Integrated sintering vessel for synthesis of chalcogenide polycrystals and method of manufacture

Abstract

The application discloses a one-piece sintering synthesis container for synthesizing chalcogen compound polycrystal and a preparation method, which comprises a quartz reaction cavity and a quartz bearing container, the quartz bearing container is tightly nested with a graphite crucible with an upper end opening and a lower end closure; the quartz reaction cavity and the quartz bearing container are connected into one piece by oxyhydrogen flame sintering to form an integral structure which cannot be disassembled; the graphite crucible is used for loading metal elements Ba, Ga and Ge, and the inside of the quartz reaction cavity is used for loading elemental S; a gas extraction pipe is used for connecting a vacuum system and is sealed by oxyhydrogen flame after vacuumizing. The synthesis container combines with temperature control, so that a large amount of S is at a temperature lower than the boiling point, the corrosion of Ba to quartz is avoided, the safety of the synthesis process is improved, and the risk of explosion of the synthesis container is prevented. The application effectively improves the purity and phase uniformity of the synthesized polycrystal, and provides high-quality raw materials for subsequent high-quality single crystal growth.

Description

Technical Field

[0001] This invention relates to the field of inorganic functional materials preparation technology, specifically to a method for synthesizing polycrystalline chalcogenide raw materials for infrared nonlinear optical crystals, particularly a high-purity, single-phase Ba₂Ga₈GeS₂. 16 Methods for synthesizing polycrystalline materials. Background Technology

[0002] Ba2Ga8GeS 16 Barium digallium germanium sulfide (Ba2Ga8GeS) is a mid-to-far infrared nonlinear optical crystal material with excellent performance discovered in recent years. For example, patent JP7751851B2 discloses an infrared optical parametric oscillator using Ba2Ga8GeS. 16 Infrared parametric oscillators using crystals and specific mirrors can efficiently generate high-power mid-infrared light, overcoming the limitations of traditional systems by improving durability and reducing cost. (Ba2Ga8GeS) 16 With its wide light transmission range, large nonlinear coefficient, and high laser damage threshold, it has significant application prospects in the field of infrared laser frequency conversion.

[0003] Synthesis of high-quality Ba2Ga8GeS 16 Polycrystalline synthesis is a crucial step in the Bridgman process for growing single crystals. Currently, the synthesis of such complex multi-component sulfide polycrystalline materials typically employs a direct high-temperature reaction method, where elemental Ba, Ga, Ge, and S are placed in a quartz ampoule in stoichiometric proportions, sealed under vacuum, and then directly heated to a high temperature for the reaction. However, this method has significant drawbacks: 1. Violent Exothermic Reactions and Safety Concerns: The boiling point of sulfur (S) is 445℃, while the actual reaction temperature is much higher, easily generating a large vapor pressure that could cause the synthesis container to explode. Furthermore, sulfur reacts violently with highly reactive metals such as Ba and Ga at high temperatures, instantly producing large amounts of gas and heat, causing a rapid increase in internal pressure within the quartz ampoule, which can easily lead to an explosion, posing an extremely high risk. Metallic Ba readily reacts with quartz, corroding the synthesis container and also potentially causing it to explode.

[0004] 2. Prone to the formation of impurity phases: The four elements Ba, Ga, Ge, and S have vastly different reactivity and melting and boiling points. During a one-step heating process, thermodynamically more stable binary or ternary intermediate phases (such as Ga2S3, BaS, GeS2, etc.) are readily formed. These intermediate phases are very stable and difficult to react completely at subsequent high temperatures to form the target quaternary phase, resulting in a large number of impurity phases in the final product.

[0005] Existing techniques use elements to synthesize binary compounds Ga2S3, BaS, and GeS2, and then use these as raw materials for high-temperature solid-state synthesis of Ba2Ga8GeS. 16Polycrystalline synthesis involves very complex steps, and the high-temperature solid-state reaction is prone to incomplete reaction, resulting in the presence of binary or ternary impurities in the product.

[0006] 3. Deviation of component volatility from stoichiometry: S and GeS2 are highly volatile at high temperatures and easily condense at the cold end of the ampoule, causing the stoichiometry in the reaction zone to deviate significantly from the nominal ratio, making it impossible to obtain a phase-pure product.

[0007] Therefore, it is necessary to develop a safe, controllable method for synthesizing high-phase pure Ba2Ga8GeS. 16 The polycrystalline method is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a safe, reliable, high-purity, and phase-uniform integral sintering container and its preparation method for synthesizing polycrystalline chalcogenides, particularly Ba2Ga8GeS. 16 Methods for preparing polycrystalline materials.

