Double-layer crucible, method for preparing perovskite polycrystal material by using double-layer crucible and method for preparing perovskite single crystal

Abstract

The invention provides a double-layer crucible. The double-layer crucible comprises an outer circular tube-shaped container, an inner circular tube-shaped container and a T-shaped cylindrical plug, the double-layer structure can solve the problems of raw material loss and proportion imbalance caused in the process of filling the raw materials into the crucible, and the perovskite crystal which can be used for normal-temperature nuclear radiation detection can be industrially prepared by using the Bridgman method in an economic mode. And a vacuum cavity can be provided as a temperature buffer area, so that the thermal disturbance of a crystal growth interface is reduced. The method can also be used for atmosphere regulation and control, and component segregation caused by element volatilization is relieved. The invention also provides a method for preparing a perovskite polycrystal material and a method for preparing a perovskite single crystal.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of crystal preparation, and particularly relates to a double-layer crucible, a method for preparing perovskite polycrystal material using the same, and a method for preparing perovskite single crystal. BACKGROUND

[0002] With the increasing requirements of radiation detection technology, nuclear radiation detection materials gradually turn to the preparation and research of room-temperature semiconductors.

[0003] Perovskite materials have been proved to have good photoelectric performance and energy spectrum resolution capability, and suitable band gap width enables them to work at room temperature without the need of liquid nitrogen to provide a cooling environment, so they are a very promising room-temperature nuclear radiation detection material. From the preparation route, perovskite materials can be prepared in batches by the Bridgman method, which is also convenient for industrial application.

[0004] Although theoretically, perovskite materials are promising as room-temperature nuclear radiation detection materials, in fact, impurities and impurities in perovskite single crystals prepared by the Bridgman method using the existing industrial Bridgeman crystal preparation equipment will form defect centers to capture carriers, which seriously affects the response of the crystal to the energy of the rays, causing the loss of information of the energy of the rays. The accuracy of the radiation detector made of such perovskite single crystals is difficult to meet the standard.

[0005] In order to realize the industrial applicability of perovskite materials as room-temperature nuclear radiation detection materials, there are still problems to be solved. SUMMARY

[0006] In one aspect, the present application provides a double-layer crucible, which comprises:

[0007] an outer circular tubular container having an opening at the top;

[0008] an inner circular tubular container having an opening at the top, the maximum outer diameter of the inner circular tubular container being smaller than the inner diameter of the opening of the outer circular tubular container, so that the inner circular tubular container can be inserted into the outer circular tubular container through the opening of the outer circular tubular container;

[0009] a T-shaped cylindrical plug having a lower inner insertion section and an upper outer sealing section, the diameter of the lower inner insertion section being smaller than the inner diameter of the opening of the inner circular tubular container, and the diameter of the upper outer sealing section being greater than the inner diameter of the opening of the inner circular tubular container and smaller than the inner diameter of the opening of the outer circular tubular container;

[0010] wherein, when the lower insertion section of the T-shaped cylindrical plug is inserted into the opening of the inner circular tubular container such that the upper outer sealing section of the T-shaped cylindrical plug covers the opening of the inner circular tubular container, and the T-shaped cylindrical plug is inserted into the outer circular tubular container together with the inner circular tubular container from the opening of the outer circular tubular container, the outer circular tubular container has an extended passage portion between the opening thereof and the upper outer sealing section of the T-shaped cylindrical plug.

[0011] Preferably, the outer circular tubular container has a wall thickness of 1.5 to 2 mm, and an outer diameter of the opening thereof ranges from 20 to 21 mm, and the inner circular tubular container has a maximum outer diameter of 16 mm or less.

[0012] Preferably, the inner circular tubular container includes an upper circular tubular portion and a lower conical portion, wherein a bottom circle of the lower conical portion has the same size as a cross section of the upper circular tubular portion, and

[0013] the outer circular tubular container includes an upper circular tubular portion, a middle circular tubular portion, and a lower conical portion, wherein an inner diameter of the middle circular tubular portion is greater than an inner diameter of the upper circular tubular portion, and a bottom circle of the lower conical portion has the same size as a cross section of the middle circular tubular portion.

[0014] Preferably, the inner circular tubular container has a conical angle of the lower conical portion ranging from 30° to 45°;

[0015] the outer circular tubular container has a conical angle of the lower conical portion ranging from 50° to 65°, and is greater than the conical angle of the lower conical portion of the inner circular tubular container by 10° to 25°.

[0016] Preferably, the outer circular tubular container has an inner diameter of the middle circular tubular portion greater than an outer diameter of the upper circular tubular portion of the inner circular tubular container by 4 mm to 10 mm.

[0017] Preferably, the extended passage portion has a length ranging from 120 to 150 mm.

[0018] Preferably, the T-shaped cylindrical plug has the upper outer sealing section having a length ranging from 10 to 15 mm and a diameter of 15 to 16 mm, and the lower insertion section having a length ranging from 10 to 15 mm and a diameter of 11 to 12 mm.

[0019] In another aspect, the present application provides a method of preparing a perovskite polycrystal material using the above-described double-layer crucible, wherein,

[0020] placing reaction raw materials of the perovskite polycrystal material in the inner circular tubular container;

[0021] inserting the lower insertion section of the T-shaped cylindrical plug into the opening of the inner circular tubular container such that the upper outer sealing section of the T-shaped cylindrical plug covers the opening of the inner circular tubular container;

[0022] inserting the T-shaped cylindrical plug together with the inner circular tubular container vertically into the outer circular tubular container;

[0023] connecting the opening of the outer circular tubular container to a vacuum pump;

[0024] vacuumizing using the vacuum pump;

[0025] fusion-sealing the upper outer sealing section of the T-shaped cylindrical plug with the inner wall of the outer circular tubular container; and

[0026] transforming the reaction raw material into the perovskite polycrystal material by heating the outer circular tubular container.

[0027] Preferably, the method further comprises:

[0028] fusion-sealing the lower inner insertion section of the T-shaped cylindrical plug with the inner wall of the inner circular tubular container before or after fusion-sealing the upper outer sealing section of the T-shaped cylindrical plug with the inner wall of the outer circular tubular container after vacuumizing using the vacuum pump.

