Rare earth ion doped enhanced ionizing radiation luminescence low-dimensional halide scintillator and preparation method and application thereof

Abstract

The invention relates to a rare earth ion doped enhanced ionizing radiation luminescence low-dimensional halide scintillator and a preparation method and application thereof, and belongs to the technical field of scintillating materials. Aiming at the problems that the radiuses of RE ions and low-dimensional halide A5B3 (ClxBryI1-x-y) 8 materials are poor in lattice adaptation degree, the melting points of the RE ions and the low-dimensional halide A5B3 (ClxBryI1-x-y) 8 materials are difficult to consider in the doping process, concentration segregation is easy to occur and large-size crystals are difficult to grow, the solid-solution ratio of halogen anions and the doping concentration of the rare earth ions are regulated and controlled, namely 0.25 < = x < = 0.875, 0 < = y < = 1, x + y < = 1 and 0 < m < 10 are controlled; meanwhile, a rotation descent method is adopted for crystal growth, the scintillator single crystal material A5B3 (ClxBryI1-x-y) 8: m at% RE with the advantages of high ionizing radiation luminous efficiency, high light output and the like is finally obtained, and the material can be applied to the fields of X-ray imaging, gamma-ray detection, particle detection and the like.

Description

Technical Field

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

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

[0003] In recent years, low-dimensional halides with strong confined exciton luminescence properties 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 (non-deliquescent, low melting point). Among them, low-dimensional halides represented by Cs5Cu3Cl6I2 (orthorhombic system Cmcm) have non-deliquescent, high effective atomic number (49), low melting point (339℃), high light yield (49,700 photons / MeV), low detection limit (0.011 µGy air s -1 ) and low afterglow (0.1%@10ms), which are far superior to existing X-ray detection materials. However, its high light yield is accompanied by a long decay time (40μs), which limits its application in ultrafast imaging and high-resolution dynamic imaging.

[0004] In addition, due to their special electronic layer structure, rare earth elements have spectral properties that cannot be matched by general elements. Rare earth luminescence plays an important role in the entire solid luminescence. The atoms of rare earth elements have an unfilled and externally shielded 4f-5d electronic configuration, so they have rich electronic energy levels and long-lived excited states, with more than 200,000 energy level transition channels, which can produce a variety of radiation absorption and emission processes, thereby achieving 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 luminescent center ions in scintillators, such as LaBr:Ce, LYSO:Ce, CLYC:Ce, SrI2:Eu, CLYC:Pr, etc. These rare earth doped scintillators show high light yield, excellent energy resolution and good particle discrimination ability. Some of them are currently commercialized. However, these materials also face a variety of problems: europium ions (Eu 2+) doped scintillating crystals can obtain extremely high light yield, excellent energy resolution and fast decay time due to the 5d-4f allowed transition, but the strong self-absorption of its luminescence will seriously deteriorate the scintillator performance of the material as the size of the scintillator is enlarged; cerium ions (Ce 3+ ) doped scintillator crystals, such as LaBr3:Ce, CLYC:Ce, etc., have both high light yield and fast decay, but the free carriers will be captured by defects to emit light, which makes the performance of the crystal have a bottleneck, and the deliquescent nature of the above halide scintillators themselves is difficult to suppress, which makes them face many limitations during use.

[0005] Therefore, the research on low-dimensional structured halide scintillating crystalline materials and their doping with rare earth ions is the frontier direction of the development of scintillating materials in the field of radiation detection. However, there are still many problems in the combination of the two: first, the ionic radius of rare earth ions and the lattice compatibility of low-dimensional halide materials need to be explored. In general, the ionic radius of rare earth ions is large, and it is difficult to enter the lattice of halide materials, or it is easy to cause lattice distortion after entering, resulting in a decrease in the overall stability of the composite material (such as poor air stability and difficulty in single crystal growth); secondly, rare earth ion compounds have a high melting point, while low-dimensional halide materials have a low melting point, so it is necessary to find a suitable crystal growth process; in addition, the concentration segregation problem caused by the introduction of rare earth ions into the matrix of low-dimensional halide scintillating crystal materials during the preparation process and the difficulty in large-scale growth also need further research and exploration. Summary of the invention

[0006] In view of the above technical problems, the purpose of the present invention is to provide a rare earth ion doped enhanced ionizing radiation luminescence low-dimensional halide scintillator and its preparation method and application. The present invention combines the strong confinement effect of low-dimensional halides with the efficient luminescence of rare earth ions to prepare a scintillating material with high ionizing radiation luminescence intensity, good radiation stability and air stability under X-ray excitation, providing a suitable scintillating material for low-cost, high-resolution X-ray detection technology.

[0007] In a first aspect, the present invention provides a rare earth ion doped ionizing radiation luminescence low-dimensional halide scintillator, wherein the chemical formula of the rare earth ion doped ionizing radiation luminescence low-dimensional halide scintillator is 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, RE is Eu 2+ , Yb 2+ 、Ce 3+ , Pr 3+ Sc 3+ , Y3+ ,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 RE rare earth ions, 0<m<10.

[0008] Preferably, 0.05≤m≤2.