[0009] The objective of this invention is achieved through the following technical solution: An integrally sintered container for synthesizing polycrystalline chalcogenides, comprising: The quartz reaction chamber is a quartz tube with a hollow convex bottom at the bottom and an upper end for connecting to the evacuation pipe. The quartz support container is a quartz crucible that is open at the top and closed at the bottom. Its inner diameter is the same as that of the quartz reaction chamber. A graphite crucible that is open at the top and closed at the bottom is tightly nested inside the container. The outer diameter of the graphite crucible matches the inner diameter of the quartz crucible. The quartz reaction chamber and the quartz support container are sintered together by an oxyhydrogen flame to form an integral structure that cannot be disassembled. The graphite crucible is used to load the metallic elements Ba, Ga, and Ge, and the interior of the quartz reaction chamber is used to load elemental S. The evacuation pipe is used to connect to the vacuum system, and after evacuation, it is sealed by an oxyhydrogen flame.

[0010] As a preferred embodiment, the inner cavity of the hollow convex bottom is connected to the inner cavity of the graphite crucible, so that the quartz reaction chamber, the hollow convex bottom, and the graphite crucible together constitute a sealed reaction space.

[0011] As a preferred embodiment, the evacuation pipe, after being connected to a vacuum pump, evacuates the sealed reaction space to a vacuum level of ≤10. - 3 Pa.

[0012] As a preferred embodiment, the inner diameter of the quartz reaction chamber (1) is 30-60 mm.

[0013] As a preferred embodiment, the inner diameter of the hollow convex bottom is 15-20 mm.

[0014] As a preferred embodiment, the outer diameter of the extraction pipe is 12 mm.

[0015] As a preferred embodiment, the quartz reaction chamber includes a main body section, a connecting pipe section, and a vacuum pipe section; the main body section is a cylindrical chamber for containing elemental sulfur; the connecting pipe section is a hollow quartz tube, the upper end of which is connected to the bottom center of the main body section, and the lower end of which is sealed to the upper opening of the quartz support container; the vacuum pipe section is connected to the top of the main body section for connecting to a vacuum system.

[0016] As a preferred embodiment, the main body section, connecting pipe section, and air extraction pipe section are integrally formed quartz structures.

[0017] As a preferred embodiment, the length of the connecting pipe section is 30 mm.

[0018] A Ba2Ga8GeS 16 The preparation method of polycrystalline materials includes the following steps: (1) Provide an integrally sintered container; (2) Weigh out the elemental Ba, Ga, Ge and S with a purity of 6N according to the stoichiometric ratio Ba:Ga:Ge:S=2:8:1:16; (3) Use a flexible funnel to load elemental S into the quartz reaction chamber, and use a long funnel to load elemental Ba, Ga and Ge into the graphite crucible; (4) Connect the vacuum pipe to the vacuum system and evacuate to ≤10. -3 Pa, then the extraction pipe was sealed with an oxyhydrogen flame, and a quartz hook was welded at the seal to obtain a sealed synthetic container; (5) The synthesis container is placed vertically in a dual-temperature zone synthesis furnace, wherein the upper temperature zone is referred to as zone I and the lower temperature zone is referred to as zone II; (6) Control the temperature of region I to rise to 350-450℃ within 20-30 hours, and simultaneously control the temperature of region II to rise to 1000-1100℃ within 20-30 hours. Maintain the temperature for 48-60 hours, so that S continuously migrates from region I to region II through gas phase transport and reacts with Ba, Ga, and Ge to form Ba2Ga8GeS. 16 ; (7) After the S reaction is basically complete, raise the temperature of zone I to 1050-1150℃ and keep the temperature of zone II at 1000-1100℃. Continue to keep warm for 24 hours to suppress the component segregation caused by the volatilization and desolvation of the volatile component GeS2 in the product during the subsequent cooling process.

[0019] The present invention has at least the following beneficial effects: The synthesis container, combined with temperature control, not only keeps a large amount of sulfur below its boiling point, preventing Ba corrosion of quartz and improving the safety of the synthesis process, but also effectively enhances the synthesis of Ba₂Ga₈GeS by promoting the full progress of the gas-solid-liquid multiphase reaction. 16 The purity and phase uniformity of polycrystalline materials provide high-quality raw materials for subsequent high-quality single-crystal growth. Attached Figure Description

[0020] To reveal the technical details of the embodiments of the present invention, the accompanying drawings involved in the embodiments will be briefly described below. It should be emphasized that these drawings only present several embodiments of the present invention and should not be considered as defining the scope of the invention. For those skilled in the art, other related drawings can still be derived based on these drawings without inventive effort.

