-absorption effect, and its congruent melting property has obvious advantages for the growth of large-sized crystals. The light yield was evaluated to be 62,000 photons / MeV under steady-state X-rays, and the light yield increased by 26% compared with the undoped crystal.

[0086] Example 4

[0087] The rare earth ion-doped enhanced ionization radiation-emitting low-dimensional halide scintillator Cs5Cu3Cl6I2: 0.5% Eu provided in this example 2+ (A = Cs, B = Cu, x = 0.75, y = 0, m = 0.5, RE = Eu 2+ )has a preparation method referring to Example 1, and the main difference is that:

[0088] In step (1), the halide raw materials are weighed according to the element molar ratio in Cs5Cu3Cl6I2: 0.5% Eu 2+ among them.

[0089] After testing, the Cs5Cu3Cl6I2: 0.5% Eu 2+ halide scintillator obtained in Example 4 has good crystallinity and radiation stability, is not deliquescent, has a small self-absorption effect, and its congruent melting property has obvious advantages for large-size crystal growth. The light yield evaluated under steady-state X-rays is 67,000 photons / MeV, and the light yield is increased by 36% compared with the undoped crystal.

[0090] Example 5

[0091] The rare earth ion-doped enhanced ionization radiation-emitting low-dimensional halide scintillator Cs5Cu3Cl6I2: 1.0% Eu provided in this example 2+ (A = Cs, B = Cu, x = 0.75, y = 0, m = 1.0, RE = Eu 2+ )has a preparation method referring to Example 1, and the main difference is that:

[0092] In step (1), the halide raw materials are weighed according to the element molar ratio in Cs5Cu3Cl6I2: 1.0% Eu 2+ among them.

[0093] After testing, the Cs5Cu3Cl6I2: 1.0% Eu 2+ halide scintillator obtained in Example 5 has good crystallinity and radiation stability, is not deliquescent, has a small self-absorption effect, and its congruent melting property has obvious advantages for large-size crystal growth. The light yield evaluated under steady-state X-rays is 69,700 photons / MeV, and the light yield is increased by 42% compared with the undoped crystal.

[0094] Example 6

[0095] The rare earth ion-doped enhanced ionization radiation-emitting low-dimensional halide scintillator Cs5Cu3Cl6I2: 2.0% Eu provided in this example 2+(where A = Cs, B = Cu, x = 0.75, y = 0, m = 2.0, RE = Eu 2+ ) The preparation method refers to Example 1, with the main difference being:

[0096] In step (1), weigh the halide raw materials according to the element molar ratio in Cs5Cu3Cl6I2: 2.0% Eu 2+ .

[0097] After testing, the Cs5Cu3Cl6I2: 2.0% Eu 2+ halide scintillator obtained in Example 6 has good crystallinity, radiation stability, is non-deliquescent, has a small self-absorption effect, and its congruent melting property has obvious advantages for large-size crystal growth. Due to the concentration quenching effect, its light yield evaluated under steady-state X-rays is 52,000 photons / MeV, and the light yield is increased by 6% compared with the undoped crystal.

[0098] Example 7

[0099] The rare-earth ion-doped enhanced ionization radiation-emitting low-dimensional halide scintillators Cs5Cu3Cl6I2: 1.0% Pr 3+ , Cs5Cu3Cl6I2: 1.0% Ce 3+ , Cs5Cu3Cl6I2: 1.0% Yb 2+ (where A = Cs, B = Cu, x = 0.75, y = 0, m = 1.0, RE = Pr 3+ , Ce 3+ , Yb 2+ in one of them) The preparation method refers to Example 1, with the main difference being:

[0100] In step (1), weigh the halide raw materials according to the element molar ratio in Cs5Cu3Cl6I2: 1.0% Pr 3+ , Cs5Cu3Cl6I2: 1.0% Ce 3+ , Cs5Cu3Cl6I2: 1.0% Yb 2+ respectively.

[0101] After testing, the Cs5Cu3Cl6I2: 1.0% Pr 3+ , Cs5Cu3Cl6I2: 1.0% Ce 3+ , Cs5Cu3Cl6I2: 1.0% Yb 2+ halide scintillators have high-performance ionization radiation-emitting properties and can be used in fields such as X-ray imaging and γ-ray detection.

