Highly-oriented quasi-two-dimensional perovskite multi-wafer scintillator for X-ray detection imaging and preparation method of highly-oriented quasi-two-dimensional perovskite multi-wafer scintillator
By fabricating highly oriented quasi-two-dimensional perovskite multi-crystal scintillators, the problem of uneven imaging light output in existing perovskite scintillator materials has been solved, achieving high-resolution X-ray imaging, which is applicable to fields such as medical imaging diagnosis, security inspection and industrial testing.
Patent Information
- Application Number
- CN202511570014.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-30
- Publication Date
- 2026-02-10
AI Technical Summary
Most existing perovskite scintillator materials exist in the form of powder, thin film or nanocrystals. The grain orientation is disordered, and their layered structure is not fully utilized. This results in severe scattering of fluorescence excited by incident X-rays in the vertical direction, uneven imaging light output, and insufficient spatial resolution and imaging clarity.
Highly oriented quasi-two-dimensional perovskite multi-crystal scintillators were prepared by using phenylethyl ammonium bromide, lead cesium tribromide, and ammonium thiocyanate as main raw materials through powder pressing and annealing processes. This process formed a layered crystal structure with highly oriented grains, reducing light scattering.
It achieves highly oriented crystal alignment in large-area thick sheets, reduces light scattering, improves imaging uniformity and spatial resolution, is low in cost and easy to prepare, and is suitable for high-resolution X-ray imaging equipment.
Abstract
Description
Technical Field
[0001] This invention relates to the field of radiation detection and scintillation materials technology, specifically to a highly oriented quasi-two-dimensional perovskite multi-crystal scintillator for X-ray detection imaging and its preparation method. Background Technology
[0002] Scintillators are materials that can convert high-energy X-rays and other ionizing radiation into visible light, and they have wide applications in security inspection, industrial non-destructive testing, medical imaging diagnostics, and scientific research. Currently commonly used X-ray imaging scintillators include inorganic crystal scintillators (such as cesium iodide-doped thallium (CsI:Tl) and lutetium-lutetium yttrium aluminum garnet (LYSO:Ce)) and powder phosphor screens. Traditional crystal scintillators are typically fabricated using crystal growth methods such as the Czochralski method to prepare large-size single crystals, a process that is complex, time-consuming, and costly. Furthermore, the limited size of single crystals makes it difficult to fabricate large-area imaging screens. To reduce costs and obtain large-area scintillators, some solutions involve coating scintillator powder grains onto a substrate to form a phosphor screen. However, in this two-dimensional powder scintillator screen, the grains are randomly oriented, resulting in severe vertical scattering of the fluorescence excited by incident X-rays, leading to uneven imaging light output and reduced spatial resolution and image clarity.
[0003] In recent years, metal halide perovskite materials have been studied for their high luminous efficiency and ease of solution processing, making them suitable for use as scintillator materials in X-ray detection and imaging. In particular, quasi-two-dimensional perovskites, with their naturally layered structure and anisotropic optical properties, are expected to show advantages in reducing self-absorption and improving luminous efficiency.
[0004] However, most existing perovskite scintillators exist in the form of powder, thin film, or nanocrystals, with disordered grain orientation, failing to fully utilize their layered structure to reduce optical scattering. Furthermore, fabricating quasi-two-dimensional perovskite materials into large-area thick films or sheets while maintaining a highly oriented crystal arrangement remains a technical challenge. Therefore, how to provide a perovskite scintillator that is easy to prepare and inexpensive, enabling it to achieve a highly oriented crystal arrangement in large-area thick sheets, thereby reducing vertical light scattering and improving imaging uniformity and spatial resolution, is a technical problem that urgently needs to be solved in this field. Summary of the Invention
[0005] The purpose of this invention is to provide a highly oriented quasi-two-dimensional perovskite multi-crystal scintillator for X-ray detection imaging and its preparation method, so as to solve the problems mentioned in the background art.
[0006] To achieve the above objectives, the present invention provides the following technical solution: a highly oriented quasi-two-dimensional perovskite polycrystalline scintillator for X-ray detection imaging, comprising phenylethyl ammonium bromide, lead tribromide, and ammonium thiocyanate, wherein the molar ratio of phenylethyl ammonium bromide, lead tribromide, and ammonium thiocyanate is 2:4:2, and it contains methylamine thiocyanate additive in an amount of 0 to 1 equivalent relative to the amount of ammonium thiocyanate. The scintillator has a plate-like polycrystalline structure; the perovskite crystals of the polycrystalline scintillator have a quasi-two-dimensional layered crystal structure, and the grains are highly oriented so that their layered crystal planes are parallel to the principal plane of the scintillator sheet.