[0021] Figure 1 The following are schematic diagrams of different stages of the synthesis container in the embodiments of the present invention, wherein (1) the quartz assembly part of the synthesis container, (2) the part of the synthesis container containing the graphite crucible, (3) the schematic diagram of the synthesis container before it is assembled and before it is filled, and (4) the schematic diagram of the synthesis container after it is filled, vacuumed and sealed. In the figure, 1-quartz reaction chamber, 2-quartz support container, 3-raw material S, 4-raw materials Ba, Ge, Ga, 5-temperature zone I, 6-temperature zone II. Detailed Implementation

[0022] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the following description.

[0023] In the following description, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. However, it should be understood that the present disclosure is not limited to the specific forms shown herein. Rather, it should be understood to encompass various variations, equivalents, and / or alternatives to the embodiments of the present disclosure. In illustrating the drawings, the same reference numerals will be used to denote similar components.

[0024] It should be clarified that while the following description provides detailed specific information to aid in a comprehensive understanding of the exemplary embodiments, those skilled in the art will recognize that the exemplary embodiments can be implemented even without these specific details. For example, the system may be illustrated using block diagrams to avoid excessive detail that could obscure the clarity of the example. In other cases, to maintain the clarity of the example, unnecessary details of well-known processes, structures, and techniques may be omitted.

[0025] like Figure 1As shown, an integrally sintered container for synthesizing polycrystalline chalcogenides includes: Quartz reaction chamber 1, which is a quartz tube with a hollow convex bottom and an upper end for connecting to the air extraction pipe; The quartz support container 2 is a quartz crucible with an open top and a closed bottom. Its inner diameter is the same as that of the quartz reaction chamber 1. A graphite crucible with an open top and a closed bottom is tightly nested inside it. The outer diameter of the graphite crucible matches the inner diameter of the quartz crucible. The quartz reaction chamber 1 and the quartz support container 2 are connected as one unit by sintering with an oxyhydrogen flame to form an integral structure that cannot be disassembled. The graphite crucible is used to load the metallic elements Ba, Ga, and Ge, such as... Figure 1 The raw materials Ba, Ge, and Ga4 are used in the process, and the interior of the quartz reaction chamber 1 is used to load elemental S. Figure 1 Raw material S3; The evacuation pipe is used to connect to the vacuum system. After evacuation, it is sealed by an oxyhydrogen flame, and a quartz hook is welded to the seal.

[0026] One-piece sintered container specifically designed for the synthesis of substances such as Ba2Ga8GeS 16 Designed for polycrystalline chalcogenide materials, its core structure consists of two parts: an upper quartz reaction chamber 1 and a lower quartz support container 2. The quartz reaction chamber is a quartz tube with a vacuum tube connected to the upper end for evacuation and loading, and a hollow convex bottom at the lower end. The quartz support container is a quartz crucible with an open upper end and a closed lower end, inside which a matching graphite crucible is tightly nested. The two are sintered at high temperature using an oxyhydrogen flame to form a completely sealed, non-removable unit. In use, elemental sulfur (S) is loaded into the upper quartz reaction chamber, while the metallic raw materials barium (Ba), gallium (Ga), and germanium (Ge) are placed in the lower graphite crucible. Since gallium is liquid at room temperature and readily forms a liquid phase at high temperatures, while sulfur volatilizes into vapor in large quantities when heated to around 400°C, the entire container is placed vertically in a dual-temperature zone furnace. The upper part maintains a lower temperature (approximately 400°C) to allow sulfur to continuously vaporize, while the lower part maintains a high temperature (approximately 1040°C) to keep the metal in a highly reactive state. The sulfur vapor diffuses downwards, passing through the hollow convex bottom into the high-temperature zone, where it undergoes a gas-solid-liquid multiphase reaction with liquid gallium, solid barium, and germanium, gradually generating the target product. This design cleverly physically isolates volatile sulfur from the active metal, avoiding violent side reactions, while utilizing the temperature difference to drive the directional transport of sulfur, ensuring a stable and complete reaction. After the reaction is complete, the extraction pipe is sealed with an oxyhydrogen flame and welded with quartz hooks for suspension annealing, ultimately obtaining a high-quality polycrystalline material with uniform composition and few impurities.

[0027] The core innovation of this invention lies in the synergistic effect of spatial isolation and programmed temperature rise to actively control the reaction pathway of a multi-component sulfide system, allowing it to bypass thermodynamically stable but non-target binary or ternary impurities and directly generate single-phase Ba2Ga8GeS. 16 This strategy is based on a quantitative analysis of the changes in the Gibbs free energy of each competing reaction with temperature.

