Method for preparing and purifying germanium ingot based on reduction, zone melting and crystal pulling integrated technology

Abstract

The invention provides a method for preparing and purifying a germanium ingot based on a reduction, zone melting and crystal pulling integrated technology, which comprises the processes of charging, segmented hydrogen reduction, heating device switching, zone melting and crystal pulling integrated purification, blowing-out discharging and the like, and the processes of reduction, zone melting and the like are synchronously realized in a self-made reduction-purification integrated device. The energy consumption is greatly reduced and the efficiency is improved; meanwhile, in the zone-melting purification process, N-type non-doped single crystals are used for induction zone-melting, that is, the dual impurity removal effects of zone-melting and crystal pulling are achieved in the zone-melting process, and high-purity germanium ingots with higher quality can be produced easily, efficiently and at low cost; the method has the remarkable advantages of coherent and simplified process, energy conservation, efficiency improvement, product qualification rate improvement and the like.

Description

Technical Field

[0001] This invention relates to the field of refining and purifying rare dispersed metal germanium, specifically to a method for preparing and purifying germanium ingots based on an integrated reduction, zone melting, and crystal pulling technology. Background Technology

[0002] Germanium is a high-value rare and dispersed metal and a strategic metal, an important component of modern high-tech new materials. It is widely used in high-tech fields such as defense, aerospace, electronics, optoelectronics, medicine, energy, and modern information technology, playing a crucial role in the development of national strategic emerging industries. The products of germanium production at various stages include germanium metal and its compounds, which are designed for specific applications. The utility of germanium is attributed to at least five significant properties: ① Germanium is an intrinsic semiconductor, effective as a conductor at high frequencies and low operating voltages; ② Germanium exhibits transparency to a portion of the infrared electromagnetic spectrum; ③ Germanium is a glass former, capable of forming more or less randomly ordered extended three-dimensional networks of germanium-oxygen tetrahedra; ④ Germanium has a high refractive index; ⑤ It exhibits low dispersion. These five properties, individually or sometimes in combination, determine the wide range of practical applications for germanium in fields such as fiber optic communication, infrared optics, polymerization catalysts, electronics, and solar energy. Other applications include chemotherapy, metallurgy, and phosphors.

[0003] High-purity germanium ingots are one of the main germanium products on the market, primarily used as raw materials for germanium single crystals. Their resistivity requirement is ≥50Ω·cm at 20±0.5℃, with a purity reaching 5~8N. The existing traditional process involves reducing high-purity germanium dioxide with hydrogen in a reduction furnace to produce reduced germanium ingots, which are then purified by zone melting in a zone furnace to obtain high-purity germanium ingots. High-purity germanium dioxide is first dried and calcined, then reduced in a quartz tube of a reduction furnace at 650-680℃ with hydrogen to obtain metallic germanium powder. At the end of the reduction, the temperature can be gradually increased to 1000-1100℃ to melt the germanium, and then it is slowly cooled to obtain reduced germanium ingots. Typically, the resistivity of the reduced germanium ingots produced is 1-20 Ω·cm, with more than 80% of the content being in the region, and the purity is 4-6N. The reduced germanium ingots need to be further purified, and the zone melting method is usually used for purification. This method is widely used in industrialization. The mainstream equipment in industrialization is a horizontal zone melting furnace for zone melting purification, with hydrogen and nitrogen as the protective atmosphere.