[0029] Preferably, the method further comprises:

[0030] pre-loading a volatile element compensating material inside the outer circular tubular container.

[0031] In yet another aspect, the present application provides a method for preparing a perovskite single crystal, characterized in that the method comprises:

[0032] performing the above method to obtain a perovskite polycrystal material in the inner circular tubular container,

[0033] performing a Bridgman method on the perovskite polycrystal material in the double-layered crucible to transform the perovskite polycrystal material into a perovskite single crystal. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 A schematic diagram showing one embodiment of the double-layered crucible of the present application is shown.

[0035] Figure 2 An XRD spectrum of the product obtained in Example 1 is shown.

[0036] Figure 3 An X-ray response voltage-current curve of the product obtained in Example 1 is shown.

[0037] Figure 4 An XRD spectrum of the product obtained in Example 2 is shown.

[0038] Figure 5 An X-ray response voltage-current curve of the product obtained in Example 2 is shown.

[0039] Figure 6 An XRD pattern of the product obtained in Comparative Example 1 is shown.

[0040] Figure 7 An X-ray response voltage-current curve of the product obtained in Comparative Example 1 is shown.

[0041] Figure 8 An XRD pattern of the product obtained in Comparative Example 2 is shown.

[0042] Figure 9 An X-ray response voltage-current curve of the product obtained in Comparative Example 2 is shown. DETAILED DESCRIPTION

[0043] In theory, perovskite materials are promising as room-temperature nuclear radiation detection materials, and high-purity crystals prepared by laboratory methods can achieve the corresponding functions, however, in industrial practice, the performance of perovskite single crystals prepared by the Bridgman method using the existing industrial Bridgman crystal preparation device cannot meet the required standards as nuclear radiation detection materials. From the test results, most of the crystals prepared by the Bridgman method have element proportion deviation and unknown impurity phases. Although very precise material proportioning has been taken and impurity elements in the raw materials have been reduced as much as possible, it is still difficult to prepare qualified crystals by the Bridgman method using existing equipment with a high yield.

[0044] Without being bound by any theory, the inventors of the present application found that the above-mentioned element proportion deviation and impurity phases are caused by unexpected fluctuations of elements in the raw materials, which are caused by the principle defects of the preparation device.

[0045] In the process of preparing perovskite crystals using the Bridgman method, a plurality of precisely proportioned powder raw materials need to be sealed in a quartz crucible with a vacuum degree of 10 -5 -10 -4 Pa to react. The opening of the commonly used quartz crucible is extended with a tubular structure for fixing on the vacuum sealing machine to vacuumize the inside of the crucible. In the actual device, the tubular structure needs to have a certain length to avoid the failure of the vacuum sealing rubber ring at the vacuum interface due to the ultra-high temperature applied by the flame gun during sealing.

[0046] The inventors found in the research that although the design of the tubular structure in the general device effectively and conveniently avoids the failure of the vacuum interface, it brings the following problems: in the process of loading the crucible through the long and narrow tubular structure, a part of the raw materials will inevitably adhere to the wall of the tube without entering the crucible after falling a distance, and part of the tube wall adhered with raw materials will be cut off when the crucible is taken off from the vacuum sealing machine after the sealing operation is completed. In this process, the raw materials loaded and retained in the crucible cannot guarantee that they still have the original proportion, resulting in deviation of the component ratio. Unfortunately, the performance of perovskite crystals related to radiation detection applications is very sensitive to the deviation of the raw material ratio. For example, for inorganic perovskite CsPbBr3, the raw materials are mixed by CsBr and PbBr2 powders. Among them, when CsBr is excessive, Cs4PbBr6 impurities will be formed, and when PbBr2 is excessive, CsPb2Br5 impurities will be formed. The formation of impurities leads to the formation of defects such as twinning during crystal growth, affecting the crystallization quality, and further limiting the performance of the crystal. Therefore, for the growth of high-quality inorganic perovskite single crystals, it is necessary to accurately determine the raw material ratio and avoid component deviation. Since the related technology has followed the mature Bridgman method equipment, there is no problem of raw material loss caused by the above-mentioned long tubular structure loading and further raw material ratio deviation and impurity generation problem, so it has not been optimized, and the problem of impurity generation has always been unable to be solved.

[0047] In addition, the inventors also found that the single-layer quartz tube structure is often used in the related technology, which cannot provide an effective temperature buffer zone, and the interface is easily disturbed during the Bridgman method crystal growth, thereby inducing stress cracks.

[0048] In addition, the inventors also found that in the growth process of perovskite single crystals containing volatile elements (such as Br elements), if the quartz tube is a single sealed cavity, it is difficult to flexibly control the local vapor pressure of the volatile element, thereby causing component segregation.

[0049] Based on the above findings, the inventors propose a double-layer crucible which can improve the above three problems and realize the industrialized production of perovskite crystals for room temperature nuclear radiation detection by the Bridgman method in an economical way.

[0050] In one embodiment, the present application provides a double-layer crucible, comprising:

[0051] an outer circular tubular container having an opening at the top;

[0052] an inner circular tubular container having an opening at the top, the maximum outer diameter of the inner circular tubular container being smaller than the inner diameter of the opening of the outer circular tubular container, so that the inner circular tubular container can be inserted into the outer circular tubular container through the opening of the outer circular tubular container;

[0053] a T-shaped cylindrical plug having a lower insertion section and an upper outer sealing section, the lower insertion section having an outer diameter smaller than an inner diameter of the opening of the inner cylindrical container, the upper outer sealing section having an outer diameter larger than an outer diameter of the opening of the inner cylindrical container and smaller than an inner diameter of the opening of the outer cylindrical container;

[0054] wherein, after inserting the lower insertion section of the T-shaped cylindrical plug into the opening of the inner cylindrical container such that the upper outer sealing section of the T-shaped cylindrical plug covers the opening of the inner cylindrical container and inserting the T-shaped cylindrical plug together with the inner cylindrical container into the outer cylindrical container from the opening of the outer cylindrical container, the outer cylindrical container has an extended passage between its opening and the upper outer sealing section of the T-shaped cylindrical plug.