[0028] Consider the following key responses: Target quaternary phase formation reaction: 2Ba + 8Ga + Ge + 16S → Ba2Ga8GeS 16 Typical heterogeneous phase formation reactions: 2Ba+S2→2BaS 2Ga + 3S → Ga2S3 Ge+2S→GeS2 The above reaction at temperature Standard molar Gibbs free energy variation (unit: K) (unit: This can be represented as: ; in, For standard molar enthalpy change of reaction ( ); For standard molar reaction entropy change ( ); is the absolute temperature (K).

[0029] Thermodynamic calculations show that BaS and GazSs The K value is significantly less than zero below 500K, indicating that the reaction occurs very readily; while Ba₂Ga₈GeS 16 The formation of these phases requires a temperature above 1000K to provide sufficient driving force. If all raw materials are mixed and then directly heated at high temperatures, Ba and Ga will preferentially react with S to rapidly form kinetically favorable binary phases such as BaS and GaZSs. These phases have dense structures and slow diffusion, making it difficult for them to fully participate in the quaternary reaction in subsequent high-temperature stages, resulting in residual impurities in the product.

[0030] This invention avoids this problem by doing the following: (1) Spatial isolation: S is placed in the upper quartz cavity, and Ba, Ga and Ge are placed in the lower graphite crucible. The two do not come into contact during the loading and initial heating stages. (2) Timing control: First, raise the lower temperature zone (zone II) to 1000–1100°C to make the metal in a highly active molten or solid solution state, while the upper temperature zone (zone I) is only raised to 350–450°C to make S slowly vaporize; (3) Directional transport: S vapor continuously enters the high-temperature zone through the hollow convex bottom, and directly participates in the nucleation of the quaternary phase in the environment of excessive active metal, avoiding the precipitation of the binary phase caused by local S excess.

[0031] Therefore, this invention does not simply "slow down the reaction," but rather constructs a non-equilibrium reaction path that bypasses the impurity phase energy barrier, ensuring the single-phase nature of the product from both thermodynamic and kinetic dimensions. This path relies on the precise coupling of the integrated sintering vessel's structural design and the dual-temperature zone temperature control process, which is impossible to achieve with existing one-step sealed synthesis methods.

[0032] In a preferred embodiment, the inner cavity of the hollow convex bottom is connected to the inner cavity of the graphite crucible, so that the quartz reaction chamber 1, the hollow convex bottom, and the graphite crucible together constitute a sealed reaction space.

[0033] The hollow convex bottom of the container is the key channel connecting the upper quartz reaction chamber and the lower graphite crucible. Its internal hollow structure is directly connected to the inner cavity of the graphite crucible, thus integrating the two originally separate chambers into a single, continuous whole. After evacuation and sealing, the entire system forms a completely sealed reaction space, including the upper quartz chamber for holding elemental sulfur, the middle hollow convex bottom channel, and the lower graphite crucible for holding the metal raw materials. This design allows sulfur, after being heated and volatilized, to pass smoothly through the hollow convex bottom in vapor form, transported from the upper low-temperature zone to the lower high-temperature reaction zone, where it fully contacts and reacts with Ba, Ga, and Ge. Simultaneously, the sealed environment effectively prevents the leakage of toxic or volatile components (such as sulfur and GeS2), ensuring the stability of the stoichiometry of the reaction and avoiding component segregation due to component loss, thereby ensuring the final acquisition of high-purity, homogeneous polycrystalline materials.

[0034] In a preferred embodiment, the evacuation pipe, after being connected to a vacuum pump, evacuates the sealed reaction space to a vacuum level of ≤10. -3 Pa.

[0035] The evacuation pipe is the only channel connecting the synthesis vessel to the external vacuum system. After the raw materials are loaded, this pipe connects the entire sealed reaction space to the vacuum pump, removing internal air and moisture and reducing the internal pressure to 10. -3 The vacuum level is Pascal (Pa) or lower. This high vacuum environment is crucial: on the one hand, it effectively removes oxygen and water vapor, preventing the oxidation or hydrolysis of metallic raw materials (such as barium and gallium) at high temperatures; on the other hand, it avoids interference from impurity gases with the gas-phase transport process of sulfur, ensuring the purity of the reaction system. More importantly, at such low pressure, elemental sulfur can volatilize and diffuse more smoothly and controllably during heating, without residual gases hindering its migration path. After vacuuming is completed, the evacuation pipe is immediately sealed with an oxyhydrogen flame, completely sealing the entire reaction system and providing a clean, stable, and leak-free reaction environment for subsequent high-temperature synthesis.

[0036] In a preferred embodiment, the inner diameter of the quartz reaction chamber 1 is 30-60 mm, and this size is determined according to the amount of synthetic material used.