[0004] The reduction and zone melting processes described above need to be carried out separately in two sets of equipment: a reduction furnace and a zone melting furnace. As a result, the production efficiency is low and the energy consumption is high. Moreover, the purification is carried out using a polycrystalline zone melting purification method. The pass rate of the zone-melted germanium ingots obtained after a single round of zone melting purification is usually around 60%. The unqualified part needs to be returned for two or more rounds of zone melting purification. There is considerable room for improvement and enhancement in purification efficiency. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies by proposing a method for preparing and purifying germanium ingots based on an integrated reduction, zone melting, and crystal pulling technology. This invention develops a method for preparing and purifying germanium ingots based on an integrated reduction, zone melting, and crystal pulling technology. This innovative method integrates reduction and zone melting in the same equipment, significantly reducing energy consumption and improving efficiency. Simultaneously, during the zone melting purification process, N-type undoped single crystals are used to induce zone melting, achieving a dual impurity removal effect of zone melting and crystal pulling during the zone melting process. This allows for the simple, efficient, and low-cost production of higher-quality, high-purity germanium ingots.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing and purifying germanium ingots based on an integrated reduction, zone melting, and crystal pulling technology, wherein the specific steps of the method are as follows: S1: Pre-treatment of loading: Germanium single crystal seed crystals are loaded into the AB section of the graphite boat, high-purity germanium dioxide is placed into the BC section of the graphite boat, and the graphite boat containing the materials is placed in a self-made "reduction-purification integrated device". The graphite boat is the core high-temperature resistant molding carrier that supports the germanium ingot; The AB segment of the graphite boat refers to the continuous segment from point A to point B on the graphite boat; the BC segment refers to the continuous segment from point B to point C on the graphite boat; point B is the core point where the melting zone initially forms, and point C is the termination point of the horizontal movement of the melting zone. The AB and BC segments are two carrier segments on the graphite boat divided along the direction of movement of the melting zone, and are the main carrier areas for placing germanium ingots and completing zone melting crystal pulling and purification.

[0007] Germanium single crystal seed and high-purity germanium dioxide are placed in separate, adjacent areas in a graphite boat. During the subsequent reduction and zone melting processes, the germanium dioxide is reduced to germanium metal, which is then fused with the interface between the germanium single crystal seed and the germanium metal seed.

[0008] S2: Segmented controllable hydrogen reduction: Open the inlet valve and the outlet valve, and introduce inert gas into the device for a period of time through the inlet to purge the air inside the device; stop introducing inert gas and introduce high-purity hydrogen into the device. The resistance heater is turned on to heat the BC section of the graphite boat. The first stage of heating raises the temperature to the set temperature and then holds it. The second stage of heating raises the temperature to the set temperature and then holds it. The third stage of heating raises the temperature to the set temperature and then holds it. The fourth stage of heating raises the temperature to the set temperature and then holds it.

[0009] Using a self-made integrated reduction-purification device, reduction is achieved by directional heating of the area containing high-purity germanium dioxide in a graphite boat and the introduction of high-purity hydrogen gas. The first stage of heating, with a controlled temperature of 550–680°C, aims to evaporate the small amounts of moisture and volatiles in the germanium dioxide while controlling the evaporation rate to prevent excessively rapid evaporation from blowing the germanium dioxide out of the graphite boat. Simultaneously, a small amount of germanium dioxide is slowly reduced to germanium powder. The second stage of heating, with a controlled temperature of 680–750°C, aims to reduce most of the high-purity germanium dioxide to germanium powder while maintaining an appropriate reaction rate. The first stage involves heating at 750–890°C to prevent excessively high temperatures and rapid reactions that could lead to insufficient germanium dioxide production and the loss of germanium monoxide, which would then be carried away by the gas flow. During this stage, most of the germanium dioxide is reduced to germanium powder. The second stage involves heating at 1000–1150°C to rapidly melt the germanium powder into a liquid state. This is done to prevent excessively high temperatures from causing the germanium powder to melt and coat the germanium dioxide, thus affecting the reduction efficiency. During this stage, the germanium dioxide is completely reduced to germanium powder. The third stage involves heating at 1000–1150°C to rapidly melt the germanium powder into a liquid state.

[0010] In this step, all the germanium dioxide in the graphite boat is reduced to germanium metal, and the reaction equations are shown in equations (1) to (3), and it exists in a liquid state. The reaction equation is as follows: GeO2 +H2 = GeO + H20 (1); GeO + H2 = Ge + H20 (2); GeO2 + 2H2 = Ge + 2H20 (3).

[0011] S3: Switch heating device: Reduce the flow rate of high-purity hydrogen, turn off the resistance heater, and move it to the rear of the furnace. After all the germanium in the graphite boat has condensed into a solid, move the high-frequency induction coil horizontally to a position on the same vertical plane as point B.

[0012] The reduction process and the zone melting process are switched on the same equipment, and the liquid germanium generated by the reduction in step S2 in the graphite boat is condensed into solid germanium polycrystalline material, which is then fused with the germanium single crystal seed crystal in the graphite boat near point B.