[0009] In a second aspect, the present invention provides a method for preparing the above-mentioned rare earth ion doping enhanced ionizing radiation luminescence low-dimensional halide scintillator, the preparation method comprising the following steps: (1) weighing halide raw materials according to the molar ratio of elements in the chemical formula of the rare earth ion doped enhanced ionizing radiation luminescence low-dimensional halide scintillator, placing them in a crucible and vacuum welding them, and heating them for the first time to the melting temperature of the raw materials with the highest melting point for pre-synthesis to obtain a pre-synthesized material; (2) placing the crucible containing the pre-synthesized material in a crystal growth furnace and heating it for a second time to the melting temperature of the highest melting point raw material, and maintaining the temperature of the bottom of the capillary structure of the crucible near the crystallization point temperature of the pre-synthesized material; (3) The crucible is lowered and rotated in a crystal growth furnace to grow crystals. After the growth is completed, annealing and cooling are performed to obtain the rare earth ion doped enhanced ionizing radiation luminescence low-dimensional halide scintillator.

[0010] 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 insulation time is 4-8 hours.

[0011] Preferably, in step (2), the vacuum degree of the crystal growth furnace is ≤10 -3 Pa.

[0012] Preferably, in step (2), the temperature of the bottom of the capillary structure of the crucible is 280-600°C.

[0013] Preferably, in step (3), the growth temperature gradient of the crystal growth furnace is 5 to 50°C / cm.

[0014] Preferably, in step (3), the crucible rotates at a speed greater than 0 and less than or equal to 200 r / min.

[0015] Preferably, in step (3), the crucible descends at a speed of 0.01 to 10.0 mm / h.

[0016] In a third aspect, the present invention provides an application of the above-mentioned rare earth ion doped enhanced ionizing radiation luminescent halide scintillator in X-ray imaging, gamma ray detection and particle detection.

[0017] Beneficial Effects (1) The present invention converts Eu 2+ Plasma is doped into Cs5Cu3Cl6I2 and other matrices, and by optimizing the ion doping concentration, a significant increase in the light output of the intrinsic material of the undoped matrix is ​​achieved, with the optimal light output approaching 70,000 ph. / MeV. The successful introduction of europium ions and other ions gives the crystal material a faster characteristic decay time of europium and other doped ions. The imaging line pair number of the scintillator crystal under X-rays can reach 18 lp / mm, with excellent X-ray imaging performance; (2) The rare earth ion-doped halide scintillator of the present invention has the advantages of non-deliquescent, high ionizing radiation luminous efficiency, high light output, high spatial resolution, etc. It can be used to detect X-rays, gamma rays and other rays or particle detection, and has important application prospects in the fields of medical imaging, security inspection, oil well exploration and industrial inspection. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The photos of the halide scintillator samples provided in Examples 1-6, 12 and Comparative Examples 1-5 under natural light; Figure 2 This is a photo of the halide scintillator sample provided in Example 7 under natural light; Figure 3 The photos of the halide scintillator samples prepared in Examples 8-11 under natural light; Figure 4 The fluorescence emission spectra of the scintillator single crystals prepared in Examples 1 and 5; Figure 5 1 is the fluorescence attenuation graph of the halide scintillator samples prepared in Examples 1 and 5; Figure 6 is the X-ray imaging resolution diagram of the scintillation single crystal prepared in Examples 1 and 5; Figure 7 A comparison chart of the ionizing radiation luminescence intensity of the scintillation single crystals synthesized in Examples 1-6 and the BGO scintillation single crystal sample provided in Comparative Example 1; Figure 8 This is a comparison chart of the ionizing radiation luminescence intensity of the scintillator samples prepared in Example 5 and Comparative Example 2; Fig. 9 This is a comparison chart of the ionizing radiation luminescence intensity of the scintillation single crystal samples prepared in Example 5 and Comparative Example 5; Fig.10 1 is a comparison diagram of ionizing radiation luminescence peak types of the halide scintillator samples prepared in Examples 1 and 7; Fig.11 1 is a comparison diagram of ionizing radiation luminescence peak types of the halide scintillator samples prepared in Examples 8 and 9; Fig.12 10 and 11 are comparison diagrams of ionizing radiation luminescence peak types of the halide scintillator samples prepared in Examples 10 and 11; Fig.13 XRD diagram of the scintillating single crystal samples synthesized in Examples 1 and 5; Fig.14 This is a surface comparison diagram of the halide scintillation crystal synthesized in Example 5 and Comparative Example 5 under a polarizing microscope; Fig.15 This is the ionizing radiation luminescence spectrum of the halide scintillator sample prepared in Example 12. DETAILED DESCRIPTION

[0019] The present invention is further described below by the following embodiments. It should be understood that the following embodiments are only used to illustrate the present invention, but not to limit the present invention.

[0020] First, the present invention provides a rare earth ion doped low-dimensional halide scintillator for enhancing ionizing radiation luminescence. The chemical formula of the rare earth ion doped low-dimensional halide scintillator for enhancing ionizing radiation luminescence can be A5B3(Cl x Br y I 1-x-y )8: m at% RE; wherein: A = at least one of Rb, K, Na, Cs, B = at least one of Cu, Ag, Au, 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, preferably, 0.05≤m≤2. It should be noted that x and y can be any real number within the specified range.