[0055] The double-layered crucible can first solve the loss and proportion imbalance of the powder raw material for preparing perovskite crystals when the powder raw material is loaded into the crucible along the tubular structure of the narrow and long crucible opening. The double-layered crucible can also provide a vacuum cavity as a temperature buffer zone in the subsequent crystal growth process, reducing thermal disturbance at the crystal growth interface. The double-layered crucible can also be used for atmosphere control, compensating for element volatilization (such as halogen volatilization) that occurs during the growth of certain perovskite crystals, and alleviating composition segregation caused by element volatilization.

[0056] The double-layered crucible of the present application has a double-layer structure composed of an inner cylindrical container and an outer cylindrical container. The inner cylindrical container and the outer cylindrical container can be made of quartz and are preferably made of quartz. The advantage of quartz material is that it has stable chemical properties in the temperature range of crystal preparation and does not react with the raw material for preparing the crystal, and at the same time it is convenient to realize fusion sealing by flame method. In addition, it is easy to prepare, low in cost, and especially easy to mechanically cut.

[0057] Overall, the inner cylindrical container of the double-layered crucible of the present application is used to contain the reaction raw material, and the outer cylindrical container is used to connect with the vacuum sealing tube machine, so as to distribute the containing and connecting functions of the existing quartz crucible with a tubular structure to different parts.

[0058] In the present application, the "cylindrical container" is a container substantially in the shape of a cylinder. The cylindrical container has a vertical cylindrical body, with an opening at the top and a closed bottom. In this way, when the raw material is loaded therein, the raw material is loaded from the opening at the top and is located at the bottom of the cylindrical body. The vertically installed cylindrical container ensures uniform heating in each radial direction horizontally, which is required for the Bridgman method to obtain high-quality crystals. The cylindrical container can be composed of one or more parts with a circular periphery. For example, the cylindrical container can be a tube with a single constant cross-section, such as a straight circular tube, or it can be composed of several segments of circular tubes with different diameters connected one above the other, and its bottom can also have, for example, a conical, spherical or the like form.

[0059] The inner tubular container has a maximum outer diameter that is smaller than the inner diameter of the opening of the outer tubular container, so that the outer tubular container can be inserted into the outer tubular container through the opening of the outer tubular container. In this way, the raw material can be first loaded into the inner tubular container, and then the inner tubular container loaded with the raw material is placed into the outer tubular container through the opening of the outer tubular container, so that the inner tubular container is completely accommodated in the inner cavity of the outer tubular container.

[0060] The double-layered crucible of the present application also has a T-shaped cylindrical plug. The T-shape can also be referred to as a cross shape, which represents the vertical cross-sectional profile of the plug. The cylindrical shape represents the horizontal cross-sectional shape of the plug. The T-shaped cylindrical plug has a lower inner insertion section with a smaller diameter and an upper outer sealing section with a larger diameter. From the perspective of sealing with the inner and outer tubular containers, the T-shaped cylindrical plug is also preferably made of quartz.

[0061] The T-shaped cylindrical plug is matched with the inner walls of the inner and outer tubular containers. Specifically, the lower inner insertion section is configured to close the top opening of the inner tubular container, and the upper outer sealing section is configured to close the middle section of the outer tubular container. To this end, the diameter of the lower inner insertion section is smaller than the inner diameter of the opening of the inner tubular container, and the diameter of the upper outer sealing section is larger than the inner diameter of the opening of the inner tubular container and smaller than the inner diameter of the opening of the outer tubular container. The diameter of the lower inner insertion section is only slightly smaller than the inner diameter of the opening of the inner tubular container, for example, about 1 mm or less, so that it can be inserted into the opening of the inner tubular container, while it is easy to be fused with the inner wall of the opening of the inner tubular container by sealing to achieve sealing. Similarly, the diameter of the upper outer sealing section is smaller than the inner diameter of the opening of the outer tubular container and only slightly smaller than the inner diameter of the above-mentioned middle section, for example, about 1 mm or less, so that it can enter the opening of the outer tubular container, while it is easy to be fused with the inner wall of the outer tubular container by sealing to achieve sealing. In addition, the diameter of the upper outer sealing section is larger than the inner diameter of the opening of the inner tubular container, so that the opening of the inner tubular container can be completely covered. The diameter of the upper outer sealing section can be appropriately smaller than, equal to, or larger than the outer diameter of the opening of the inner tubular container.

[0062] When the lower inner plug section of the T-shaped cylindrical plug is inserted into the opening of the inner cylindrical container so that the upper outer sealing section of the T-shaped cylindrical plug covers the opening of the inner cylindrical container, and the T-shaped cylindrical plug is inserted into the outer cylindrical container together with the inner cylindrical container from the opening of the outer cylindrical container, the outer cylindrical container has an extended passage between its opening and the upper outer sealing section of the T-shaped cylindrical plug. Specifically, the extended passage can be the portion of the outer cylindrical container that is higher than the upper surface of the T-shaped cylindrical plug. In use, the opening of the outer cylindrical container is connected to a vacuum sealing machine, and the T-shaped cylindrical plug is kept away from the vacuum sealing machine by the extended passage. In this way, the heating and sealing of the T-shaped cylindrical plug will not affect the vacuum interface, and will not cause the sealing rubber ring at the vacuum interface to fail. In addition, after the T-shaped cylindrical plug is sealed with the inner wall of the outer cylindrical container, the operation on the extended passage (such as cutting it off so that it can be removed from the vacuum sealing machine) will not affect the portion below the T-shaped cylindrical plug and the raw materials therein.

[0063] In the use of this double-layer crucible, the reaction raw materials are first loaded into the inner cylindrical container. Then, after covering the inner cylindrical container with the T-shaped cylindrical plug, the whole is loaded into the outer cylindrical container. Next, the opening of the outer cylindrical container is connected to the vacuum sealing machine, and vacuum is performed. At this time, the contact between the T-shaped cylindrical plug and the top opening of the inner cylindrical container is not airtight, and the inner cylindrical container is not completely sealed, so that both the inner cylindrical container and the outer cylindrical container can reach a high vacuum.

[0064] After vacuumizing, the T-shaped cylindrical plug is sealed with the inner wall of the outer cylindrical container by heating, so that the space below the T-shaped cylindrical plug is isolated and sealed from the outside. Then, the outer cylindrical container can be separated from the vacuum sealing machine by cutting off the extended passage above the sealing position. Then, the desired crystal preparation reaction is performed by heating the outer cylindrical container.