[0007] Furthermore, the scintillator has a thickness of 0.5–2 mm, a diameter or side length of 5–50 mm, and a mechanical strength of ≥5 MPa, and can be directly used in the assembly of X-ray detection and imaging equipment.
[0008] Furthermore, the scintillator emits green light under X-ray excitation, with an emission peak wavelength of 510–530 nm and a full width at half maximum (FWHM) of ≤50 nm.
[0009] Furthermore, this includes the following steps: Raw material preparation: Weigh out the powders of phenylethyl ammonium bromide, lead tribromide, and ammonium thiocyanate in a molar ratio of 2:4:2, mix them, and grind them thoroughly to obtain a uniform powder mixture. Tableting: The mixed powder is placed in a mold and pressed for 1 to 5 minutes at room temperature under a pressure of 20 to 100 MPa to form a sheet-like blank with a diameter of 10 to 50 mm and a thickness of 0.5 to 2 mm; Inert atmosphere annealing: The sheet-like preform is placed in an inert atmosphere and annealed at 120-180°C for 0.5-2 hours to allow the raw material to undergo a solid-phase reaction and recrystallize, forming a highly oriented quasi-two-dimensional perovskite polycrystalline structure. Cooling: After annealing, the material is cooled to room temperature at a rate of ≤5℃ / min to obtain the highly oriented quasi-two-dimensional perovskite multi-crystal scintillator.
[0010] Furthermore, in the raw material preparation step, methyl thiocyanate (MASCN) in an amount of 0.1 to 1 equivalent relative to the amount of NH4SCN is added as an additive to improve the light yield and stability of the scintillator.
[0011] Furthermore, the inert atmosphere is nitrogen or argon with a purity of ≥99.99%, and the gas flow rate is 50–200 sccm.
[0012] Furthermore, in the tableting step, the mold surface is coated with a release agent, which is polytetrafluoroethylene or silicone oil, to prevent the preform from sticking to the mold.
[0013] Furthermore, in the inert atmosphere annealing step, the annealing temperature is 150±5℃ and the annealing time is 1±0.1 hours to ensure the formation of the optimal layered orientation structure.
[0014] Furthermore, in the cooling step, furnace cooling is adopted at a cooling rate of 2-3℃ / min to reduce internal stress in the crystal.
[0015] This invention provides a highly oriented quasi-two-dimensional perovskite multi-crystal scintillator for X-ray detection imaging and its preparation method, offering the following advantages: Large-area, thick-film scintillator screens can be fabricated using simple powder pressing and annealing processes, eliminating the need for complex and expensive single-crystal growth equipment, resulting in low production costs and easy scaling up of dimensions; the highly oriented layered structure formed within the crystal significantly reduces diffuse scattering of emitted light, improving the brightness uniformity and spatial resolution of X-ray imaging, achieving finer imaging effects; furthermore, the scintillator's material composition and process exhibit good repeatability, resulting in stable imaging screen performance, solving the problems of poor consistency and limited resolution inherent in traditional scintillator screens. Therefore, this scintillator is highly suitable for high-resolution X-ray imaging equipment and is expected to find wide application in fields such as medical imaging diagnostics, security inspection, and industrial detection. Detailed Implementation
[0016] The embodiments of the present invention will be described in further detail below with reference to examples. These examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.