[0102] Example 8

[0103] The preparation method of the low-dimensional halide scintillator Cs5Cu3Cl6Br2 (A = Cs, B = Cu, x = 0.75, y = 0.25, m = 0) provided in this example refers to Example 1, and the main difference is that:

[0104] In step (1), the halide raw materials are weighed according to the elemental molar ratio in Cs5Cu3Cl6Br2.

[0105] After testing, the Cs5Cu3Cl6Br2 halide scintillation crystal obtained in Example 8 has a strong radiation luminescence response. The ionization radiation luminescence spectrum shows that it has high-efficiency ionization radiation luminescence performance, and the luminescence peak is located at 480 nm.

[0106] Example 9

[0107] The rare-earth ion-doped enhanced ionization radiation luminescence low-dimensional halide scintillator Cs5Cu3Cl6Br2: 1.0% Eu 2+ (A = Cs, B = Cu, x = 0.75, y = 0.25, m = 1.0, RE = Eu 2+ ) provided in this example refers to Example 1, and the main difference is that:

[0108] In step (1), the halide raw materials are weighed according to the elemental molar ratio in Cs5Cu3Cl6Br2: 1.0% Eu 2+ in.

[0109] After testing, the Cs5Cu3Cl6Br2: 1.0% Eu 2+ halide scintillation crystal obtained in Example 9 has two luminescence centers. On the basis of the original luminescence, the characteristic luminescence of Eu 2+ appears. The luminescence peak is located at 450 nm, and the peak intensity is higher than the original luminescence peak located at 480 nm. The ionization radiation luminescence spectrum shows that it has high-efficiency ionization radiation luminescence performance.

[0110] Example 10

[0111] The preparation method of the low-dimensional halide scintillator Cs5Cu3Cl6BrI (A = Cs, B = Cu, x = 0.75, y = 0.125, m = 0) provided in this example refers to Example 1, and the main difference is that:

[0112] In step (1), the halide raw materials are weighed according to the elemental molar ratio in Cs5Cu3Cl6BrI.

[0113] After testing, the Cs5Cu3Cl6BrI halide scintillation crystal obtained in Example 10 has a strong radiation luminescence response. The ionization radiation luminescence spectrum shows that it has high-efficiency ionization radiation luminescence performance, and the luminescence peak is located at 520 nm.

[0114] Example 11

[0115] The rare earth ion-doped enhanced ionization radiation luminescence low-dimensional halide scintillator Cs5Cu3Cl6BrI: 1.0% Eu provided in this example 2+ (A = Cs, B = Cu, x = 0.75, y = 0.125, m = 1.0, RE = Eu 2+ )is prepared with reference to Example 1, and the main difference is that:

[0116] In step (1), the halide raw materials are weighed according to the element molar ratio in Cs5Cu3Cl6BrI: 1.0% Eu 2+ .

[0117] After testing, the Cs5Cu3Cl6BrI: 1.0% Eu 2+ halide scintillator obtained in Example 11 has two luminescence centers, and characteristic luminescence of Eu appears on the basis of the original luminescence. The luminescence peak is located at 470 nm, and the original luminescence peak is located at 520 nm. The ionization radiation luminescence spectrum shows that it has high-performance ionization radiation luminescence performance. 2+

[0118] Example 12

[0119] The rare earth ion-doped enhanced ionization radiation luminescence low-dimensional halide scintillator Cs5Cu3Cl7I1: 1.0% Eu provided in this example 2+ (A = Cs, B = Cu, x = 0.875, y = 0, m = 1.0, RE = Eu 2+ )is prepared with reference to Example 1, and the main difference is that:

[0120] In step (1), the halide raw materials are weighed according to the element molar ratio in Cs5Cu3Cl7I1: 1.0% Eu 2+ .

[0121] After testing, the Cs5Cu3Cl7I1: 1.0% Eu 2+ halide scintillator obtained in Example 12 has two luminescence centers, and the luminescence peaks are located at 470 nm and 523 nm respectively. It shows cold white luminescence under ultraviolet light, and the ionization radiation luminescence spectrum shows that it has high-performance ionization radiation luminescence performance.