[0013] S4: Integrated purification of zone melting and crystal pulling: The width of the germanium ingot melting zone inside the graphite boat is controlled by setting the heating power of the high-frequency induction coil, and the impurity removal effect of zone melting and crystal pulling is controlled by setting its horizontal running speed. The high-frequency induction coil first heats the area near point B of the graphite boat with high-frequency induction, causing germanium to melt and form a molten zone while germanium remains solid on both sides of the molten zone. Then, it moves horizontally and uniformly from the vertical plane of point B to the vertical plane of point C, causing the melting zone of germanium to move synchronously and uniformly. Subsequently, the high-frequency induction coil stops heating and automatically returns to the initial position of the vertical plane of point B, completing one zone melting and crystal pulling purification cycle. By repeating this cycle a set number of times, the zone melting and crystal pulling purification of the germanium ingot can be completed in this round.

[0014] By heating the corresponding area of ​​the graphite boat with a high-temperature induction coil and moving it horizontally, the regional melting and purification of germanium was achieved. By inducing the process by pre-placing germanium single crystal seed crystals in the area from A to B of the graphite boat, the crystal pulling process was realized at the same time as the zone melting. Since the crystal pulling process itself has the function of removing impurities, this step achieves the dual impurity removal function of zone melting and crystal pulling, which greatly improves the purification efficiency.

[0015] S5: Shutdown and discharge: After the "reduction-purification integrated device" has cooled down initially, the hydrogen gas is turned off and an inert gas is introduced. The device continues to cool naturally to no more than 150°C before the inert gas is introduced. The inlet valve and the outlet valve are closed. The furnace continues to cool naturally to a lower temperature range before the "reduction-purification integrated device" is opened. Germanium ingots can be obtained from the graphite boat inside the device. After testing, qualified parts are cut off and sold as zone-melted germanium ingots after conventional surface treatment. The unqualified germanium ingots that are cut off can be used as raw materials for the production of zone-melted germanium ingots for further purification.

[0016] Hydrogen is used to reduce and protect the surface of the germanium ingot during the cooling process; inert gas is introduced to remove the hydrogen from the furnace and provide a safety guarantee for the ingot to be taken out of the furnace after cooling.

[0017] Preferably, in step S1, the germanium single crystal seed crystal used should meet the quality requirements of N-type undoped germanium single crystal in GB / T5238 "Germanium Single Crystal and Germanium Single Crystal Wafer", and the high-purity germanium dioxide used should meet the requirements of various quality indicators of high-purity germanium dioxide of GeO2-05 and above in YS / T11069 "High-purity germanium dioxide".

[0018] Preferably, in step S2, the inert gas introduced is nitrogen or argon, and the nitrogen or argon is introduced for 10-30 minutes; then the inert gas is stopped, and the flow rate of high-purity hydrogen is introduced at 1000-6000 L / h; the first stage of heating is raised to 550-680℃ and held at that temperature for 2-4 hours; the second stage of heating is raised to 680-750℃ and held at that temperature for 2-6 hours; the third stage of heating is raised to 750-890℃ and held at that temperature for 2-6 hours; and the fourth stage of heating is raised to 1000-1150℃ and held at that temperature for 1-3 hours.

[0019] Preferably, in step S3, the flow rate of high-purity hydrogen is reduced to 400~1500L / h.

[0020] Preferably, in step S4, the heating power of the high-frequency induction coil is adjusted to control the width of the melting zone to be 2-4 cm, the speed of the high-frequency induction coil moving horizontally and uniformly from the same vertical plane as point B to the same vertical plane as point C is controlled to be 20-40 cm / h, and the number of cycles of zone melting and crystal pulling purification is set to be 2-5 times.

[0021] Preferably, in step S5, when the integrated reduction-purification device cools down to no more than 450°C, the hydrogen gas is turned off and nitrogen or argon gas is introduced. When the temperature continues to drop to no more than 150°C, the introduction of nitrogen or argon gas is stopped. After cooling down to no more than 50°C, the integrated reduction-purification device is opened, and germanium ingots can be obtained from the graphite boat inside the device. After testing, qualified parts are cut off and sold as zone-melted germanium ingots after conventional surface treatment, which meet the requirements of various quality indicators of zone-melted germanium ingots of grade ZGe-0 and above in GB / T11071 "Zone-melted Germanium Ingots". Unqualified germanium ingots can be used as raw materials for further purification in the production of zone-melted germanium ingots.