[0017] The present invention provides a method for preparing a highly oriented quasi-two-dimensional perovskite multi-crystal scintillator, comprising the following steps: Raw material preparation: Take phenylethyl ammonium bromide (PEABr), lead cesium tribromide (CsPbBr3) and ammonium thiocyanate (NH4SCN) as raw materials, weigh the powder of each component in a molar ratio of about 2:4:2, and add methyl thiocyanate (MASCN) as an additive with a relative amount of 0 to 1 equivalent of NH4SCN. Place the above powder raw materials in a mortar and grind and mix them thoroughly until a uniform mixture powder is obtained. Tableting: The uniformly mixed perovskite precursor powder is placed in a mold and pressed into a sheet-like blank by applying pressure on a press. The pressure and temperature conditions for tableting are not particularly limited, as long as a dense sheet can be formed. For example, a round or square green sheet with a diameter of about 10 mm and a thickness of about 1 mm can be obtained by pressing at a pressure of tens of megapascals for 2 minutes at room temperature. Inert atmosphere annealing: The sheet-like blank obtained by pressing is transferred to a crucible in a tube furnace or muffle furnace and annealed in an inert atmosphere. The inert gas can be high-purity nitrogen, argon, etc., to prevent the material from being oxidized or decomposed at high temperatures. The annealing temperature and time can be selected according to actual needs. For example, annealing at 150°C in a nitrogen atmosphere for 1 hour. During the annealing process, the raw materials in the sheet-like blank undergo solid-phase reactions and recrystallize to form a quasi-two-dimensional perovskite phase containing PEA organic ammonium. Due to the introduction of PEA cations, the generated perovskite crystals have a layered structure. At the same time, during the slow crystallization process of annealing, each grain spontaneously aligns along the normal direction of the layered crystal plane (perpendicular to the plane of the sheet), thereby gradually forming a highly oriented layered polycrystalline structure. Cooling and Finished Product Acquisition: After annealing and holding, the furnace temperature is lowered to room temperature (slow cooling via furnace cooling can be used), and the sample is removed to obtain a highly oriented quasi-two-dimensional perovskite multi-crystal scintillator product. The resulting sheet is a stable solid crystal flake with a color ranging from light to dark green (depending on thickness and composition), possessing a certain mechanical strength, and can be directly used for assembly in imaging detectors.
[0018] Example 1: Preparation of a scintillator without added MASCN 0.2 mmol of PEABr, 0.4 mmol of CsPbBr3, and 0.2 mmol of NH4SCN were weighed in a molar ratio of 2:4:2 as raw materials. The raw material powders were ground in a mortar for 10 minutes to ensure homogeneity. The mixed powder was poured into a cylindrical mold with a diameter of 10 mm and pressed at approximately 20 MPa for 2 minutes at room temperature to form a circular blank with a diameter of approximately 10 mm and a thickness of approximately 1 mm. The blank was then transferred to a tube furnace filled with nitrogen and annealed at 150°C for 1 hour, followed by furnace cooling to room temperature. Upon removal of the sample, a green, translucent polycrystalline scintillator was observed.
[0019] X-ray diffraction (XRD) tests were performed on the scintillator, revealing significantly increased intensity (00l) family diffraction peaks in its diffraction pattern. This indicates that the perovskite crystals within the sheet have indeed formed a Ruddlesden-Popper layered structure with highly ordered grain orientation, and the normals of the layered crystal planes are mainly perpendicular to the sheet surface. This structural characteristic is consistent with the "highly oriented quasi-two-dimensional" properties expected in this invention. The fabricated scintillator sheet was installed in front of a CCD imaging detector for X-ray imaging tests. The experiment used a standard X-ray resolution chart for imaging, comparing the imaging effects of the scintillator sheet of this invention with those of a conventional commercial powder fluorescent screen. Under the same X-ray dose and scintillator thickness (1 mm), the scintillator sheet of this invention produced a clearer image, capable of clearly distinguishing up to 5 line pairs / mm, while the conventional powder fluorescent screen could only distinguish about 3 line pairs / mm. This result demonstrates that the highly oriented layered scintillator of this invention significantly improves the spatial resolution of X-ray imaging and reduces image blurring. Meanwhile, in multiple repeated imaging experiments, the scintillator of the present invention consistently yielded consistent imaging results, demonstrating excellent stability and repeatability.
[0020] Example 2: Preparation of scintillation sheets with MASCN-assisted crystallization Weigh out 0.2 mmol of PEABr, 0.4 mmol of CsPbBr3, 0.1 mmol of NH4SCN, and 0.1 mmol of MASCN (equivalent to 0.5 equivalents of NH4SCN). Mix and grind the powders evenly in a nitrogen glove box (to avoid the influence of ambient humidity). Then, following the same pressing procedure as in Example 1, press the powder under similar conditions to form a square sheet blank with a size of approximately 10 mm × 10 mm and a thickness of approximately 2 mm. Place the blank in an argon-filled tube furnace and anneal at 130°C for 2 hours, then cool and remove the product. The resulting scintillator sheet appears as a green transparent crystalline flake. XRD analysis shows that the sample also exhibits a quasi-two-dimensional perovskite layered orientation structure, and the intensity of the (00l) diffraction peak is further enhanced compared to Example 1, indicating that the addition of an appropriate amount of MASCN helps to improve the grain orientation and crystal quality. Scanning electron microscopy (SEM) revealed that the internal grain size was larger and the grain boundaries were clearer compared to Example 1, indicating that the addition of MASCN promoted crystal growth and rearrangement. The scintillation sheet was subjected to the same X-ray imaging test as Example 1, yielding clear images with resolution comparable to Example 1. This demonstrates that the addition of MASCN did not weaken the scintillation performance; on the contrary, it improved the crystallinity and stability of the material during preparation. The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments applicable to other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the present invention, shall still fall within the protection scope of the present invention.