[0122] Comparative Example 1

[0123] This comparative example provides a standard sample scintillator, the form of which is a massive single crystal, and the chemical formula composition of this scintillator is Bi4Ge3O 12 , which is used as a comparative standard sample for the steady-state light yield of X-rays, and the default light yield is 8,000 photons / MeV. ​

[0124] Comparative Example 2

[0125] The scintillator Cs5Cu3Cl6I2:10.0%Eu provided in this comparative example 2+ (A = Cs, B = Cu, x = 0.75, y = 0, m = 10.0, RE = Eu 2+ )was prepared with reference to Example 1, and the main difference is that:

[0126] In step (1), the halide raw materials were weighed according to the elemental molar ratio in Cs5Cu3Cl6I2:10.0%Eu 2+ .

[0127] After testing, the quality of the scintillator single crystal obtained in Comparative Example 2 was poor. And due to the high doping concentration of europium ions, the concentration quenching effect caused the light yield to decrease. Its light yield was evaluated to be 30,000 photons / MeV, and the scintillation performance deteriorated severely.

[0128] Comparative Example 3

[0129] The scintillator Cs5Cu3Cl1I7:1.0%Eu provided in this comparative example 2+ (A = Cs, B = Cu, x = 0.125, y = 0, m = 1.0, RE = Eu 2+ )was prepared with reference to Example 1, and the main difference is that:

[0130] In step (1), the halide raw materials were weighed according to the elemental molar ratio in Cs5Cu3Cl1I7:1.0%Eu 2+ .

[0131] After testing, due to the imbalance of the chlorine-iodine ratio in this comparative example, the crystallinity of the finally prepared scintillator material was poor, and high-quality single crystals were not prepared by the Bridgman method.

[0132] Comparative Example 4

[0133] The scintillator Cs5Cu3Cl8:1.0%Eu provided in this comparative example 2+ (A = Cs, B = Cu, x = 1, y = 0, m = 1.0, RE = Eu 2+ )was prepared with reference to Example 1, and the main difference is that:

[0134] In step (1), the halide raw materials were weighed according to the elemental molar ratio in Cs5Cu3Cl8:1.0%Eu 2+ .

[0135] After testing, after all halogen atoms were replaced with chlorine, the material had a certain crystallinity, and high-quality single crystals could be prepared by the Bridgman method. However, a phase change occurred during the cooling process of the material, resulting in crystal pulverization and serious deterioration of the scintillation performance. The light yield could not be evaluated, and the powder XRD results showed that the matrix composition was biased towards Cs3Cu2Cl5.

[0136] Comparative Example 5

[0137] The scintillator Cs5Cu3Cl6I2: 1.0% Eu provided in this comparative example 2+ The preparation method includes the following steps:

[0138] Weigh the halide raw materials according to the element molar ratio in Cs5Cu3Cl6I2: 1.0% Eu 2+ In a glove box filled with argon or nitrogen, mix the raw materials evenly and transfer them to a quartz crucible with a capillary about 2 cm long. Evacuate the crucible and seal it by welding;

[0139] (2) Vertically place the sealed quartz crucible at the center position inside the crystal growth furnace; heat up the crystal growth furnace so that the temperature reaches 600 °C from room temperature in 8 hours, and keep it at this temperature for 24 hours to completely melt and mix the raw materials evenly. Adjust the height position of the crucible and the furnace temperature so that the temperature at the capillary tip of the crucible drops to 310 °C;

[0140] (3) Let the quartz crucible descend relative to the furnace body at a speed of 0.5 mm / h. The crystal nucleates at the capillary tip of the crucible, and gradually solidifies towards the tail end during the descent until the melt is completely crystallized, and then it is cooled to room temperature at a rate of 5 °C / h to obtain the scintillator Cs5Cu3Cl6I2: 1.0% Eu 2+ .

[0141] After testing, the crystal material prepared in Comparative Example 5 contained more inclusions, had poor transparency, and there was a large difference in luminescence between the front end and the tail end of the crystal. The light yield was evaluated at the middle position to be 50,000 photons / MeV.

[0142] The following Table 1 shows the relative light yield data of the halide scintillators prepared in Examples 1-6 and Comparative Examples 1, 2, and 5:

[0143]

[0144] Figure 1Photographs of the halide scintillator samples provided in Examples 1-6, 12, and Comparative Examples 1-5 under natural light. As can be seen from the figures, within a certain concentration range of rare-earth doped ions, the grown single-crystal samples have high optical quality. However, when the doping concentration is high, it is difficult to grow high-quality crystals. The ratio of halogen anions can grow high-quality single crystals within a certain range, but exceeding the range will cause large lattice distortion and it is difficult to grow high-quality single crystals.