[0065] Through this structure and operation mode, the extended passage connected to the vacuum sealing machine is arranged on the outer cylindrical container, and the function of loading raw materials is completed by the inner cylindrical container. All raw materials are retained in the inner cylindrical container, which can avoid the problem in the related art that the raw materials attached to the long and narrow tubular structure at the entrance of the crucible after falling a distance and are lost during the sealing and separation of the crucible, ensuring the accurate proportioning of the reaction raw materials, so as to realize the preparation of a pure-phase perovskite structure.

[0066] In addition, the double-layer structure of the present application can also flexibly select the temperature buffering function or the atmosphere regulating function through different sealing methods through the design of the T-shaped cylindrical plug.

[0067] To achieve the temperature buffering function, before or after the heating to realize the fusion sealing between the T-shaped cylindrical plug and the outer circular tubular container, the internal space of the inner circular tubular container is sealed by heating to realize the fusion sealing between the T-shaped cylindrical plug and the inner circular tubular container. Thus, a high-vacuum inter-container space is formed between the inner circular tubular container and the outer circular tubular container. Due to the high vacuum maintained, in the subsequent crystal preparation process, heat from the outside of the outer circular tubular container can only be transferred to the outer wall of the inner circular tubular container by radiation, and excellent temperature buffering function can be achieved.

[0068] To achieve the atmosphere control function, the sealing between the T-shaped cylindrical plug and the inner circular tubular container can not be performed, and the gas flow capability of the inner circular tubular container and the inter-container space is retained. At the same time, some compensation element materials are pre-loaded in the inner space of the outer circular tubular container. In this way, when the raw materials volatilize in the subsequent reaction, the compensation element materials in the outer circular tubular container also volatilize and supplement into the inner cavity of the inner circular tubular container. In this way, the vapor partial pressure of the volatilized element in the atmosphere can be increased by the element compensation from the outer circular tubular container, and the composition segregation caused by volatilization can be effectively inhibited. For example, when there is bromine element in the raw materials, it is easy to volatilize. At this time, some inorganic bromide salt can be pre-loaded on the inner wall of the outer circular tubular container to supplement the bromine element into the inner circular tubular container.

[0069] Thus, the double-layer crucible of the present application improves the aforementioned three problems.

[0070] In an embodiment, the wall thickness of the outer circular tubular container is 1.5 to 2 mm, and the opening outer diameter thereof ranges from 20 to 21 mm, and the maximum outer diameter of the inner circular tubular container is 16 mm or less. The opening outer diameter of the outer circular tubular container is suitable for interfacing with a conventional glass tube vacuum sealing machine. The outer diameter of the inner circular tubular container takes into account the wall thickness of the outer circular tubular container and can be easily loaded from the opening of the outer circular tubular container.

[0071] In an embodiment, the outer circular tubular container is divided into two parts, the upper half is used to connect the vacuum sealing machine and perform the fusion sealing operation, and the excess extension channel part above the sealing part is cut off after the fusion sealing operation is completed; the lower half is used to nest and fix the inner circular tubular container.

[0072] Preferably, the inner circular tubular container comprises an upper circular tube part and a lower circular cone part, wherein the bottom circle of the lower circular cone part has the same size as the cross section of the upper circular tube part, and

[0073] The outer circular tubular container comprises an upper circular tube part, a middle circular tube part and a lower circular cone part, wherein the inner diameter of the middle circular tube part is greater than that of the upper circular tube part, and the bottom circle of the lower circular cone part has the same size as the cross section of the middle circular tube part.

[0074] In this configuration, the outer cylindrical container has a middle cylindrical section with a larger diameter than the upper cylindrical section. In this way, when the main body of the inner cylindrical container is located in the wider middle cylindrical section, a cavity structure of the desired size can be formed outside the inner cylindrical container, while the top of the inner cylindrical container is located in the narrower upper cylindrical section of the outer cylindrical container, which is easy to fuse seal. In addition, since both have lower conical sections, when the bottom of the inner cylindrical container is inserted into the bottom of the outer cylindrical container, an annular gap region is formed, which naturally limits the concentricity and avoids direct contact between the two bottom end regions, which can cause thermal stress concentration. In addition, the apex of the conical shape is suitable for inducing the formation of a single crystal nucleus by the Bridgman method, for subsequent single crystal preparation operations.

[0075] Preferably, the taper angle of the lower conical section of the inner cylindrical container ranges from 30° to 45°;

[0076] The taper angle of the lower conical section of the outer cylindrical container ranges from 50° to 65° and is 10° to 25° larger than the taper angle of the lower conical section of the inner cylindrical container. This angle is easy to form a concentric limit, so that the inner and outer cylindrical containers are in the appropriate relative position.

[0077] Preferably, the inner diameter of the middle cylindrical section of the outer cylindrical container is 4mm to 10mm larger than the outer diameter of the upper cylindrical section of the inner cylindrical container. In this way, a cavity with a preferred radial width of 2mm to 5mm can be formed.

[0078] Preferably, the length of the extension channel section ranges from 120 to 150mm. For example, it can be about 130mm. The length in this range has the advantage of ensuring that the sealing rubber ring at the joint of the quartz tube and the vacuum sealing tube machine does not melt due to high heat conduction during sealing, resulting in a loss of vacuum.

[0079] In one embodiment, the length of the upper outer sealing section of the T-shaped cylindrical plug ranges from 10 to 15mm, and the diameter is 15 to 16mm; the length of the lower inner insertion section ranges from 10 to 15mm, and the diameter is 11 to 12mm. Overall, the two diameters of the T-shaped cylindrical plug are matched with the inner diameters of the outer and inner cylindrical containers, for example, about 1mm smaller. The above preferred length and diameter are beneficial for installation and fusion sealing.