[0021] 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 proportions to optimize the performance of halide scintillators: by artificially introducing aisovalent rare earth ions in the lattice, introducing new luminescence centers or defect energy levels, the carriers in the raw materials are more effectively utilized, the proportion of non-radiative transitions is reduced, and efficient luminescence is achieved; at the same time, by regulating the rare earth ion doping concentration, 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 guaranteed, the performance degradation 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 effect, etc., and ultimately lead to degradation of material performance or even failure to grow single crystals.

[0022] In addition, the halogen anion Cl used in the present invention - Br - ,I - The ionic radius increases in order (Cl - <Br - - ). The selection and replacement of different halogen anion types will change the lattice constant of the scintillator material, thereby affecting the material's energy band structure and the coordination environment of the luminescent ions. - The smaller ionic radius of I allows for a more compact coordination structure, resulting in a smaller scintillator crystal field splitting energy (low-energy transition, red shift). - The larger ionic radius of Cu + The plasma enters a coordination structure with higher symmetry, increasing the crystal field splitting energy (high-energy transition, blue shift). The present invention can optimize the luminescence wavelength of the material and achieve regulation of different luminescence bands by adjusting the solid solution ratio of the raw material halogen anion; at the same time, due to the change of ion radius and electronegativity, the spin-orbit coupling effect of the material can be regulated to optimize the radiation 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.

[0023] ​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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] In summary, the present invention artificially introduces aliovalent rare earth ions into the low-dimensional halide lattice to form new defective luminescence centers, and through the competition between rare earth ion luminescence and intrinsic luminescence, or the formation of rare earth ion bound exciton luminescence, or the existence of an energy transfer effect between the two luminescence centers, etc., the properties of the scintillator such as light yield and decay time 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 achieved.

[0030] The following is an exemplary description of the method for preparing the rare earth ion doped enhanced ionizing radiation luminescence low-dimensional halide scintillator provided by the present invention. The preparation method may include the following steps: (1) weighing halide raw materials according to the molar ratio of elements in the chemical formula of the rare earth ion doped enhanced ionizing radiation luminescence low-dimensional halide scintillator, placing them in a crucible and vacuum welding and sealing them, heating them to the melting temperature of the raw materials with the highest melting point for the first time under a vacuum environment and mixing them evenly to perform pre-synthesis, and cooling the molten liquid after it becomes a uniform clear liquid to obtain a pre-synthesized material; (2) placing the crucible containing the pre-synthesized material vertically in a high vacuum crystal growth furnace, heating the pre-synthesized material in the crucible for a second time to the melting temperature of the raw material with the highest melting point, and adjusting 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; (3) The crucible is adjusted to a suitable temperature gradient in a crystal growth furnace, and is simultaneously rotated downward to grow crystals. After annealing and cooling, the rare earth ion-doped enhanced ionizing radiation luminescence low-dimensional halide scintillator is obtained.

[0031] In some embodiments, in step (1), the halide raw material may include CsCl, CsBr, CuCl, CuI, CeI3, EuI2, PrI3, YbI2; preferably, the purity of the halide raw material may be ≥99.99 wt%.

[0032] In some embodiments, in step (1), the pre-synthesis temperature may be 550-800°C, and the holding time may be 4-8 hours; preferably, the pre-synthesis vacuum degree may be 1×10 -4 ~1×10 -3 Pa. If the temperature is too low, the raw material melting point cannot be reached; if the temperature is too high, the halide raw material is easy to volatilize and decompose.

[0033] In some embodiments, in step (2), the vacuum degree of the high vacuum crystal growth furnace may be ≤10 -3 Pa.

[0034] In some embodiments, in step (2), the temperature of the bottom of the capillary structure of the crucible may be ±10°C of the crystallization point of the pre-synthesized material, preferably 280-600°C.

[0035] It should be noted that in step (2), the position of the crucible and the temperature in the furnace can be finely adjusted with the assistance of an observation window and a temperature measuring thermocouple 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. In this process, some crystals should begin to form at the bottom of the capillary structure. 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.

[0036] In addition, in the preparation method disclosed in the present invention, the first heating can make the raw materials fully melt and mix to obtain a polycrystalline target product; the second heating can make the raw materials mixed for the second time, and the two melting and mixing help to improve the quality of the final crystal growth, reduce the formation of defects, and ensure the uniformity of the crystal components.

[0037] In some embodiments, in step (3), the growth temperature gradient of the crystal growth furnace may be 5-50°C / cm. A temperature gradient that is too large may easily cause thermal stress accumulation and cause crystal cracking; a temperature gradient that is too small may weaken the driving force for crystal growth and affect the quality of the crystal.

[0038] In some embodiments, in step (3), the rotation rate of the crucible may be >0 and ≤200 r / min.