[0145] Figure 2 Photograph of the halide scintillator sample provided in Example 7 under natural light. As can be seen from the figure, the sample material prepared in Example 7 has good crystallinity and transparency, and the overall crystal has good optical quality.

[0146] Figure 3 Photographs of the halide scintillator samples prepared in Examples 8-11 under natural light. As can be seen from the figures, the sample materials prepared in Examples 8-11 have good crystallinity and transparency, and the overall has good optical quality.

[0147] Figure 4 Fluorescence emission spectra of the scintillator single crystals prepared in Examples 1 and 5. As can be seen from the figure, the emission spectrum of the scintillator single crystal prepared in Example 1 under 300 nm excitation is a typical broad-spectrum emission of self-trapped excitons, and the emission peak is located at 470 nm; the emission spectrum of the scintillator single crystal prepared in Example 5 under 370 nm excitation is the narrow-spectrum emission of europium ions, and the emission peak position has no obvious shift.

[0148] Figure 5 Fluorescence decay diagrams of the halide scintillator samples prepared in Examples 1 and 5. As can be seen from the figure, the synthesized scintillator single crystal in Example 5 has a faster characteristic decay time of 671 ns for europium ions and a slower decay time of 39 μs for the self-trapped exciton luminescence itself.

[0149] Figure 6 X-ray imaging resolution diagrams of the scintillator single crystals prepared in Examples 1 and 5. As can be seen from the figure, the scintillator single crystal prepared in Example 5 has a high imaging resolution, which can reach 18 lp / mm.

[0150] By subjecting the scintillator samples prepared in Examples 1-6 and the BGO crystal in Comparative Example 1 to X-ray ionization radiation excitation and collecting and comparing spectral data using a fluorescence spectrometer, different europium doping amounts of Cs5Cu3Cl6I2: Eu 2+ Comparison of the ionization radiation luminescence intensities of the scintillators. Figure 7Comparison chart of the ionization radiation luminescence intensities of the scintillation single crystals synthesized in Examples 1-6 and the BGO scintillation single crystal sample provided in Comparative Example 1. It can be seen from the figure that when the europium doping amount in Example 5 is 1.0%, the luminescence efficiency is relatively the best, and its relative light yield calculation reaches 69,700 photons / MeV, which is 42% higher than that in Example 1.

[0151] Figure 8 Comparison chart of the ionization radiation luminescence intensities of the scintillator samples prepared in Example 5 and Comparative Example 2. It can be seen from the figure that excessive rare earth element doping will deteriorate the ionization radiation luminescence performance of the scintillator, and there is no obvious change in the peak position of the emission peak. The light yield of Comparative Example 2 is evaluated to be 30,000 photons / MeV.

[0152] Figure 9 Comparison chart of the ionization radiation luminescence intensities of the scintillation single crystal samples prepared in Example 5 and Comparative Example 5. It can be seen from the figure that the ionization radiation luminescence intensity of the single crystal sample prepared by the rotation and descent in a vacuum transparent furnace is higher than that of the sample prepared by the traditional descent process, and there is no obvious change in the peak position of the emission peak.

[0153] Figure 10 Comparison chart of the ionization radiation luminescence peak shapes of the halide scintillator samples prepared in Examples 1 and 7. It can be seen from the figure that Cs5Cu3Cl6I2: 1.0% Pr 3+ and Cs5Cu3Cl6I2: 1.0% Ce 3+ have emission peaks at 480 nm, and their peak shapes are similar. Cs5Cu3Cl6I2: 1.0% Yb 2+ has an emission peak at 472 nm, showing an overall blue shift. All three have high ionization radiation luminescence performance.

[0154] Figure 11 Comparison chart of the ionization radiation luminescence peak shapes of the halide scintillator samples prepared in Examples 8 and 9. It can be seen from the figure that the halide scintillator prepared in Example 9 has the characteristic luminescence of europium ions and the luminescence of self-trapped excitons. The emission peak positions are at 450 nm and 480 nm respectively.

[0155] Figure 12 Comparison chart of the ionization radiation luminescence peak shapes of the halide scintillator samples prepared in Examples 10 and 11. It can be seen from the figure that the halide scintillator prepared in Example 11 has the characteristic luminescence of europium ions and the luminescence of self-trapped excitons. The emission peak positions are at 470 nm and 520 nm respectively.