[0022] An integrated reduction-purification device for preparing and purifying germanium ingots based on a combined reduction, zone melting, and crystal pulling technology includes a furnace body, a resistance heater, a high-frequency induction coil, a graphite boat, an air inlet, and an exhaust outlet. The furnace body is a sealed cavity structure. The graphite boat is horizontally embedded in the central region of the furnace body, with its length direction aligned with the axis of the furnace body. A safety gap of approximately ~cm is maintained between the graphite boat and the inner wall of the furnace body. The resistance heater and the high-frequency induction coil are respectively movably connected to the side wall of the furnace body via external translation drive mechanisms, and the trajectory of the translation drive mechanisms is parallel to the length direction of the graphite boat. The resistance heater is moved to the corresponding heating position outside the BC section of the graphite boat, and the high-frequency induction coil is moved to the working position corresponding to the same vertical plane as point B of the graphite boat and the entire length of the BC section. When not in operation, both are located in the avoidance area at the rear of the furnace body and do not interfere with each other. The air inlet and exhaust outlet are respectively opened on the end walls of both ends of the furnace body and are connected to the sealed cavity of the furnace body. The exhaust end of the air inlet extends to the side of the furnace body near end A of the graphite boat, and the air inlet end of the exhaust outlet extends to the side of the furnace body near end C of the graphite boat, forming a gas flow channel along the length of the graphite boat. An air inlet valve is provided on the air inlet, and an exhaust outlet valve is also provided on the exhaust outlet.

[0023] The furnace body is made of quartz and is used to place materials and perform reduction, zone melting, and crystal pulling on the materials. The resistance heater can heat the corresponding area of ​​the graphite boat in the furnace body through resistance heating. The high-frequency induction coil can locally heat the graphite boat through high-frequency induction, thereby indirectly heating the germanium metal in the graphite boat locally. The air inlet is connected to the furnace body and is equipped with an air inlet valve for introducing inert gas or high-purity hydrogen into the "integrated reduction-purification device". The exhaust port is connected to the furnace body and is equipped with an exhaust port valve for discharging the waste gas in the "integrated reduction-purification device" to the waste gas treatment system.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention integrates the reduction, zone melting and crystal pulling processes into the same equipment for continuous operation through a self-made reduction-purification integrated device, eliminating the need to transfer materials between multiple sets of equipment, greatly shortening the production cycle, reducing equipment investment and energy consumption costs, and significantly improving production efficiency compared with traditional processes. Secondly, in the zone melting purification process, the pre-placed N-type undoped germanium single crystal seed crystal is used for induction, simultaneously achieving the dual impurity removal effect of zone melting and crystal pulling, effectively removing impurity elements in germanium, and increasing the qualified rate of zone melting germanium ingots to over 78%, with a maximum of 88.2%, which is far higher than the qualified rate of about 60% of traditional processes.

[0025] Furthermore, the products obtained by this method meet the quality requirements of ZGe-0 and above grades in GB / T11071 "Zone-melted Germanium Ingots", exhibiting excellent resistivity and purity, which can meet the stringent requirements of high-purity germanium ingots in high-tech fields such as optical fiber communication, infrared optics, and electronics. At the same time, unqualified germanium ingots can be returned to the system as raw materials for further purification, resulting in high material utilization, reduced production costs, and reduced waste emissions, which aligns with the concept of green production. Attached Figure Description

[0026] Figure 1 A schematic diagram of the reduction process in the integrated reduction-purification device; Figure 2 A schematic diagram of the zone melting and crystal pulling process in the integrated reduction-purification unit; In the diagram: 1-furnace body; 2-resistance heater; 3-high frequency induction coil; 4-graphite boat; 5-air inlet; 6-exhaust outlet; 7-air inlet valve; 8-exhaust outlet valve. Detailed Implementation

[0027] To provide a further understanding of the purpose, structure, features, and functions of the present invention, detailed descriptions are provided below with reference to specific embodiments. Example 1:

[0028] Loading: An N-type undoped germanium single crystal seed is loaded into the AB section of a graphite boat. The grade is GeO2-05 high-purity germanium dioxide, and the amount is 5KG. The seed is placed into the BC section of the graphite boat, and the graphite boat containing the material is placed in a self-made "reduction-purification integrated device".