[0080] When the opening of the inner cylindrical container is not fusion sealed with the T-shaped cylindrical plug, a vacuum pumping channel is maintained between the inner cylindrical container and the outer cylindrical container through the structural gap between the T-shaped cylindrical plug and the opening of the inner cylindrical container, so that when vacuum is pumped through the opening of the outer cylindrical container, the inner cylindrical container, the outer cylindrical container and the inter-container cavity can be simultaneously pumped to vacuum. When the inter-container cavity is used as a temperature buffer zone, the inner cylindrical container can be sealed before or after the outer cylindrical container is fusion sealed, so that the inner cylindrical container is isolated from the inter-container cavity. Preferably, the inner cylindrical container is fusion sealed first to ensure that the raw material cavity is vacuum sealed before the outer cylindrical container is fusion sealed. When the inter-container cavity is used as an atmosphere control zone, the gap between the inner cylindrical container and the quartz plug is maintained and only the outer cylindrical container is fusion sealed. By using quartz inner and outer cylindrical containers and a T-shaped cylindrical plug, the overall fusion sealing process can be completed in a relatively short time, avoiding thermal stress damage caused by temperature changes or gas disturbance.

[0081] The temperature buffer zone is used to delay heat conduction caused by gas conduction or convection, and to reduce thermal disturbance at the crystal growth interface. When used as an atmosphere control zone, dynamic compensation of halogen evaporation during crystal growth can be achieved by adding a stable material that sublimates to release halogen vapor in the inter-container cavity.

[0082] In one embodiment, the outer cylindrical container, the inner cylindrical container and the T-shaped cylindrical plug are all made of quartz. The advantages are as described above.

[0083] Figure 1A schematic diagram of one embodiment of the double-layered crucible is shown. As shown in the diagram, the double-layered crucible comprises an outer cylindrical container 1, a T-shaped cylindrical plug 2, and an inner cylindrical container 3. The inner cylindrical container 3 has a maximum outer diameter smaller than the inner diameter of the opening of the outer cylindrical container 1, and can be inserted into the outer cylindrical container 1. Both the outer cylindrical container 1 and the inner cylindrical container 3 depicted in the diagram have a preferably conical bottom, which cooperates with the T-shaped cylindrical plug 2 so that the inner cylindrical container 3 is stably positioned concentrically in the outer cylindrical container 1. However, other suitable bottom shapes are also feasible. The outer cylindrical container 1 shown in the diagram is composed of an upper cylindrical section 11, a middle cylindrical section 13, and a lower conical section 12. The inner diameter of the middle cylindrical section 13 is larger than that of the upper cylindrical section 11, and the bottom circle of the lower conical section 12 has the same size as the cross section of the middle cylindrical section 13. The inner cylindrical container 3 shown in the diagram is composed of an upper cylindrical section 31 and a lower conical section 32. The bottom circle of the lower conical section 32 has the same size as the cross section of the upper cylindrical section 31. The T-shaped cylindrical plug 2 is composed of an upper outer sealing section 21 and a lower inner insertion section 22. The upper outer sealing section 21 cooperates with the inner wall of the outer cylindrical container 1 and has a slightly smaller diameter, and can seal the inner cavity of the outer cylindrical container 1 from the outside space by fusion sealing. The lower inner insertion section 22 is inserted into the opening of the inner cylindrical container 3, so that the upper outer sealing section 21 covers the opening. The portion of the T-shaped cylindrical plug 2 above the upper outer sealing section 21 to the opening of the outer cylindrical container 1 that is to be connected to the vacuum sealing tube machine is an extended passage section with a length of L, and can be cut off in subsequent operations to separate the portion of the outer cylindrical container 1 containing the inner cylindrical container 3 from the vacuum sealing tube machine as a whole. Since the raw material is preloaded in the inner cylindrical container 3 and placed in the outer cylindrical container 1 after being covered by the T-shaped cylindrical plug, the problem of the raw material adhering to the inner wall of the extended passage section during falling does not occur, and the deviation of the proportion of the raw material caused by loading is avoided.

[0084] The inter-container cavity C between the outer cylindrical container 1 and the inner cylindrical container 3 can be independently sealed or communicated with the inner space R of the inner cylindrical container 3, depending on whether the T-shaped cylindrical plug is fusion sealed with the inner cylindrical container 3. Accordingly, the temperature buffering function or the atmosphere regulating function in cooperation with the compensating element material preloaded in the outer cylindrical container 1 can be achieved, respectively. The compensating element material can be deposited on the inner wall of the middle cylindrical section 13 of the outer cylindrical container 1 instead of being accumulated on the bottom of the outer cylindrical container 1, avoiding the formation of a material heat transfer path between the bottom of the outer cylindrical container 1 and the inner cylindrical container 3.

[0085] In one embodiment, the present application also provides a method for preparing a perovskite polycrystalline material using the double-layered crucible of the present application. Generally, after the T-shaped cylindrical plug is fusion-sealed to the outer cylindrical container 1 after being evacuated, the outer cylindrical container 1 is heated, such as rocking heating, to obtain the polycrystalline material. The polycrystalline material is then used in a subsequent Bridgman method to prepare a single crystal. It is difficult to directly use a mixture of various raw materials to prepare a single crystal by the Bridgman method. The step-by-step preparation method of first generating a polycrystalline material and then performing the Bridgman method can obtain an ideal product.

[0086] Specifically, the method for preparing a perovskite polycrystalline material comprises:

[0087] placing reaction raw materials of the perovskite polycrystalline material in the inner cylindrical container;

[0088] inserting the lower inner insertion section of the T-shaped cylindrical plug into the opening of the inner cylindrical container so that the upper outer sealing section of the T-shaped cylindrical plug covers the opening of the inner cylindrical container;

[0089] vertically inserting the T-shaped cylindrical plug and the inner cylindrical container into the outer cylindrical container;

[0090] connecting the opening of the outer cylindrical container to a vacuum pump;

[0091] evacuating using the vacuum pump;

[0092] fusion-sealing the upper outer sealing section of the T-shaped cylindrical plug to the inner wall of the outer cylindrical container; and

[0093] transforming the reaction raw materials into the perovskite polycrystalline material by heating the outer cylindrical container.

[0094] The reaction raw materials of the perovskite polycrystalline material can be any suitable raw material in the related art as long as it does not adversely affect the principles of the present application. For example, the raw materials can be a mixture of various salt powders. In one embodiment, the target perovskite material can be a lead halide type perovskite. Examples of the raw materials include: a mixture of lead bromide and cesium bromide with a molar ratio of 1:1, a mixture of cesium iodide, cesium bromide and lead bromide with a molar ratio of 0.1:0.9:1, a mixture of cesium chloride, cesium bromide and lead bromide with a molar ratio of 0.2:0.8:1, etc.

