Method for preparing high-purity germanium ingot by vacuum melting ingot casting of reduced germanium powder

Abstract

The invention discloses a method for preparing a high-purity germanium ingot through reduced germanium powder vacuum melting ingot casting. The method comprises the following steps that firstly, a graphite boat is cleaned and charged; step 2, vacuumizing; 3, introducing nitrogen containing 1% of hydrogen; 4, raising the temperature, heating and melting the cast ingot; step 5, cooling is carried out; sixthly, the high-purity nitrogen continues to be introduced till the normal temperature and the normal pressure in the furnace body are recovered; and 7, discharging and taking materials. The high-purity reduced germanium powder is subjected to ingot casting in the vacuum nitrogen protective atmosphere through the high-temperature ingot casting furnace, participation of a large amount of hydrogen is avoided, the production cost and the safety risk are reduced, the production efficiency is improved, and the production cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of rare metal metallurgy, and in particular relates to a method for preparing a high-purity germanium ingot by reducing germanium powder through vacuum melting and ingot casting. Background Art

[0002] The industrial production of high-purity metallic germanium usually requires the germanium concentrate to be subjected to chlorination, distillation, back distillation, rectification purification, hydrolysis, filtration, and drying in a chlorination distillation reactor to obtain high-purity germanium dioxide, and then to high-purity hydrogen reduction to obtain high-purity germanium powder, and then the high-purity germanium powder is melted and cast to obtain high-purity germanium polycrystalline ingots, and then single crystal growth is performed to obtain high-purity germanium single crystals, which are then processed into germanium single wafers for use in different application fields such as solar satellite power supplies, infrared thermal imagers, and high-purity germanium detectors. The ingot casting process of high-purity reduced germanium powder can make the trace impurities therein more evenly distributed throughout the ingot, ensure the consistency and stability of the performance of the germanium material, make the germanium atoms closely combined, increase the density and strength of the germanium material, and improve the reliability of the germanium material. At the same time, some impurities can also be removed to form the required crystal shape, which is convenient for subsequent regional smelting and purification.

[0003] At present, the conventional high-purity reduced germanium powder ingot casting process is to generate high-purity reduced germanium powder after hydrogen is introduced into a horizontally placed tubular reduction furnace to reduce high-purity germanium dioxide (650℃-700℃) placed in a high-purity graphite boat, and then continue to heat up to 1050℃, exceeding the melting point of germanium metal 937℃, so that the reduced germanium powder is melted into liquid germanium metal, and after being kept stable for a period of time, the temperature is slowly cooled to room temperature, and the liquid germanium metal solidifies to obtain a high-purity germanium ingot. The existing technologies all obtain high-purity germanium by improving the zone melting environment, zone melting conditions and raw materials, and do not involve using high-purity reduced germanium powder as raw material to obtain germanium polycrystals through vacuum melting ingot casting. Summary of the invention

[0004] The object of the present invention is to provide a method for producing a high-purity germanium ingot by vacuum melting and casting with high-purity reduced germanium powder as raw material, so as to facilitate subsequent regional smelting and purification.

[0005] In order to solve the above problems, the present invention provides a method for preparing a high-purity germanium ingot by reducing germanium powder and vacuum melting ingot casting, which is characterized by comprising the following steps: The first step is to clean and load the graphite boat; weigh 3000 to 3500g of high-purity reduced germanium powder and put it in a single graphite boat, then horizontally place the graphite boat in the corresponding groove of the fixed graphite boat on the graphite boat bracket, and then slowly place the graphite boat bracket in the vacuum melting ingot furnace, cover the furnace cover, and make the furnace body completely closed and sealed; the vacuum melting ingot furnace consists of a furnace body, a furnace cover, a vacuum pump and a graphite boat bracket; the furnace cover is arranged on the furnace body, the furnace cover is provided with a water circulation pipeline, and the furnace cover is provided with a discharge pipeline and a pressure gauge; the furnace body is a hollow cylinder, a vacuum furnace is arranged inside, the furnace body is provided with an exhaust pipe, and the exhaust pipe is connected to the vacuum pump; a heating resistor belt is arranged around the furnace body and is wound into a corrugated shape; The second step is to vacuum; The third step is to introduce nitrogen containing 1% hydrogen; The fourth step is to heat the molten ingot by heating; first preheating the furnace to 200 to 230°C and keeping it for 40 minutes; then heating to 650 to 680°C at a rate of 6 to 7°C / min and keeping it for 120 minutes; then heating to 750 to 780°C and keeping it for 120 minutes, heating to 900 to 930°C at a rate of 4 to 5°C / min and keeping it for 40 minutes, heating to 1000 to 1030°C at a rate of 4 to 5°C / min, and keeping the constant temperature for 60 minutes to cast the ingot; The fifth step is cooling down. After the ingot casting time is up, the temperature is controlled to drop steadily. When the temperature drops to 800℃ just after the ingot casting, a rapid cooling rate of 5 to 6℃ / min is used, which helps to inhibit the adverse phase change and excessive growth of microstructure under high temperature. During the period of 800℃-500℃, a rate of 2 to 3℃ / min is used, because the phase change of germanium is more sensitive at this stage, and too fast cooling will lead to increased internal stress and the formation of structural defects. When it is below 500℃, a rate of 2℃ / min is used to further reduce the cooling rate, which is conducive to reducing the generation of cracks until the cooling is completed. Step 6: Continue to introduce high-purity nitrogen until the furnace body returns to normal temperature and pressure; Step 7: Take the material out of the furnace.