[0039] Among them, slowly rotating and descending the crucible in the crystal growth furnace can promote the molecular movement in the melt through the centrifugal force of rotation, reduce the radial temperature gradient of the melt, reduce the local supercooling or overheating caused by uneven temperature gradient, and is beneficial to the stability of the solid-liquid interface. At the same time, it helps to evenly disperse the dopant in the melt and effectively inhibit the segregation phenomenon of the dopant in the melt to grow high-quality single crystals. It should be noted that a suitable rotation rate should be selected during crystal growth. Too large or too small a rotation rate will affect the quality of the crystal. Too large a rotation rate will easily cause excessive disturbance of the melt and interface instability; too small a rotation rate will limit the diffusion of the solute and fail to inhibit segregation.

[0040] In some embodiments, in step (3), the descent rate of the crucible can be 0.01 to 10.0 mm / h. In this way, it can be ensured 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 the descent rate of the crucible can be dynamically adjusted in real time according to the observed interface morphology. By real-time monitoring of the crystallization during the crystal descent process and dynamically adjusting the furnace temperature field, a suitable temperature gradient can be maintained to ensure the integrity and transparency of the crystal growth.

[0041] In some embodiments, in step (3), the annealing cooling rate can be 0.1-50°C / h. After the crystal growth is completed, the annealing cooling method can release the stress inside the crystal to the maximum extent to avoid cracking of the crystal in subsequent processing.

[0042] In summary, the present invention adopts the simple-to-operate Bridgman descent method to efficiently grow transparent, inclusion-free, 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.

[0043] The rare earth ion doped enhanced ionizing radiation luminescent halide scintillator obtained by the preparation method provided by the present invention can be used in X-ray imaging, gamma ray detection and particle detection, including medical imaging, security inspection, oil well exploration and industrial detection. When used in high-resolution X-ray imaging, the imaging line logarithm of the crystal under X-ray can be provided.

[0044] The following further examples are given 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 scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention all belong to the scope of protection of the present invention. The specific process parameters of the following examples are also only examples within a suitable range, that is, those skilled in the art can make selections within a suitable range through the description of this article, and are not limited to the specific values ​​​​exemplified below. If not specifically stated, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0045] Unless otherwise specified, in the present invention: (1) Using a tungsten target X-ray tube as the excitation source and an Ocean Optics QEpro spectrometer as the detector, the ionizing radiation luminescence performance of the rare earth ion doped halide scintillator was tested; (2) The photoexcitation and emission spectra of the rare earth ion doped halide scintillator enhanced by ionizing radiation luminescence were measured using a Horiba Jobin Yvon Fluorolog-3 fluorescence spectrometer as the excitation source and detector; (3) The X-ray diffraction spectrum of the rare earth ion doped enhanced ionizing radiation luminescence halide scintillator was measured using a Bruker D8 high-resolution powder X-ray diffractometer.

[0046] Example 1 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 comprises the following steps: (1) Weigh the halide raw materials according to the molar ratio of the elements 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 of about 2 cm long. Evacuate the crucible to a vacuum degree of 10 -4Pa and weld seal; move the welded quartz crucible to a crucible stand and let it stand; during this period, use an electric spark gun vacuum detector to test the contact of the crucible, and the appearance of glow discharge indicates that the inside of the crucible is a vacuum environment, and the crucible is welded successfully; transfer the welded crucible to a tubular furnace for material presynthesis, heat it to 600°C in a vacuum environment, melt the mixed raw materials, and rotate them after melting to mix the raw materials uniformly, and keep this state for 5 hours. During this period, the presynthesis is completed after the molten liquid is observed to be a uniform clear liquid, and the temperature is slowly lowered with the furnace to obtain a presynthesized material; (2) Place the crucible containing the pre-synthesized material vertically in a high vacuum crystal transparent growth furnace and adjust it to a suitable position; control the vacuum degree in the furnace to ≤10 -3 Pa, the pre-synthesized material is heated for the second time, and the temperature in the furnace is raised from room temperature to 600°C after 8 hours, so that the pre-synthesized material is melted for the second time. With the assistance of the observation window and the temperature measuring thermocouple, the position of the crucible and the temperature field in the furnace are 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. In this process, some crystals should begin to form at the bottom of the capillary structure; (3) The crucible is slowly rotated and lowered in the crystal growth furnace, and the speed is set to 30 r / min. During the growth process, a high-resolution CCD camera is used to closely observe the morphology of the interface between the crystal and the melt. According to the observed interface morphology, the descent rate of the crucible is dynamically adjusted in real time. The initial descent 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, the crystallization of the crystal during its descent is monitored in real time, and the furnace temperature field is dynamically adjusted to maintain a suitable temperature gradient to ensure the integrity and transparency of the crystal growth. After the crystal growth is completed, the annealing cooling method is used to release the stress inside the crystal to the maximum extent to avoid cracking of the crystal during the growth process and subsequent treatment. The cooling rate is set to 5°C / h. After cooling treatment, a single crystal of low-dimensional halide scintillator Cs5Cu3Cl6I2 is obtained.