[0095] In the present application, the vacuum pump is the vacuum pump whose suction port matches the opening of the outer cylindrical container. Due to the presence of the extension passage portion, the heat fusion sealing operation of the T-shaped cylindrical plug does not affect the sealing ring and other components of the suction port of the vacuum pump.

[0096] In one aspect, as described above, after the vacuum is drawn by the vacuum pump, before or after the upper outer sealing section of the T-shaped cylindrical plug is fused to the inner wall of the outer circular tubular container, the lower inner insertion section of the T-shaped cylindrical plug is fused to the inner wall of the inner circular tubular container, forming an inter-container cavity (also referred to as an inter-tube cavity) as a temperature buffer zone.

[0097] An exemplary preferred embodiment of a polycrystalline synthesis method in which the inter-tube cavity functions as a temperature buffer zone can include the following steps.

[0098] First, the perovskite precursor raw materials are loaded into the inner circular tubular container in stoichiometric ratio in a nitrogen glove box with water and oxygen content <0.01 ppm; the T-shaped cylindrical plug is placed at the opening of the inner circular tubular container, and the inner circular tubular container and the T-shaped cylindrical plug are placed in the outer circular tubular container as a whole; the double-layered quartz crucible is removed from the glove box and quickly installed on the vacuum sealing machine, and the vacuum pump is turned on to draw a vacuum.

[0099] Subsequently, the vacuum degree is reduced to 10 -5 -10 -4 Pa, and the sealing is ready to be performed. First, the flame gun is aimed at the lower inner insertion section of the T-shaped cylindrical plug, and uniform rotation heating is performed to fuse and seal, and after ensuring that the inner circular tubular container is completely sealed, the flame gun is aimed at the upper outer sealing section of the T-shaped cylindrical plug to fuse and seal the outer circular tubular container. After the sealing operation is completely finished, the vacuum pump is turned off.

[0100] Finally, the completely sealed double-layered quartz crucible is placed in a rocking furnace, and the temperature is raised from room temperature to 580-600°C at a rate of 5-10°C / min, and the polycrystalline raw material is obtained by high-temperature rocking for 3-5h.

[0101] In another aspect, as described above, the volatile element compensation material is pre-loaded inside the outer circular tubular container, and the T-shaped cylindrical plug is not fused to the inner circular tubular container, forming an inter-container cavity as an atmosphere control zone.

[0102] An exemplary preferred embodiment of a polycrystalline synthesis method in which the inter-tube cavity functions as an atmosphere control zone can include the following steps.

[0103] First, the perovskite precursor raw materials are loaded into a quartz inner cylindrical container in a nitrogen glove box with water and oxygen content <0.01 ppm; a T-shaped quartz cylindrical container is placed at the opening of the quartz inner cylindrical container, and the quartz T-shaped cylindrical plug and the quartz inner cylindrical container are placed in a quartz outer cylindrical container; a small amount of high-purity inorganic halide salt (such as CsBr, KBr, etc.) is placed in the interlayer of the quartz inner cylindrical container and the quartz outer cylindrical container, and is preferably pre-deposited on the inner wall of the outer cylindrical container; the double-layered quartz crucible is taken out of the glove box and quickly installed on a vacuum sealing machine, and the vacuum pump is turned on to perform vacuumization.

[0104] Subsequently, the vacuum degree is reduced to 10 -5 -10 -4 Pa, and the sealing process is ready to be performed. The flame gun is aimed at the outer sealing section of the quartz T-shaped cylindrical plug, and uniform rotation heating is performed for sealing. After the sealing operation is completely finished, the vacuum pump is turned off.

[0105] Finally, the completely sealed double-layered quartz crucible is placed in a powder mixer, and is mixed at room temperature for 10-15 h to obtain a powder-like polycrystalline raw material.

[0106] Regardless of whether the inner cylindrical container is sealed and pre-loaded with volatile element compensation materials, the use of a double-layered crucible structure can achieve that the powder only contacts the inner wall of the inner cylindrical container, and the outer wall of the outer cylindrical container is free of powder adhesion. Compared with the traditional single-layered sealing and loading method, the loss of raw materials caused by the adhesion of powder to the outer wall of the extension pipe at the opening of the crucible during the loading process is solved, and the component control accuracy and material consistency are improved.

[0107] By adjusting the size design of the inner and outer cylindrical containers and changing the distance between the inner and outer cylindrical containers, the inter-container cavity formed can be used as a temperature buffer zone to avoid the influence of temperature mutation on the crystal growth interface, and can also absorb the deformation caused by the different step of thermal expansion of the inner and outer cylindrical containers at high temperatures.

[0108] The inter-container cavity between the inner and outer cylindrical containers can be expanded for atmosphere control during crystal growth. A small amount of high-purity inorganic halide salt is added to the cavity, and a small air gap is reserved between the inner and outer cylindrical containers by adjusting the sealing process to compensate for the volatilization of halogen during crystal growth.

[0109] In one embodiment, the present application also provides a preparation method of a perovskite single crystal. Specifically, the aforementioned polycrystalline material preparation method is performed to obtain a perovskite polycrystalline material in the inner cylindrical container, and then a Bridgman method is performed on the perovskite polycrystalline material in the double-layered crucible to convert the perovskite polycrystalline material into a perovskite single crystal.

[0110] Bridgman method is to make the heated crucible and low temperature zone in the vertical direction relative movement, so that the polycrystalline material in the molten from the bottom to the top gradually into the low temperature zone to achieve bulk single crystal growth.

[0111] Specifically, after the aforementioned two groups of steps (1) - (3), the following step (4) can be carried out:

[0112] After the polycrystalline material synthesis, the double-layer quartz crucible is directly placed in the crystal growth furnace for crystal growth. In particular, the crystal furnace heating rate is not more than 10 ℃ / min to prevent local stress.

[0113] Embodiment

[0114] Double-layer crucible preparation example

[0115] A double-layer crucible is prepared for a component with the following dimensions.

[0116] The outer circular tubular container wall of quartz is 2 mm thick, the outer diameter of the upper half (upper circular tube part) is 20 mm, and the length is 150 mm; the outer diameter of the lower half (including the middle circular tube part and the lower circular cone part) is 27 mm, and the length is 150 mm, and the bottom cone angle is 55°.