[0037] In a preferred embodiment, the inner diameter of the hollow convex bottom is 15-20 mm.

[0038] In a preferred embodiment, the outer diameter of the extraction pipe is 12 mm.

[0039] In a preferred embodiment, both the quartz reaction chamber 1 and the quartz support container 2 are cylindrical structures with open tops before sintering.

[0040] In a preferred embodiment, the elemental S is loaded into the interior of the quartz reaction chamber (1) through the suction pipe; the metallic elements Ba, Ga and Ge pass through the quartz reaction chamber (1) and the hollow convex bottom in sequence through the suction pipe, and finally fall into the graphite crucible.

[0041] In a preferred embodiment, the quartz reaction chamber 1 includes a main body section, a connecting pipe section, and a vacuum pipe section; the main body section is a cylindrical chamber for containing elemental sulfur; the connecting pipe section is a hollow quartz tube, the upper end of which is connected to the bottom center of the main body section, and the lower end is sealed to the upper opening of the quartz support container 2; the vacuum pipe section is connected to the top of the main body section for connecting to a vacuum system.

[0042] The quartz reaction chamber 1 is not a simple straight tube, but rather an integrated three-part structure: a top evacuation pipe section, a middle main body section, and a bottom connecting pipe section. The main body section is a cylindrical chamber specifically designed to hold elemental sulfur; its top connects to the evacuation pipe section for easy vacuuming and sealing; and a hollow connecting pipe section extends from the center of the bottom, inserting downwards and sealingly connecting to the upper opening of the quartz support container 2. This design ensures a clear and continuous internal flow throughout the reaction system: when heated, sulfur evaporates into vapor in the main body section, which then flows smoothly through the connecting pipe section into the graphite crucible area containing the metal raw materials, achieving directional gas-phase transport. Furthermore, the integrated quartz structure not only ensures structural stability at high temperatures but also avoids the risk of thermal stress cracking or leakage at the interfaces, thus ensuring the reaction proceeds efficiently in a completely sealed and clean environment.

[0043] In a preferred embodiment, the main body section, connecting pipe section, and exhaust pipe section are integrally formed quartz structures.

[0044] In a preferred embodiment, the length of the connecting pipe section is 30 mm.

[0045] In a preferred embodiment, the quartz reaction chamber 1 includes: a main body section, which is a cylindrical chamber with an inner diameter of 30-60 mm and a height of 60 mm; a connecting pipe section, which is a hollow quartz tube, the first end of which is connected to and passes through the bottom center of the main body section, and the second end of which is used to connect to the quartz support container 2; the inner diameter of the connecting pipe section is 15-20 mm and the length is 30 mm; and a vacuum pipe section, the first end of which is connected to and passes through the top of the main body section, and the second end of which is used to connect to the vacuum system; the outer diameter of the vacuum pipe section is 12 mm.

[0046] In a preferred embodiment, the quartz support container 2 is a quartz crucible with a total height of 340 mm; the graphite crucible has a total height of 300 mm, and its outer diameter matches the inner diameter of the quartz crucible so that the graphite crucible is tightly placed inside the quartz crucible.

[0047] In a preferred embodiment, to further improve the mass transfer efficiency between the liquid and solid phases of Ba, Ga, and Ge, and to suppress compositional inhomogeneity caused by local aggregation of liquid metal during the high-temperature reaction, a micro-flow-guiding network structure is processed on the inner bottom surface of the graphite crucible. This structure consists of multiple interconnected micron-sized grooves arranged in a crisscrossing grid or radial pattern, covering the central area of ​​the crucible bottom (within a diameter ≤ 12 mm).

[0048] The grooves have a depth of 0.2–0.6 mm, a width of 0.3–1.0 mm, and a spacing of 1.0–3.0 mm. All grooves are blind grooves (i.e., they do not penetrate the bottom wall of the crucible) and are located only on the inner surface of the graphite crucible, ensuring that the overall mechanical strength of the crucible is not affected and completely preventing liquid metal from leaking to the outer wall of the quartz support container 2.

[0049] During the reaction, when the temperature in zone II rises to 1000–1100°C, Ga and Ba form a highly fluid liquid alloy. Ge partially dissolves in the melt, while the undissolved portion is dispersed in the melt as fine solid particles. Under the influence of surface tension and wetting, the melt spontaneously fills the grooves in the micro-channel network and expands outwards along the channels, forming a thin liquid film. Sulfur vapor enters from above through the hollow convex bottom and can fully contact this expanding liquid film, significantly increasing the gas-liquid-solid three-phase reaction interface area. Simultaneously, Ge solid particles settle in the gaps between the channels and are encapsulated by the liquid metal, accelerating their dissolution and sulfidation kinetics.