[0029] Segmented hydrogen reduction: Open the inlet valve 7 and the outlet valve 8, and introduce nitrogen into the device through the inlet 5 for 10 minutes; then stop introducing nitrogen and introduce high-purity hydrogen into the device; turn on the resistance heater to heat the BC section of the graphite boat 4, and introduce high-purity hydrogen at a flow rate of 1500 L / h. The first stage of heating involves raising the temperature to 550℃ and holding it there for 4 hours; the second stage involves raising the temperature to 680℃ and holding it there for 6 hours; the third stage involves raising the temperature to 780℃ and holding it there for 6 hours; and the fourth stage involves raising the temperature to 1050℃ and holding it there for 3 hours.

[0030] Heating device switching: Reduce the flow rate of high-purity hydrogen to 500 L / h, turn off the resistance heater 2, and move it to the rear of the furnace body 1; after all the germanium in the graphite boat 4 has condensed into a solid, move the high-frequency induction coil 3 horizontally to a position on the same vertical plane as point B.

[0031] Integrated purification of zone melting and crystal pulling: The heating power of the high-frequency induction coil 3 is set to control the melting zone width of the germanium ingot in the graphite boat 4 to 4cm. The speed of the high-frequency induction coil 3 from moving horizontally and uniformly to ...

[0032] Shutdown and discharge: When the integrated reduction-purification unit cools down to 400°C, hydrogen is turned off and nitrogen is introduced. When the temperature continues to drop to 140°C, nitrogen is stopped. When the temperature drops to 35°C, the integrated reduction-purification unit is turned on, and germanium ingots are obtained from the graphite boat inside the unit. After testing, qualified parts are cut off and sold as zone-melted germanium ingots after conventional surface treatment. Unqualified germanium ingots can be used as raw materials for the production of zone-melted germanium ingots for further purification.

[0033] In this embodiment: Qualified germanium ingot yield = (actual mass of qualified germanium ingots ÷ total mass of germanium metal theoretically achievable from inputting high-purity germanium dioxide) × 100%; High-purity germanium dioxide (GeO2-05), input mass 5.0 kg; According to the reduction reaction equation GeO2 + 2H2 = Ge + 2H2O, the molar ratio of GeO2 to Ge is 1:1 (1 mol of GeO2 can be completely reduced to produce 1 mol of Ge). Therefore, the theoretical mass of Ge produced is calculated using the "mass ratio conversion". Mass ratio of Ge to GeO2: Mass ratio = Ge atomic weight ÷ GeO2 molecular weight = 72.64 ÷ 104.64 ≈ 0.694; Theoretical total output Ge mass = input GeO2 mass × mass ratio = 5.0 kg × 0.694 = 3.47 kg; In the self-made reduction-purification integrated device of the present invention, the device is a closed structure, the gas flow rate during the reduction process is stable (1500L / h), there is no material splashing loss, and the germanium liquid is completely condensed after standing (30min). Therefore, the material loss in the reduction stage is ignored, and the theoretical total output mass is the total germanium ingot mass obtained after actual reduction (3.47kg). According to the test results, in this embodiment, the weight of the qualified germanium ingot is 2.83 kg. The yield of qualified germanium ingots is calculated as follows: (2.83 ÷ 3.47) × 100% =0.816 (rounded to three decimal places) =81.6%.

[0034] Finally, in this embodiment, the final yield of zone-melted germanium ingots is 81.6%. Example 2:

[0035] 1) Loading: Same as in Example 1.

[0036] 2) Segmented hydrogen reduction: Nitrogen gas was introduced for 25 minutes to purge air; high-purity hydrogen gas was introduced at a flow rate of 5000 L / h; the heating parameters were as follows: first stage at 650℃ for 2 hours, second stage at 750℃ for 2 hours, third stage at 850℃ for 2 hours, and fourth stage at 1150℃ for 1 hour.