[0117] The inner circular tubular container wall of quartz is 1.5 mm thick, the total length is 160 mm, the outer diameter is 15 mm, and the bottom cone angle is 35°.

[0118] At this time, the difference between the bottom cone angles of the inner and outer circular tubular containers is 20°, and the cavity thickness between the containers is 4 mm.

[0119] The outer sealing segment of the T-shaped cylindrical plug of quartz is 15 mm in diameter and 10 mm in length; the inner insertion segment is 11 mm in diameter and 10 mm in length. After the inner circular tubular container with the T-shaped cylindrical plug is placed in the outer circular tubular container, the length of the extended passage part is 130 mm.

[0120] Example 1 (inter-tube cavity used as temperature buffer zone):

[0121] Experiments are carried out using the crucible prepared in the crucible preparation example. In a nitrogen glove box with water and oxygen content <0.01 ppm, perovskite precursor raw materials are loaded into the quartz inner circular tubular container according to the stoichiometric ratio; the quartz T-shaped cylindrical plug is placed at the opening of the quartz inner circular tubular container, and then the quartz T-shaped cylindrical plug and the quartz inner circular tubular container are placed in the quartz outer circular tubular container as a whole; the above double-layer quartz crucible is taken out from the glove box and quickly installed on a vacuum sealing machine, and a vacuum pump is started to perform vacuumizing. The formula of the perovskite precursor raw materials is 12.78 g of cesium bromide and 22.02 g of lead bromide.

[0122] The vacuum degree is reduced to 10 -5 -10 -4Prepare for sealing at Pa. First, aim the flame gun at the inner section of the quartz T-shaped cylindrical plug and heat it evenly by rotating to ensure the inner tubular quartz container is completely sealed. Then, aim the flame gun at the outer sealing section of the quartz T-shaped cylindrical plug to seal the outer tubular quartz container. After the sealing operation is completely completed, turn off the vacuum pump.

[0123] A completely sealed double-layered quartz crucible was placed in a gyratory furnace and heated from room temperature to 590°C at a rate of 5°C / min. The crucible was then gyratory at high temperature for 5 hours to obtain polycrystalline raw materials.

[0124] After the polycrystalline material is synthesized, the double-layered quartz crucible is directly placed in a crystal growth furnace for single-crystal growth using the Bridgman process. Specifically, the furnace heating rate is 5°C / min to prevent localized stress.

[0125] The obtained material was analyzed by X-ray diffraction (XRD) to obtain... Figure 2 The diffraction pattern shown is compared with the peak positions of the standard card ICSD 97851 for the target perovskite material, and a one-to-one correspondence can be observed. This indicates that no other impurity phases are present. This demonstrates that the use of the double-layer crucible of the present invention does not result in problems of raw material loss or imbalance in the crucible.

[0126] The obtained single crystal was energized at room temperature, and its voltage-current correlation was measured under X-ray irradiation and without X-ray irradiation. The results are shown in... Figure 3 In this context, photocurrent is the current under standard X-ray irradiation, while dark current is the current in the absence of X-ray irradiation. The difference between photocurrent and dark current indicates the sensitivity of the single crystal to radiation detection. It can be seen that the photocurrent is an order of magnitude higher than the dark current, indicating that the obtained single crystal has excellent room-temperature radiation detection sensitivity.

[0127] Example 2 (inter-tube cavity used as an atmosphere control zone):

[0128] The crucible prepared using the crucible preparation example was used in the experiment. In a nitrogen glove box with a water oxygen content <0.01 ppm, the perovskite precursor raw material was stoichiometrically loaded into a quartz inner tubular container; a quartz T-shaped cylindrical stopper was placed at the opening of the quartz inner tubular container, and then the quartz T-shaped cylindrical stopper and the quartz inner tubular container were placed together in a quartz outer tubular container; 0.2 mg of high-purity cesium bromide was placed in the interlayer between the quartz inner and outer tubular containers; the double-layered quartz crucible was removed from the glove box, quickly installed on a vacuum sealing machine, and the vacuum pump was turned on to evacuate the container. The perovskite precursor raw material formulation was a mixture of 1.56 g of cesium iodide, 11.50 g of cesium bromide, and 22.02 g of lead bromide.

[0129] Vacuum level drops to 10 -5 -10-4 Prepare for tube sealing at Pa. Aim the flame gun at the outer sealing section of the quartz T-shaped cylindrical plug and rotate evenly to heat and melt the seal. Turn off the vacuum pump only after the sealing operation is complete.

[0130] A completely sealed double-layered quartz crucible was placed in a powder mixer and shaken and mixed at room temperature for 15 hours to obtain powdered polycrystalline raw materials.

[0131] After the polycrystalline material is synthesized, the double-layered quartz crucible is directly placed in a crystal growth furnace for single-crystal growth using the Bridgman process. Specifically, the furnace heating rate is 8°C / min to prevent localized stress.

[0132] The obtained material was analyzed by X-ray diffraction (XRD) to obtain... Figure 4 The diffraction pattern shown is compared with the peak positions of the standard card ICSD 97851 for the target perovskite material, and a one-to-one correspondence can be observed. This indicates that no other impurity phases are present. This demonstrates that the use of the double-layer crucible of the present invention does not result in problems of raw material loss or imbalance in the crucible.

[0133] The obtained single crystal was energized at room temperature, and its voltage-current correlation was measured under X-ray irradiation and without X-ray irradiation. The results are shown in... Figure 5 As can be seen, the photocurrent is an order of magnitude higher than the dark current, indicating that the obtained single crystal has excellent room-temperature radiation detection sensitivity.

[0134] Comparative Example 1

[0135] Single crystals were prepared by the Bridgman process using a conventional quartz crucible with a tubular structure, with the same formulation and heating parameters as in Example 1.

[0136] The obtained material was analyzed by X-ray diffraction (XRD) to obtain... Figure 6 The diffraction pattern shown is compared with the peak positions of the standard ICSD 97851 card for the target perovskite material. It can be seen that the peak positions do not correspond one-to-one. This indicates the presence of other impurity phases, causing raw material loss and imbalance.