[0050] The graphite crucible employing the aforementioned microfluidic network structure can significantly improve the performance of Ba2Ga8GeS. 16Uniformity and reaction efficiency in polycrystalline synthesis. Compared with traditional crucibles with smooth bottoms, the purity of the target phase in the obtained product is significantly improved, and the content of impurity phases is significantly reduced; the elemental distribution is more uniform, and compositional segregation is effectively suppressed. In addition, because the liquid alloy spreads at the bottom to form a larger reaction interface, the solid-liquid-gas three-phase contact is more complete, making the reaction more complete. Under the same process conditions, higher quality polycrystalline raw materials can be obtained, or the holding time can be appropriately shortened while ensuring product quality, which is beneficial to improving production efficiency.

[0051] In a preferred embodiment, an integrally sintered container is used for the synthesis of a chemical formula Ba2Ga8GeS. 16 Chalcogenide polycrystalline materials.

[0052] A Ba2Ga8GeS 16 The preparation method of polycrystalline materials includes the following steps: (1) Provide an integrally sintered container; (2) Weigh out the elemental Ba, Ga, Ge and S with a purity of 6N according to the stoichiometric ratio Ba:Ga:Ge:S=2:8:1:16; (3) Use a flexible funnel to load elemental S into the quartz reaction chamber (1), and use a long funnel to load elemental Ba, Ga and Ge into the graphite crucible; (4) Connect the vacuum pipe to the vacuum system and evacuate to ≤10. -3 Pa, then the extraction pipe was sealed with an oxyhydrogen flame and a quartz hook was welded at the seal to obtain a sealed synthetic container (4). (5) The synthesis container (4) is placed vertically in a dual-temperature zone synthesis furnace, wherein the upper temperature zone is denoted as Zone I (e.g., Figure 1 Temperature zone I is 5), and the lower temperature zone is denoted as zone II (e.g., Figure 1 Temperature Zone II (6) (6) Control the temperature of region I to rise to 350-450℃ (e.g., 400℃) within 20-30 hours, and simultaneously control the temperature of region II to rise to 1000-1100℃ (e.g., 1040℃) within 20-30 hours. Maintain the temperature for 48-60 hours, allowing S to continuously migrate from region I to region II via gas-phase transport, and react with Ba, Ga, and Ge to form Ba2Ga8GeS. 16 ; To achieve controllable vaporization and safe transport of elemental sulfur, this invention precisely controls the temperature of the upper temperature zone (Zone I) within the range of 350°C to 450°C. This temperature window is selected based on the thermodynamic relationship between the saturated vapor pressure of sulfur and temperature, avoiding the risk of container rupture due to a sudden increase in vapor pressure while ensuring that sulfur can continuously migrate to the high-temperature reaction zone at a stable rate.

[0053] saturated vapor pressure of sulfur (Unit: Pa) and absolute temperature (Unit: K) Satisfies the following Clausius-Clapeyron equations: ; in, This is the saturated vapor pressure of elemental sulfur, expressed in Pascals (Pa). The molar enthalpy of vaporization of sulfur, taking a value of ; Let be the ideal gas constant, with a value of . ; Absolute temperature, measured in Kelvin (K). This is the integration constant, determined by experimental calibration.

[0054] Calculations show that: when (i.e., at 350°C) Pa; when At K (i.e., 450°C), Pa. Although the latter is close to atmospheric pressure, in the high vacuum initial environment used in this invention... Under sealed quartz container conditions, sulfur vapor can diffuse smoothly without generating instantaneous high pressure. More importantly, because sulfur is placed in the upper quartz cavity, while the highly reactive metals Ba, Ga, and Ge are isolated in the lower graphite crucible, there is no direct contact between the two during the initial heating stage, thus completely avoiding the explosion risk caused by the violent exothermic reaction between S and Ba in the traditional one-step method. Therefore, this invention achieves integrated control of the slow release, transport, and reaction of sulfur through temperature zone setting guided by thermodynamic formulas, constituting a fundamental improvement that distinguishes it from existing technologies.

[0055] (7) After the S reaction is basically complete, raise the temperature of zone I to 1100℃ and keep the temperature of zone II at 1040℃. Continue to keep warm for 24 hours to suppress the component segregation caused by the volatilization and desolvation of the volatile component GeS2 in the product during the subsequent cooling process.