[0037] 3) Switching heating devices: Reduce the flow rate of high-purity hydrogen to 1200 L / h, and perform the remaining operations as in Example 1.

[0038] 4) Integrated purification of zone melting and crystal pulling: The width of the molten zone is controlled at 2cm, the horizontal running speed of the coil is 20cm / h, and the purification cycle is repeated 4 times.

[0039] 5) Shutdown and discharge of materials: When the device cools down to 350°C, the hydrogen gas is turned off and nitrogen gas is introduced. When the temperature drops to 150°C, the nitrogen gas supply is stopped. After the temperature drops to 50°C, the germanium ingot is removed.

[0040] In this embodiment: Qualified germanium ingot yield = (actual mass of qualified germanium ingots ÷ total mass of germanium metal theoretically achievable from inputting high-purity germanium dioxide) × 100%; High-purity germanium dioxide (GeO2-05), input mass 5.0 kg; The gas flow rate during the reduction process is stable (1200L / h), with no material splashing loss, and the germanium liquid is completely condensed after standing (30min). Therefore, the material loss during the reduction stage can be ignored, and the theoretical total output mass is the same as the total germanium ingot mass obtained after actual reduction (3.47kg). According to the test results, in this embodiment, the weight of the qualified germanium ingot is 3.06 kg. The yield of qualified germanium ingots is calculated as follows: (3.06 ÷ 3.47) × 100% =0.882 (rounded to three decimal places) =88.2%.

[0041] Finally, in this embodiment, the final yield of zone-melted germanium ingots is 88.2%. Example 3:

[0042] 1) Loading: Same as in Example 1.

[0043] 2) Segmented hydrogen reduction: Argon gas was introduced for 20 minutes to purge the air; high-purity hydrogen gas was introduced at a flow rate of 3000 L / h; the heating parameters were as follows: first stage at 620℃ for 3 hours, second stage at 710℃ for 4 hours, third stage at 830℃ for 3 hours, and fourth stage at 1100℃ for 2 hours.

[0044] 3) Switching heating devices: Reduce the flow rate of high-purity hydrogen to 800 L / h, and perform the remaining operations as in Example 1.

[0045] 4) Integrated purification of zone melting and crystal pulling: The width of the melting zone is controlled at 3cm, the horizontal running speed of the coil is 30cm / h, and the purification cycle is repeated 3 times.

[0046] 5) Shutdown and discharge of materials: When the device cools down to 350°C, the hydrogen gas is turned off and the argon gas is introduced. When the temperature drops to 130°C, the argon gas is stopped. After the temperature drops to 30°C, the germanium ingot is removed.

[0047] In this embodiment: Qualified germanium ingot yield = (actual mass of qualified germanium ingots ÷ total mass of germanium metal theoretically achievable from inputting high-purity germanium dioxide) × 100%; High-purity germanium dioxide (GeO2-05), input mass 5.0 kg; The gas flow rate during the reduction process is stable (1200L / h), with no material splashing loss, and the germanium liquid is completely condensed after standing (30min). Therefore, the material loss during the reduction stage can be ignored, and the theoretical total output mass is the same as the total germanium ingot mass obtained after actual reduction (3.47kg). According to the test results, in this embodiment, the weight of the qualified germanium ingot is 2.9 kg. The yield of qualified germanium ingots is calculated as follows: (2.9 ÷ 3.47) × 100% =0.836 (rounded to three decimal places) =83.6%.

[0048] Finally, in this embodiment, the final yield of zone-melted germanium ingots is 88.2%.

[0049] In summary: Under the same raw materials and basic process conditions, the more purification cycles, the more thorough the impurity removal: Example 2 (4 cycles) yield 88.2% > Example 3 (3 cycles) 83.7% > Example 1 (2 cycles) 81.6%. The synergistic effect of multiple cycles of zone melting and crystal pulling can continuously discharge impurities to the end of the melting zone, significantly increasing the proportion of qualified areas in germanium ingots.