[0137] The obtained single crystal was energized at room temperature, and its voltage-current correlation was measured under X-ray irradiation and without X-ray irradiation. The results are shown in... Figure 7 As can be seen, compared with Example 1, the increase in photocurrent is less than that in dark current, indicating that the resulting single-crystal X-ray irradiation has a weaker light response and poorer room temperature radiation detection sensitivity.

[0138] Comparative Example 2

[0139] A single crystal was prepared by Bridgman method using a conventional quartz crucible with a tubular structure, with the same formulation and heating parameters as in Example 2.

[0140] The obtained material was detected by X-ray diffraction (XRD), and a diffraction spectrum as shown in FIG. 2 was obtained. Figure 8 By comparing the peak position with the standard card ICSD 97851 of the target perovskite material, it can be seen that the peak positions do not correspond one by one. This indicates that other impurities appear, causing the problem of loss and imbalance of raw materials.

[0141] The obtained single crystal was powered at room temperature, and the voltage-current relationship was measured in the presence and absence of X-ray irradiation, and the results are shown in FIG. 3. Figure 9 It can be seen that compared with Example 2, the photocurrent is less increased than the dark current, indicating that the obtained single crystal has weak light response under X-ray irradiation and poor room temperature radiation detection sensitivity.

[0142] From the comparison of the above examples and comparative examples, it can be seen that the present application can prepare single crystals with higher quality by Bridgman method, and can realize the practicality of perovskite materials in radiation detection. The key to successfully realize the Bridgman method lies in the inner and outer tube double-layer structure of the present application, which ensures the accurate proportion of raw materials. In addition, the design of the thermal buffer cavity reduces the temperature disturbance in the crystal growth process. The cavity between the inner and outer tubes can be expanded for atmosphere adjustment, reducing the adverse effects of volatile raw materials. The two ways can further improve the quality of single crystals for different raw materials.

[0143] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and any skilled person in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A double-layered crucible, characterized by, The double-layer crucible comprises: an outer circular tubular container having an opening at the top; an inner circular tubular container having an opening at the top, the maximum outer diameter of the inner circular tubular container being smaller than the inner diameter of the opening of the outer circular tubular container, so that the outer circular tubular container can be inserted into the outer circular tubular container through the opening of the outer circular tubular container; a T-shaped cylindrical plug having a lower inner insertion section and an upper outer sealing section, the diameter of the lower inner insertion section being smaller than the inner diameter of the opening of the inner circular tubular container, and the diameter of the upper outer sealing section being larger than the inner diameter of the opening of the inner circular tubular container and smaller than the inner diameter of the opening of the outer circular tubular container; wherein, after the lower inner insertion section of the T-shaped cylindrical plug is inserted into the opening of the inner circular tubular container so that the upper outer sealing section of the T-shaped cylindrical plug covers the opening of the inner circular tubular container, and the T-shaped cylindrical plug is inserted into the outer circular tubular container together with the inner circular tubular container from the opening of the outer circular tubular container, the outer circular tubular container has an extended passage between its opening and the upper outer sealing section of the T-shaped cylindrical plug.

2. The double-layer crucible according to claim 1, wherein the wall thickness of the outer circular tubular container is 1.5-2 mm, the outer diameter of the opening of the outer circular tubular container is 20-21 mm, and the maximum outer diameter of the inner circular tubular container is 16 mm or less.

3. The double-layer crucible according to claim 1, wherein the inner circular tubular container comprises an upper circular tubular section and a lower conical section, wherein the bottom circle of the lower conical section has the same size as the cross section of the upper circular tubular section, and the outer circular tubular container comprises an upper circular tubular section, a middle circular tubular section, and a lower conical section, wherein the inner diameter of the middle circular tubular section is larger than the inner diameter of the upper circular tubular section, and the bottom circle of the lower conical section has the same size as the cross section of the middle circular tubular section.

4. The double-layer crucible according to claim 3, wherein the taper angle of the lower conical section of the inner circular tubular container is 30-45°; the taper angle of the lower conical section of the outer circular tubular container is 50-65°, and is 10-25° larger than the taper angle of the lower conical section of the inner circular tubular container.

5. The double-layer crucible according to claim 3, wherein the inner diameter of the middle circular tubular section of the outer circular tubular container is 4-10 mm larger than the outer diameter of the upper circular tubular section of the inner circular tubular container.

6. The double-layer crucible according to claim 1, wherein the length of the extended passage is 120-150 mm.

7. The double-layer crucible according to claim 1, wherein the length of the upper outer sealing section of the T-shaped cylindrical plug is 10-15 mm, and the diameter is 15-16 mm; the length of the lower inner insertion section is 10-15 mm, and the diameter is 11-12 mm.

8. A method for preparing perovskite polycrystalline material using the double-layer crucible according to claim 1, comprising: placing the reaction raw materials of perovskite polycrystalline material in the inner circular tubular container. inserting a lower inner plug section of the T-shaped cylindrical plug into the opening of the inner cylindrical container such that an upper outer seal section of the T-shaped cylindrical plug covers the opening of the inner cylindrical container; vertically inserting the T-shaped cylindrical plug together with the inner cylindrical container into the outer cylindrical container; connecting the opening of the outer cylindrical container to a vacuum pump; using the vacuum pump to create a vacuum; fusion sealing the upper outer seal section of the T-shaped cylindrical plug to the inner wall of the outer cylindrical container; and transforming the reaction raw material into the perovskite polycrystal material by heating the outer cylindrical container.

9. The method of claim 8, wherein, The method further comprises: fusion sealing the lower inner plug section of the T-shaped cylindrical plug to the inner wall of the inner cylindrical container after or before fusion sealing the upper outer seal section of the T-shaped cylindrical plug to the inner wall of the outer cylindrical container after using the vacuum pump to create a vacuum.

10. The method of claim 8, wherein, The method further comprises: preloading a volatile element compensating material inside the outer cylindrical container.

11. A method for producing a perovskite single crystal, characterized by comprising: The preparation method comprises: performing the method of claim 8 to obtain a perovskite polycrystal material in the inner cylindrical container, performing a Bridgman method on the perovskite polycrystal material in the double-layered crucible to transform the perovskite polycrystal material into a perovskite single crystal.

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