[0056] This preparation method aims to synthesize high-quality Ba2Ga8GeS. 16 The polycrystalline material processing involves seven main steps. First, a monolithically sintered container is provided, consisting of a quartz reaction chamber and a graphite crucible, sealed together using an oxyhydrogen flame to form a closed space. Next, elemental Ba, Ga, Ge, and S with a purity of 6N are precisely weighed according to the stoichiometric ratio Ba:Ga:Ge:S = 2:8:1:16. Elemental S is loaded into the quartz reaction chamber using a flexible funnel, while elemental Ba, Ga, and Ge are loaded into the graphite crucible using a long funnel. Finally, the container's evacuation pipe is connected to a vacuum system, and a vacuum of ≤10 °C is created. -3Pa is used to remove air and impurities, and then the extraction pipe is sealed with an oxyhydrogen flame and a quartz hook is welded to the seal to ensure that the entire container is completely sealed.

[0057] Next, the sealed synthesis container is placed vertically in a dual-temperature zone synthesis furnace, with the upper part designated as Zone I and the lower part as Zone II. The heating program is initiated, controlling the temperature of Zone I to rise to 400°C within 20–30 hours, while simultaneously raising the temperature of Zone II to 1040°C within the same timeframe, and holding at this temperature for 48–60 hours. During this process, sulfur volatilizes into vapor in the lower-temperature Zone I and is transported to the higher-temperature Zone II through the hollow channels inside the container. There, it undergoes a gas-solid-liquid multiphase reaction with barium, gallium, and germanium, gradually generating the target product Ba₂Ga₈GeS. 16 After the sulfur reaction is basically complete, the temperature of zone I is further increased to 1100℃, while the temperature of zone II remains unchanged (1040℃), and the process is continued for 24 hours. This stage helps to homogenize the product composition, suppress the volatilization and desolvation of the volatile component GeS2 during cooling, and avoid product segregation, ultimately obtaining a high-purity, homogeneous polycrystalline material. This design not only simplifies the operation process but also effectively improves the quality and stability of the product.

[0058] In a preferred embodiment of the present invention, to solve the problem of Ba2Ga8GeS 16 To address the microcrack problem caused by thermal stress concentration after high-temperature synthesis of polycrystalline materials, and to further improve the density and mechanical integrity of the product, after completing the heat preservation reaction in step (7), the synthesis container is not immediately removed; instead, a programmed gradient cooling annealing process is initiated. Specifically, the dual-temperature zone furnace is controlled to cool synchronously at different rates: the lower temperature zone (zone II) at a rate... The temperature drops slowly, with the upper heating zone (Zone I) cooling at an even slower rate. Cooling down, maintaining the axial temperature difference at A small positive gradient of K is applied until the overall temperature drops below 400°C, after which the furnace naturally cools to room temperature. This gradient cooling strategy effectively releases the internal stress caused by the anisotropy of thermal expansion of the material and the mismatch at the quartz-graphite interface by actively controlling the spatial distribution and temporal evolution of the temperature field. Its thermodynamic basis can be quantitatively described by the following thermal stress model: ; in, This represents the maximum thermal stress inside the polycrystalline column, measured in Pascals (Pa). Ba2Ga8GeS 16 The effective Young's modulus of polycrystalline materials is taken as: Pa; Let be the average linear expansion coefficient of the material, and take a value of . ; This is Poisson's ratio, with a value of 0.25; This represents the absolute value of the temperature gradient along the container's axial direction (z-direction), expressed in Kelvin per meter (K·m). -1 ); This represents the height of the reaction column, typically 0.08m.

[0059] In traditional rapid cooling processes, Can exceed 500 km·m -1 ,lead to MPa, far exceeding the material's tensile strength (approximately 15 MPa), triggered microcracks. We addressed this by controlling the temperature... Controlled at <100 K·m -1 ,make MPa significantly inhibits cracking. The polycrystalline bulk material treated in this way has a smooth surface without visible cracks and a density close to the theoretical value, providing a highly reliable raw material for subsequent Bridgman single crystal growth.

[0060] In summary, this invention provides a uniquely structured, process-controllable, integrally sintered container and its application in Ba2Ga8GeS2 16 A method for preparing polycrystalline materials was developed. By physically isolating the sulfur source and metal raw materials in space, and combining a dual-temperature-zone programmed heating and a closed-loop gas-phase transport mechanism, the severe side reactions caused by direct contact between highly reactive metals and sulfur were effectively avoided, while the formation of thermodynamically preferred but non-target binary impurity phases was suppressed. Furthermore, by introducing a micro-channeling network structure at the bottom of the graphite crucible, the uniformity of liquid-solid phase mass transfer at high temperatures was significantly improved; coupled with a gradient cooling annealing process, the problem of microcracks caused by thermal stress was effectively alleviated. The entire scheme was synergistically optimized from multiple dimensions, including container structure design, loading method, vacuum sealing, temperature control strategy, and post-processing, achieving the controllable preparation of high-quality, high-purity, and uniformly composed quaternary chalcogenide polycrystalline materials. This provides a reliable material basis for subsequent single-crystal growth and optoelectronic performance research, demonstrating outstanding substantive features and significant progress.