Claims
1. A highly oriented quasi-two-dimensional perovskite multi-flake scintillator for X-ray detection imaging, characterized in that, Its components include phenylethyl ammonium bromide, lead tribromide, and ammonium thiocyanate, wherein the molar ratio of phenylethyl ammonium bromide, lead tribromide, and ammonium thiocyanate is 2:4:2, and it contains methylamine thiocyanate additive in an amount of 0 to 1 equivalent relative to the amount of ammonium thiocyanate. The scintillator has a plate-like polycrystalline structure; the perovskite crystals of the polycrystalline sheet have a quasi-two-dimensional layered crystal structure, and the grains are highly oriented so that their layered crystal planes are parallel to the principal plane of the scintillator sheet.
2. The highly oriented quasi-two-dimensional perovskite multi-flake scintillator for X-ray detection imaging according to claim 1, characterized in that, The scintillator has a thickness of 0.5–2 mm, a diameter or side length of 5–50 mm, and a mechanical strength of ≥5 MPa, and is directly used in the assembly of X-ray detection and imaging equipment.
3. A highly oriented quasi-two-dimensional perovskite multi-crystal scintillator for X-ray detection imaging according to claim 2, characterized in that, The scintillator emits green light under X-ray excitation, with an emission peak wavelength of 510–530 nm and a full width at half maximum (FWHM) of ≤50 nm.
4. A method for preparing a highly oriented quasi-two-dimensional perovskite multi-crystal scintillator for X-ray detection imaging as described in claim 3, characterized in that, Includes the following steps: Raw material preparation: Weigh out the powders of phenylethyl ammonium bromide, lead tribromide, and ammonium thiocyanate in a molar ratio of 2:4:2, mix them, and grind them thoroughly to obtain a uniform powder mixture. Tableting: The mixed powder is placed in a mold and pressed for 1 to 5 minutes at room temperature under a pressure of 20 to 100 MPa to form a sheet-like blank with a diameter of 10 to 50 mm and a thickness of 0.5 to 2 mm; Inert atmosphere annealing: The sheet-like preform is placed in an inert atmosphere and annealed at 120-180°C for 0.5-2 hours to allow the raw material to undergo a solid-phase reaction and recrystallize, forming a highly oriented quasi-two-dimensional perovskite polycrystalline structure. Cooling: After annealing, the material is cooled to room temperature at a rate of ≤5℃ / min to obtain the highly oriented quasi-two-dimensional perovskite multi-crystal scintillator.
5. The method for preparing a highly oriented quasi-two-dimensional perovskite multi-crystal scintillator for X-ray detection imaging according to claim 4, characterized in that, In the raw material preparation step, methyl thiocyanate (MASCN) in an amount of 0.1 to 1 equivalent relative to the amount of NH4SCN is added as an additive to improve the light yield and stability of the scintillator.
6. The method for preparing a highly oriented quasi-two-dimensional perovskite multi-crystal scintillator for X-ray detection imaging according to claim 4, characterized in that, The inert atmosphere is nitrogen or argon with a purity of ≥99.99%, and the gas flow rate is 50–200 sccm.
7. The method for preparing a highly oriented quasi-two-dimensional perovskite multi-crystal scintillator for X-ray detection imaging according to claim 4, characterized in that, In the tableting process, the mold surface is coated with a release agent, which is polytetrafluoroethylene or silicone oil, to prevent the preform from sticking to the mold.
8. The method for preparing a highly oriented quasi-two-dimensional perovskite multi-crystal scintillator for X-ray detection imaging according to claim 4, characterized in that, In the inert atmosphere annealing step, the annealing temperature is 150±5℃ and the annealing time is 1±0.1 hours to ensure the formation of the optimal layered orientation structure.
9. The method for preparing a highly oriented quasi-two-dimensional perovskite multi-crystal scintillator for X-ray detection imaging according to claim 4, characterized in that, In the cooling step, furnace cooling is used at a rate of 2-3℃ / min to reduce internal stress in the crystal.