[0156] Figure 13 XRD patterns of the scintillation single crystal samples synthesized in Examples 1 and 5. It can be seen from the figure that the samples synthesized in Example 1 and Example 5 are of the same phase.

[0157] Figure 14 It is a surface contrast diagram of the halide scintillation crystal synthesized in Example 5 and Comparative Example 5 under a polarized light microscope. It can be seen from the figure that the surface of the single crystal prepared by the growth method of Example 5 is relatively flat and has a relatively high overall transparency (the scratches are caused by the polishing process). The surface of the single crystal prepared by the growth method of Comparative Example 5 has more holes, inclusions inside, relatively poor overall transparency, and there is a second phase present.

[0158] Figure 15 It is the ionization radiation luminescence spectrum diagram of the halide scintillator sample prepared in Example 12. It can be seen from the figure that it has two luminescence centers, namely the characteristic luminescence of europium ions and the intrinsic self-trapped exciton luminescence, and the luminescence peaks are located at 470 nm and 523 nm respectively.

[0159] Although the content of the present invention has been introduced in detail through the above preferred embodiments, it should be recognized that the above description should not be considered as a limitation to the present invention. After those skilled in the art have read the above content, various modifications and substitutions to the present invention will be obvious. Therefore, the protection scope of the present invention should be defined by the appended claims.

Claims

1. A rare earth ion-doped low-dimensional halide scintillator with enhanced ionization radiation luminescence, characterized in that, The chemical formula of the rare earth ion-doped enhanced ionization radiation luminescence low-dimensional halide scintillator is A5B3(Cl x Br y I 1-x-y )8: m at% RE; Among them: A = Cs, B = Cu, and RE is Eu 2+ , Yb 2+ , Ce 3+ , Pr 3+ , Sc 3+ , Y 3+ , La 3+ , Nd 3+ , Sm 3+ , Eu 3+ , Gd 3+ , Tb 3+ at least one of rare earth ions; 0.25 ≤ x ≤ 0.875, 0 ≤ y ≤ 1, x + y ≤ 1; m represents the doping concentration of RE rare earth ions, 0 < m < 10.

2. The rare-earth ion-doped enhanced ionization radiation luminescence low-dimensional halide scintillator according to claim 1, characterized in that, 0.05≤m≤2。 3. A method for preparing a rare earth ion-doped enhanced ionization radiation luminescent low-dimensional halide scintillator according to claim 1, characterized in that, The preparation method comprises the following steps: (1) Weigh the halide raw materials according to the element molar ratio in the chemical formula of the rare earth ion-doped enhanced ionization radiation luminescent low-dimensional halide scintillator described in claim 1, place them in a crucible, and vacuum seal it. Then, perform the first temperature increase to the melting temperature of the raw materials at the highest melting point for pre-synthesis to obtain a pre-synthesized material. (2) Place the crucible containing the pre-synthesized material in a crystal growth furnace, perform the second temperature increase to the melting temperature of the raw materials at the highest melting point, and maintain the temperature at the bottom of the capillary structure of the crucible near the crystallization point temperature of the pre-synthesized material. (3) Lower and rotate the crucible in the crystal growth furnace simultaneously to grow the crystal. After the growth is completed, perform annealing and cooling to obtain the rare earth ion-doped enhanced ionization radiation luminescent low-dimensional halide scintillator.

4. The preparation method according to claim 3, characterized in that, In step (1), the vacuum degree in the crucible is 1×10 -4 ~1×10 -3 Pa; the temperature for pre-synthesis is 550 - 800 °C, and the heat preservation time is 4 - 8 hours.

5. The preparation method according to claim 3, characterized in that, In step (2), the vacuum degree of the crystal growth furnace ≤ 10 -3 Pa.

6. The preparation method according to claim 3, characterized in that, In step (2), the temperature at the bottom of the capillary structure of the crucible is 280 - 600 °C.

7. The preparation method according to claim 3, characterized in that, In step (3), the growth temperature gradient of the crystal growth furnace is 5 - 50 °C / cm.

8. The preparation method according to claim 3, wherein In step (3), the rotation rate of the crucible is >0 and ≤200 r / min.

9. The preparation method according to claim 3, wherein In step (3), the descending speed of the crucible is 0.01 - 10.0 mm / h.

10. Application of the rare earth ion-doped enhanced ionization radiation luminescent low-dimensional halide scintillator described in claim 1 in X-ray imaging, γ-ray detection, and particle detection.

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