[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Those skilled in the art, based on an understanding of the core concept of the present invention, can make various equivalent substitutions, structural changes, or process adjustments to the above embodiments. Any modifications, combinations, simplifications, or improvements made based on the technical essence of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A one-piece sintered container for synthesizing polycrystalline chalcogenides, characterized in that, include: Quartz reaction chamber (1), which is a quartz tube with a hollow convex bottom at the bottom and an upper end for connecting to the gas extraction pipe; The quartz support container (2) is a quartz crucible with an open top and a closed bottom. Its inner diameter is the same as that of the quartz reaction chamber (1). A graphite crucible with an open top and a closed bottom is tightly nested inside. The outer diameter of the graphite crucible matches the inner diameter of the quartz crucible. The quartz reaction chamber (1) and the quartz support container (2) are connected as one unit by sintering with an oxyhydrogen flame to form an integral structure that cannot be disassembled. The graphite crucible is used to load the metallic elements Ba, Ga and Ge, and the interior of the quartz reaction chamber (1) is used to load the elemental S. The evacuation pipe is used to connect to the vacuum system, and after evacuation, it is sealed by an oxyhydrogen flame.

2. The integrally sintered container according to claim 1, characterized in that, The inner cavity of the hollow convex bottom is connected to the inner cavity of the graphite crucible, so that the quartz reaction chamber (1), the hollow convex bottom and the graphite crucible together form a closed reaction space.

3. The integrally sintered container according to claim 1, characterized in that, The extraction pipe, after being connected to a vacuum pump, evacuates the sealed reaction space to a vacuum level of ≤10. -3 Pa.

4. The integrally sintered container according to claim 1, characterized in that, The inner diameter of the quartz reaction chamber (1) is 30-60 mm.

5. The integrally sintered container according to claim 1, characterized in that, The inner diameter of the hollow convex bottom is 15-20 mm.

6. The integrally sintered container according to claim 1, characterized in that, The outer diameter of the extraction pipe is 12mm.

7. The integrally sintered container according to claim 1, characterized in that, The quartz reaction chamber (1) includes a main body section, a connecting pipe section, and a vacuum pipe section; the main body section is a cylindrical chamber used to contain elemental S; the connecting pipe section is a hollow quartz tube, the upper end of which is connected to the bottom center of the main body section, and the lower end is sealed to the upper opening of the quartz support container (2); the vacuum pipe section is connected to the top of the main body section and is used to connect to a vacuum system.

8. The integrally sintered container according to claim 7, characterized in that, The main body, connecting pipe, and exhaust pipe are integrally formed quartz structures.

9. The integrally sintered container according to claim 7 or 8, characterized in that, The length of the connecting pipe section is 30mm.

10. A Ba2Ga8GeS 16 The method for preparing polycrystalline materials is characterized by, Includes the following steps: (1) Provide an integrally sintered container; (2) Weigh out the elemental Ba, Ga, Ge and S with a purity of 6N according to the stoichiometric ratio Ba:Ga:Ge:S=2:8:1:16; (3) Use a flexible funnel to load elemental S into the quartz reaction chamber (1), and use a long funnel to load elemental Ba, Ga and Ge into the graphite crucible; (4) Connect the vacuum pipe to the vacuum system and evacuate to ≤10. -3 Pa, then the extraction pipe was sealed with an oxyhydrogen flame, and a quartz hook was welded at the seal to obtain a sealed synthetic container; (5) The synthesis container is placed vertically in a dual-temperature zone synthesis furnace, wherein the upper temperature zone is referred to as zone I and the lower temperature zone is referred to as zone II; (6) Control the temperature of region I to rise to 350-450℃ within 20-30 hours, and simultaneously control the temperature of region II to rise to 1000-1100℃ within 20-30 hours. Maintain the temperature for 48-60 hours, so that S continuously migrates from region I to region II through gas phase transport and reacts with Ba, Ga, and Ge to form Ba2Ga8GeS. 16 ; (7) After the S reaction is basically complete, raise the temperature of zone I to 1050-1150℃ and keep the temperature of zone II at 1000-1100℃. Continue to keep warm for 24 hours to suppress the component segregation caused by the volatilization and desolvation of the volatile component GeS2 in the product during the subsequent cooling process.

Images