[0050] The narrower the melting zone, the more reasonable the local temperature gradient, and the higher the crystal purity: Example 2 (melting zone width 2cm) had the highest yield (88.2%), followed by Example 3 (3cm), and Example 1 (4cm) had the lowest. A narrow melting zone can reduce the diffusion range of impurities during the melting-crystallization process and enhance the impurity removal effect of directional crystallization.

[0051] The slower the high-frequency induction coil moves, the longer the interface interaction time between the molten zone and solid germanium, and the easier it is for impurities to be removed from the molten zone: the yield ranking of Example 2 (20cm / h) > Example 3 (30cm / h) > Example 1 (40cm / h) confirms the process logic that "slow speed is conducive to deep impurity removal".

[0052] The integrated reduction, zone melting, and crystal pulling technology of this invention can achieve a stable yield of ≥81.6% of qualified germanium ingots by precisely controlling core parameters such as purification cycle, melting zone width, and coil moving speed. The product quality is superior to that of traditional processes. Moreover, the process parameters and product quality have a clear quantitative relationship, which facilitates industrial-scale production and completely solves the technical pain points of traditional processes such as "low efficiency, high energy consumption, and low pass rate".

[0053] The present invention has been described in the above-described embodiments; however, these embodiments are merely examples for implementing the present invention. It must be noted that the disclosed embodiments do not limit the scope of the present invention. Conversely, any modifications and refinements made without departing from the spirit and scope of the present invention are within the scope of patent protection of the present invention.

Claims

1. A method for preparing and purifying germanium ingots based on an integrated reduction, zone melting, and crystal pulling technology, characterized in that: The specific steps of the method are as follows: S1: Pre-treatment of loading: Germanium single crystal seed crystals are loaded into the AB section of the graphite boat, high-purity germanium dioxide is placed into the BC section of the graphite boat, and the graphite boat containing the materials is placed in a self-made reduction-purification integrated device. The graphite boat is the core high-temperature resistant molding carrier that supports the germanium ingot; The AB segment of the graphite boat refers to the continuous segment from point A to point B on the graphite boat; the BC segment refers to the continuous segment from point B to point C on the graphite boat; where point B is the core point where the melting zone initially forms, and point C is the termination point of the horizontal movement of the melting zone. The AB and BC segments are two carrier segments on the graphite boat divided along the direction of movement of the melting zone, and are the main carrier areas for placing germanium ingots and completing zone melting crystal pulling and purification. S2: Segmented controllable hydrogen reduction: Open the inlet valve and the outlet valve, and introduce inert gas into the device for a period of time through the inlet to purge the air inside the device; stop introducing inert gas and introduce high-purity hydrogen into the device. The resistance heater is turned on to heat the BC section of the graphite boat. The first stage of heating raises the temperature to the set temperature and then holds it. The second stage of heating raises the temperature to the set temperature and then holds it. The third stage of heating raises the temperature to the set temperature and then holds it. The fourth stage of heating raises the temperature to the set temperature and then holds it. S3: Switch heating device: Reduce the flow rate of high-purity hydrogen, turn off the resistance heater, and move it to the rear of the furnace. After all the germanium in the graphite boat has condensed into a solid, move the high-frequency induction coil horizontally to a position on the same vertical plane as point B. S4: Integrated purification of zone melting and crystal pulling: The width of the germanium ingot melting zone inside the graphite boat is controlled by setting the heating power of the high-frequency induction coil, and the impurity removal effect of zone melting and crystal pulling is controlled by setting its horizontal running speed. The high-frequency induction coil first heats the area near point B of the graphite boat with high-frequency induction, causing germanium to melt and form a molten zone while germanium remains solid on both sides of the molten zone. Then, it moves horizontally and uniformly from the vertical plane of point B to the vertical plane of point C, causing the melting zone of germanium to move synchronously and uniformly. Subsequently, the high-frequency induction coil stops heating and automatically returns to the initial position of the vertical plane of point B, completing one zone melting and crystal pulling purification cycle. By repeating this cycle a set number of times, the zone melting and crystal pulling purification of the germanium ingot can be completed in this round. S5: Shutdown and discharge: After initial cooling within the integrated reduction-purification unit, hydrogen is shut off and inert gas is introduced. The unit continues to cool naturally to no more than 150°C before stopping the inert gas supply. The inlet and outlet valves are then closed, and the furnace continues to cool naturally to an even lower temperature range before the integrated reduction-purification unit is opened. Germanium ingots can be obtained from the graphite boat within the unit. After testing, qualified portions are cut off and, after routine surface treatment, sold as zone-melted germanium ingots. Unqualified germanium ingots can be used as raw materials for further purification in the production of zone-melted germanium ingots.