[0047] After testing, the Cs5Cu3Cl6I2 halide scintillator obtained in Example 1 has good crystallinity and radiation stability, no deliquesce, no self-absorption effect, and its uniform melting property has obvious advantages for large-sized crystal growth. The light yield evaluated under steady-state X-ray is 49,000 photons / MeV.

[0048] Example 2 The rare earth ion doping enhanced ionizing radiation luminescence low-dimensional halide scintillator Cs5Cu3Cl6I2:0.1%Eu provided in this embodiment 2+ (A=Cs, B=Cu, x=0.75, y=0, m=0.1, RE=Eu 2+ ) is prepared by referring to Example 1, the main difference being that: In step (1), according to Cs5Cu3Cl6I2:0.1% Eu 2+ Weigh the halide raw materials according to the molar ratio of elements in the mixture.

[0049] After testing, the Cs5Cu3Cl6I2:0.1% Eu obtained in Example 2 2+ Halide scintillators have good crystallinity and radiation stability, are non-deliquescent, have low self-absorption effects, and their consistent melting characteristics have obvious advantages for large-sized crystal growth. The light yield evaluated under steady-state X-rays is 60,000 photons / MeV, which is 22% higher than that of undoped crystals.

[0050] Example 3 The rare earth ion doping enhanced ionizing radiation luminescence low-dimensional halide scintillator Cs5Cu3Cl6I2:0.2% Eu 2+ (A=Cs, B=Cu, x=0.75, y=0, m=0.2, RE=Eu 2+ ) is prepared by referring to Example 1, the main difference being that: In step (1), according to Cs5Cu3Cl6I2:0.2% Eu 2+ Weigh the halide raw materials according to the molar ratio of elements in the mixture.

[0051] After testing, the Cs5Cu3Cl6I2 obtained in Example 3: 0.2% Eu 2+ Halide scintillators have good crystallinity and radiation stability, are non-deliquescent, have low self-absorption effects, and their consistent melting characteristics have obvious advantages for large-sized crystal growth. The light yield evaluated under steady-state X-rays is 62,000 photons / MeV, which is 26% higher than that of undoped crystals.

[0052] Example 4 The rare earth ion doping enhanced ionizing radiation luminescence low-dimensional halide scintillator Cs5Cu3Cl6I2:0.5% Eu 2+ (A=Cs, B=Cu, x=0.75, y=0, m=0.5, RE=Eu 2+ ) is prepared by referring to Example 1, the main difference being that: In step (1), according to Cs5Cu3Cl6I2:0.5% Eu 2+ Weigh the halide raw materials according to the molar ratio of elements in the mixture.

[0053] After testing, the Cs5Cu3Cl6I2:0.5% Eu obtained in Example 4 2+Halide scintillators have good crystallinity and radiation stability, are non-deliquescent, have low self-absorption effects, and their consistent melting characteristics have obvious advantages for large-sized crystal growth. The light yield evaluated under steady-state X-rays is 67,000 photons / MeV, which is 36% higher than that of undoped crystals.

[0054] Example 5 The rare earth ion doping enhanced ionizing radiation luminescence low-dimensional halide scintillator Cs5Cu3Cl6I2:1.0% Eu 2+ (A=Cs, B=Cu, x=0.75, y=0, m=1.0, RE=Eu 2+ ) is prepared by referring to Example 1, the main difference being that: In step (1), according to Cs5Cu3Cl6I2:1.0% Eu 2+ Weigh the halide raw materials according to the molar ratio of elements in the mixture.

[0055] After testing, the Cs5Cu3Cl6I2 obtained in Example 5: 1.0% Eu 2+ Halide scintillators have good crystallinity and radiation stability, are non-deliquescent, have low self-absorption effects, and their consistent melting characteristics have obvious advantages for large-sized crystal growth. The light yield evaluated under steady-state X-rays is 69,700 photons / MeV, which is 42% higher than that of undoped crystals.

[0056] Example 6 The rare earth ion doping enhanced ionizing radiation luminescence low-dimensional halide scintillator Cs5Cu3Cl6I2:2.0% Eu 2+ (A=Cs, B=Cu, x=0.75, y=0, m=2.0, RE=Eu 2+ ) is prepared by referring to Example 1, the main difference being that: In step (1), according to Cs5Cu3Cl6I2:2.0% Eu 2+ Weigh the halide raw materials according to the molar ratio of elements in the mixture.

[0057] After testing, the Cs5Cu3Cl6I2 obtained in Example 6: 2.0% Eu 2+ Halide scintillators have good crystallinity and radiation stability, are non-deliquescent, have low self-absorption effects, and their consistent melting characteristics have obvious advantages for large-sized crystal growth. Due to the concentration quenching effect, the light yield under steady-state X-rays is evaluated to be 52,000 photons / MeV, which is 6% higher than that of undoped crystals.