2. The method for preparing and purifying germanium ingots based on the integrated reduction, zone melting, and crystal pulling technology as described in claim 1, characterized in that: In step S2, the inert gas introduced is nitrogen or argon, and the inert gas is introduced for 10-30 minutes. Then, the inert gas is stopped, and high-purity hydrogen is introduced at a flow rate of 1000-6000 L / h. In the first stage, the temperature is raised to 550-680℃ and held for 2-4 hours. In the second stage, the temperature is raised to 680-750℃ and held for 2-6 hours. In the third stage, the temperature is raised to 750-890℃ and held for 2-6 hours. In the fourth stage, the temperature is raised to 1000-1150℃ and held for 1-3 hours.

3. The method for preparing and purifying germanium ingots based on the integrated reduction, zone melting, and crystal pulling technology as described in claim 1, characterized in that: In step S4, the heating power of the high-frequency induction coil is adjusted to control the width of the melting zone to 2-4 cm, and the speed of the high-frequency induction coil from moving horizontally and uniformly in the same vertical plane as point B to moving in the same vertical plane as point C is controlled to be 20-40 cm / h. The number of cycles for zone melting and crystal pulling purification is set to 2-5 times.

4. The method for preparing and purifying germanium ingots based on the integrated reduction, zone melting, and crystal pulling technology as described in claim 1, characterized in that: In step S5, when the integrated reduction-purification device cools down to no more than 450°C, the hydrogen gas is turned off and nitrogen or argon gas is introduced. When the temperature continues to drop to no more than 150°C, the nitrogen or argon gas is stopped. After cooling down to no more than 50°C, the integrated reduction-purification device is turned on, and germanium ingots can be obtained from the graphite boat inside the device.

5. The method for preparing and purifying germanium ingots based on the integrated reduction, zone melting, and crystal pulling technology as described in claim 1, characterized in that: In step S1, the germanium single crystal seed crystal used should meet the quality requirements of N-type undoped germanium single crystal in GB / T5238; the high-purity germanium dioxide used should meet the quality requirements of GeO2-05 and above grade high-purity germanium dioxide in YS / T11069.

6. A reduction-purification integrated apparatus for the method of preparing and purifying germanium ingots based on the integrated technology of reduction, zone melting and crystal pulling as described in claim 1, characterized in that: The furnace includes a furnace body (1), a resistance heater (2), a high-frequency induction coil (3), a graphite boat (4), an air inlet (5), and an exhaust port (6). The furnace body (1) is a sealed cavity structure. The graphite boat (4) is horizontally embedded in the central area inside the furnace body (1), and the length direction of the graphite boat (4) is consistent with the axial direction of the furnace body (1). A safety gap of 5-10cm is reserved between the graphite boat (4) and the inner wall of the furnace body (1). The resistance heater (2) and the high-frequency induction coil (3) are respectively movably connected to the side wall of the furnace body (1) through an external translation drive mechanism, and the running trajectory of the translation drive mechanism is parallel to the length direction of the graphite boat (4), so that the resistance heater (2) is translated to the graphite boat. The high-frequency induction coil (3) is moved to the working position corresponding to the same vertical plane as point B of the graphite boat and the entire length of the BC section, and both are located in the avoidance area at the rear of the furnace body when not in working state, and do not interfere with each other; the air inlet (5) and the exhaust outlet (6) are respectively opened on the end walls of the furnace body (1), and both are connected to the sealed cavity of the furnace body (1). The exhaust end of the air inlet (5) extends to the side of the furnace body near the A end of the graphite boat (4), and the air inlet end of the exhaust outlet (6) extends to the side of the furnace body near the C end of the graphite boat (4), forming a gas flow channel along the length of the graphite boat (4); the air inlet valve (7) is provided on the air inlet (5); the exhaust outlet valve (8) is also provided on the exhaust outlet (6).

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