[0058] Example 7 The rare earth ion doping enhanced ionizing radiation luminescence low-dimensional halide scintillator Cs5Cu3Cl6I2:1.0% Pr 3+ 、Cs5Cu3Cl6I2:1.0% Ce 3+ 、Cs5Cu3Cl6I2:1.0% Yb 2+ (A=Cs, B=Cu, x=0.75, y=0, m=1.0, RE=Pr 3+ 、Ce 3+ , Yb 2+ The preparation method of one of the above) is as described in Example 1, with the main difference being that: In step (1), Cs5Cu3Cl6I2:1.0% Pr 3+ 、Cs5Cu3Cl6I2:1.0% Ce 3+ 、Cs5Cu3Cl6I2:1.0% Yb 2+ Weigh the halide raw materials according to the molar ratio of elements in the mixture.

[0059] After testing, the Cs5Cu3Cl6I2:1.0% Pr obtained in Example 7 3+ 、Cs5Cu3Cl6I2:1.0% Ce 3+ 、Cs5Cu3Cl6I2:1.0% Yb 2+ Halide scintillators have efficient ionizing radiation luminescence performance and can be used in X-ray imaging, gamma-ray detection and other fields.

[0060] Example 8 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 embodiment refers to that in Example 1, the main difference is that: In step (1), the halide raw material is weighed according to the molar ratio of the elements in Cs5Cu3Cl6Br2.

[0061] After testing, the Cs5Cu3Cl6Br2 halide scintillation crystal obtained in Example 8 has a strong radioluminescence response, and the ionizing radiation luminescence spectrum shows that it has efficient ionizing radiation luminescence performance, with the luminescence peak at 480 nm.

[0062] Example 9 The rare earth ion doping enhanced ionizing 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+ ) is prepared by referring to Example 1, the main difference being that: In step (1), according to Cs5Cu3Cl6Br2:1.0% Eu 2+ Weigh the halide raw materials according to the molar ratio of elements in the mixture.

[0063] After testing, the Cs5Cu3Cl6Br2 obtained in Example 9: 1.0% Eu 2+ There are two luminescence centers in halide scintillation crystals. Eu appears on the basis of the original luminescence. 2+ Characteristic luminescence, the luminescence peak is located at 450 nm, and the peak intensity is higher than the original luminescence peak at 480nm. The ionizing radiation luminescence spectrum shows that it has efficient ionizing radiation luminescence performance.

[0064] Example 10 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 embodiment refers to that in Example 1, the main difference is that: In step (1), the halide raw material is weighed according to the molar ratio of the elements in Cs5Cu3Cl6BrI.

[0065] After testing, the Cs5Cu3Cl6BrI halide scintillation crystal obtained in Example 10 has a strong radioluminescence response, and the ionizing radiation luminescence spectrum shows that it has efficient ionizing radiation luminescence performance, with the luminescence peak at 520 nm.

[0066] Embodiment 11 The rare earth ion doping enhanced ionizing radiation luminescence low-dimensional halide scintillator Cs5Cu3Cl6BrI:1.0% Eu 2+ (A=Cs, B=Cu, x=0.75, y=0.125, m=1.0, RE=Eu 2+ ) is prepared by referring to Example 1, the main difference being that: In step (1), according to Cs5Cu3Cl6BrI:1.0% Eu 2+ Weigh the halide raw materials according to the molar ratio of elements in the mixture.

[0067] After testing, the Cs5Cu3Cl6BrI obtained in Example 11: 1.0% Eu 2+ There are two luminescence centers in halide scintillators. Eu appears on the basis of the original luminescence. 2+ Characteristic luminescence, the luminescence peak is at 470 nm, the original luminescence peak is at 520 nm, and the ionizing radiation luminescence spectrum shows that it has efficient ionizing radiation luminescence performance.

[0068] Example 12 The rare earth ion doping enhanced ionizing radiation luminescence low-dimensional halide scintillator Cs5Cu3Cl7I1:1.0%Eu provided in this embodiment 2+ (A=Cs, B=Cu, x=0.875, y=0, m=1.0, RE=Eu 2+ ) is prepared by referring to Example 1, the main difference being that: In step (1), according to Cs5Cu3Cl7I1:1.0%Eu 2+ Weigh the halide raw materials according to the molar ratio of elements in the mixture.

[0069] After testing, the Cs5Cu3Cl7I1:1.0%Eu obtained in Example 12 2+ The halide scintillator has two luminescence centers, with luminescence peaks at 470 nm and 523 nm respectively. It appears as cold white light under ultraviolet light, and the ionizing radiation luminescence spectrum shows that it has efficient ionizing radiation luminescence performance.

[0070] Comparative Example 1 This comparative example provides a standard scintillator in the form of a bulk single crystal. The chemical formula of the scintillator is Bi4Ge3O 12 , as a comparison standard for X-ray steady-state light yield, the default light yield is 8,000photons / MeV.

[0071] Comparative Example 2 The scintillator provided in this comparative example is Cs5Cu3Cl6I2:10.0%Eu 2+ (A=Cs, B=Cu, x=0.75, y=0, m=10.0, RE=Eu 2+ ) is prepared by referring to Example 1, the main difference being that: In step (1), according to Cs5Cu3Cl6I2:10.0%Eu 2+ Weigh the halide raw materials according to the molar ratio of elements in the mixture.

[0072] After testing, the quality of the scintillator single crystal obtained in Comparative Example 2 is poor, and due to the high concentration of europium ion doping, the concentration quenching effect causes the light yield to decrease. The light yield is estimated to be 30,000 photons / MeV, and the scintillation performance is seriously deteriorated.

[0073] Comparative Example 3 The scintillator provided in this comparative example is Cs5Cu3Cl1I7:1.0%Eu 2+ (A=Cs, B=Cu, x=0.125, y=0, m=1.0, RE=Eu 2+ ) is prepared by referring to Example 1, the main difference being that: In step (1), according to Cs5Cu3Cl1I7:1.0%Eu2+ Weigh the halide raw materials according to the molar ratio of elements in the mixture.

[0074] After testing, it was found that due to the imbalance of the chlorine-iodine ratio in this comparative example, the crystallinity of the scintillator material finally prepared was poor, and no high-quality single crystal was prepared by the Bridgman method.

[0075] Comparative Example 4 The scintillator provided in this comparative example is Cs5Cu3Cl8:1.0%Eu 2+ (A=Cs, B=Cu, x=1, y=0, m=1.0, RE=Eu 2+ ) is prepared by referring to Example 1, the main difference being that: In step (1), according to Cs5Cu3Cl8:1.0%Eu 2+ Weigh the halide raw materials according to the molar ratio of elements in the mixture.

[0076] After testing, it was found that after all the halogen atoms were replaced with chlorine, the material had a certain degree of crystallinity, and high-quality single crystals could be prepared by the Bridgman method. However, the material underwent a phase change during the cooling process, resulting in crystal pulverization and serious degradation of the scintillation performance, making it impossible to evaluate its light yield. The powder XRD results showed that its matrix component was biased towards Cs3Cu2Cl5.

[0077] Comparative Example 5 The scintillator provided in this comparative example is Cs5Cu3Cl6I2:1.0% Eu 2+ The preparation method comprises the following steps: According to Cs5Cu3Cl6I2:1.0% Eu 2+ Weigh the halide raw materials according to the molar ratio of the elements in the glove box, mix the raw materials evenly and transfer them to a quartz crucible with a capillary of about 2 cm in length in an argon or nitrogen glove box, evacuate the crucible and seal it with welding; (2) Place the welded quartz crucible vertically in the center of the crystal growth furnace; heat the crystal growth furnace from room temperature to 600°C over 8 hours, keep the temperature for 24 hours to completely melt the raw materials and mix them evenly, adjust the height of the crucible and the furnace temperature, and reduce the temperature of the crucible capillary tip to 310°C; (3) The quartz crucible is lowered relative to the furnace at a speed of 0.5 mm / h. The crystal nucleates at the capillary tip of the crucible and gradually solidifies toward the tail end during the descent until the melt is completely crystallized. Then, the scintillator Cs5Cu3Cl6I2:1.0% Eu is obtained at a rate of 5°C / h. 2+ .

[0078] After testing, the crystal material prepared in Comparative Example 5 contained more inclusions, had poor transparency, and had a large difference in luminescence between the front and rear ends of the crystal. The light yield at the middle position was evaluated to be 50,000 photons / MeV.

[0079] Table 1 below shows the relative light yield data of the halide scintillators prepared in Examples 1-6 and Comparative Examples 1, 2, and 5:

[0080] Figure 1 The photos of the halide scintillator samples provided in Examples 1-6, 12, and Comparative Examples 1-5 under natural light are shown. It can be seen from the figure that when the rare earth doping ion is within a certain concentration range, the grown single crystal sample has a high optical quality, but when the doping concentration is high, it is difficult to grow a high-quality crystal; when the halogen anion ratio is within a certain range, high-quality single crystals can be grown, but if it exceeds the range, it will cause large lattice distortion and it is difficult to grow a high-quality single crystal.

[0081] Figure 2 This is a photo of the halide scintillator sample under natural light provided in Example 7. It can be seen from the figure that the sample material prepared in Example 7 has good crystallinity and transparency, and the crystal as a whole has good optical quality.

[0082] Figure 3 The photos of the halide scintillator samples prepared in Examples 8 to 11 under natural light show that the sample materials prepared in Examples 8 to 11 have good crystallinity and transparency, and have good overall optical quality.

[0083] Figure 4 The fluorescence emission spectra of the scintillator single crystals prepared in Examples 1 and 5 are shown in the figure. 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, with an emission peak at 470 nm; the emission spectrum of the scintillator single crystal prepared in Example 5 under 370 nm excitation is a narrow-spectrum emission of europium ions, and there is no obvious shift in the emission peak position.

[0084] Figure 5 The fluorescence decay diagrams of the halide scintillator samples prepared in Examples 1 and 5. As can be seen from the diagrams, the scintillator single crystal synthesized 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.

[0085] Figure 6 The X-ray imaging resolution diagram of the scintillation single crystal prepared in Examples 1 and 5. It can be seen from the figure that the scintillation single crystal prepared in Example 5 has a relatively high imaging resolution, which can reach 18 lp / mm.

[0086] By exciting the scintillator samples prepared in Examples 1-6 and the BGO crystal in Comparative Example 1 with X-ray ionizing radiation, and collecting spectral data using a fluorescence spectrometer for comparison, the results of Cs5Cu3Cl6I2: Eu3O2 with different europium doping amounts were obtained. 2+ Comparison of luminous intensity of ionizing radiation from scintillators. Figure 7 The ionizing radiation luminescence intensity comparison diagram 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 the luminescence efficiency of Example 5 when the europium doping amount is 1.0% is relatively the best, and its relative light yield is calculated to reach 69,700 photons / MeV, which is 42% higher than that of Example 1.

[0087] Figure 8 The ionizing radiation luminescence intensity comparison diagram 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 ionizing radiation luminescence performance of the scintillator, and the emission peak position has no obvious change. The light yield of Comparative Example 2 is evaluated to be 30,000 photons / MeV.

[0088] Fig. 9 The figure is a comparison of the ionizing radiation luminescence intensity of the scintillation single crystal samples prepared in Example 5 and Comparative Example 5. It can be seen from the figure that the ionizing radiation luminescence intensity of the single crystal sample prepared by the rotary descent in the vacuum transparent furnace is higher than that of the sample prepared by the traditional descent process, and the emission peak position does not change significantly.

[0089] Fig.10 The ionizing radiation luminescence peak type comparison diagram of the halide scintillator samples prepared in Examples 1 and 7. It can be seen from the figure that Cs5Cu3Cl6I2:1.0% Pr 3+ With Cs5Cu3Cl6I2:1.0% Ce 3+ The emission peak is at 480 nm, and the peak shapes of the two are similar. Cs5Cu3Cl6I2:1.0% Yb 2+ The luminescence peak is located at 472 nm, which is overall blue-shifted. All three have efficient ionizing radiation luminescence performance.

[0090] Fig.11 The figure is a comparison diagram of the ionizing radiation luminescence peaks 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 intrinsic self-trapped exciton luminescence, and the luminescence peaks are located at 450 nm and 480 nm, respectively.

[0091] Fig.12The figure is a comparison diagram of the ionizing radiation luminescence peaks 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 intrinsic self-trapped exciton luminescence, and the luminescence peaks are located at 470 nm and 520 nm, respectively.

[0092] Fig.13 1 and 2 are XRD patterns of the scintillating single crystal samples synthesized in Examples 1 and 5. As can be seen from the figure, the samples synthesized in Example 1 and Example 5 are of the same phase.

[0093] Fig.14 This is a surface comparison of the halide scintillator crystals synthesized in Example 5 and Comparative Example 5 under a polarizing 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 the overall transparency is relatively high (the scratches are caused by the polishing process), while the surface of the single crystal prepared by the growth method of Comparative Example 5 has more holes, inclusions inside, poor overall transparency, and the presence of a second phase.

[0094] Fig.15 This is the ionizing radiation luminescence spectrum of the halide scintillator sample prepared in Example 12. As can be seen from the figure, it has two luminescence centers: characteristic luminescence of europium ions and intrinsic self-trapped exciton luminescence, with luminescence peaks at 470 nm and 523 nm, respectively.

[0095] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.

Claims

1. A rare earth ion doped low-dimensional halide scintillator with enhanced ionizing radiation luminescence, characterized in that: The chemical formula of the rare earth ion doped enhanced ionizing radiation luminescence low-dimensional halide scintillator is 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, 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 the 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 ionizing radiation luminescence low-dimensional halide scintillator according to claim 1, characterized in that: 0.05≤m≤2。 3. A method for preparing the rare earth ion doped enhanced ionizing radiation luminescence low-dimensional halide scintillator according to claim 1, characterized in that: The preparation method comprises the following steps: (1) Weighing halide raw materials according to the molar ratio of elements in the chemical formula of the rare earth ion doped enhanced ionizing radiation luminescence low-dimensional halide scintillator according to claim 1, placing them in a crucible and vacuum welding sealing, heating them for the first time to the melting temperature of the raw materials with the highest melting point for pre-synthesis, and obtaining a pre-synthesized material; (2) placing the crucible containing the pre-synthesized material in a crystal growth furnace and heating it for a second time to the melting temperature of the highest melting point raw material, and maintaining the temperature of the bottom of the capillary structure of the crucible near the crystallization point temperature of the pre-synthesized material; (3) The crucible is lowered and rotated in a crystal growth furnace to grow crystals. After the growth is completed, annealing and cooling are performed to obtain the rare earth ion doped enhanced ionizing radiation luminescence 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 pre-synthesis temperature is 550-800°C, and the insulation 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 is ≤10 -3 Pa.

6. The preparation method according to claim 3, characterized in that: In step (2), the temperature of 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 to 50°C / cm.

8. The preparation method according to claim 3, characterized in that: In step (3), the crucible rotates at a speed greater than 0 and less than or equal to 200 r / min.

9. The preparation method according to claim 3, characterized in that: In step (3), the crucible descends at a speed of 0.01 to 10.0 mm / h.

10. Use of the rare earth ion doped enhanced ionizing radiation luminescence low-dimensional halide scintillator according to claim 1 in X-ray imaging, gamma ray detection and particle detection.

Images