[0006] Furthermore, the graphite boat is cleaned by placing the high-purity graphite boat in the prepared aqua regia and soaking it for 24 hours, then placing it in deionized water and heating it to boiling, repeating the cleaning 8 to 10 times, and finally placing the graphite boat in a vacuum melting ingot furnace to dry, heating it to a temperature of 1000°C, taking out the graphite boat after cooling, and then wiping it clean with alcohol.

[0007] Furthermore, the vacuum is to open the valve of the exhaust pipe, then open the pressure gauge valve, and then turn on the vacuum pump power switch until the vacuum pressure gauge shows less than 50 Pa and the vacuum degree remains stable for 40 to 45 minutes, then turn off the vacuum pump. This process lasts for about 20 minutes.

[0008] Further, the nitrogen containing 1% hydrogen is introduced by slowly opening the nitrogen pipeline, firstly introducing high-purity nitrogen at a rate of 10 to 20 L / min, maintaining for 30 to 50 minutes, then adjusting the rate to 30 to 40 L / min and maintaining it unchanged, and then maintaining it for 30 to 50 minutes, until the vacuum pressure gauge shows 50000 to 84100 Pa and the vacuum degree is kept stable for 40 minutes, indicating that the nitrogen filling is completed and the vacuum degree meets the requirements, repeating this step 3 times; then introducing high-purity hydrogen at a rate of 3 to 5 L / min and maintaining it for 5 minutes, until the vacuum pressure gauge shows about 50500 to 84940 Pa and the vacuum degree is kept stable for 40 minutes, indicating that a nitrogen atmosphere containing 1% hydrogen is formed. A small amount of hydrogen is filled into the nitrogen to prevent the reduced germanium powder from being oxidized to germanium dioxide by trace oxygen.

[0009] Furthermore, continue to introduce high-purity nitrogen, wait until the furnace body returns to normal temperature and pressure, and after cooling is completed, open the nitrogen pipeline, and introduce high-purity nitrogen at a rate of 25 to 50L / min for about 20 to 30 minutes, until the vacuum pressure gauge shows about 101000Pa, indicating that the pressure in the furnace has returned to normal pressure, and stop introducing gas.

[0010] Furthermore, the process of taking out the materials from the furnace is to wait until the temperature and pressure in the furnace return to normal temperature and pressure, then lift up the furnace cover, take out the support, then take out the graphite boat from the support, and then take out the high-purity germanium ingot from the graphite boat.

[0011] The above-mentioned technical scheme of the present invention has the following beneficial technical effects: high-purity reduced germanium powder is cast in a vacuum nitrogen protective atmosphere through a high-temperature ingot casting furnace, thereby avoiding the participation of a large amount of hydrogen and reducing production costs and safety risks. Since multiple graphite boats can be placed in the vacuum furnace body for each operation, the processing capacity reaches 120 kilograms, which correspondingly reduces the time required for production, and the output of a single furnace is also greatly improved, thereby improving production efficiency and reducing production costs. The power of the device of the present invention is controllable and can be adjusted in real time as needed. The power consumption required in the production process is reduced, and it helps to reduce the problem of uneven product performance caused by temperature differences. The device of the present invention is placed vertically, which is conducive to thorough vacuuming and shortening the process time. After the heating is completed, the nitrogen flow rate is reduced to suppress the heat taken away, while saving the amount of high-purity nitrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a flow chart of a method for preparing a high-purity germanium ingot by reducing germanium powder and vacuum melting ingot casting; Figure 2 This is a diagram of the structure of a vacuum melting ingot furnace; Figure 3 It is a top view of the graphite boat support.

[0013] Reference numerals: 1: furnace body; 2: furnace cover; 3: graphite boat support; 4: water circulation pipeline; 5: discharge pipeline; 6: pressure gauge; 7: vacuum furnace; 8: exhaust pipe; 9: heating resistor belt; 10: graphite boat. DETAILED DESCRIPTION

[0014] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0015] like Figure 1 As shown, a method for preparing a high-purity germanium ingot by reducing germanium powder and vacuum melting ingot casting is provided, characterized in that it comprises the following steps: The first step is to clean and load the graphite boat; soak the high-purity graphite boat in the prepared aqua regia for 24 hours, then place it in deionized water and heat it to boiling, repeat the cleaning 8 to 10 times, and finally place the graphite boat in a vacuum melting ingot furnace to dry, heat it to 1000°C, take out the graphite boat after cooling, and wipe it clean with alcohol. Weigh 3000 to 3500g of high-purity reduced germanium powder and put it in a single graphite boat, then place the graphite boat horizontally in the corresponding groove of the fixed graphite boat on the graphite boat bracket, and then slowly place the graphite boat bracket in the vacuum melting ingot furnace, cover the furnace cover, and make the furnace body completely closed and sealed; Figure 2 and Figure 3 As shown, the vacuum melting ingot furnace consists of a furnace body 1, a furnace cover 2, a vacuum pump and a graphite boat support 3; the furnace cover 2 is arranged on the furnace body 1, and the furnace cover 2 is provided with a water circulation pipeline 4, and the furnace cover 2 is provided with a discharge pipeline 5 and a pressure gauge 6; the furnace body 1 is a hollow cylinder, and a vacuum furnace chamber 7 is arranged inside, and the furnace body 1 is provided with an exhaust pipe 8, and the exhaust pipe 8 is connected to the vacuum pump; a heating resistor belt 9 is arranged around the furnace body and is wound into a corrugated shape; The second step is to evacuate the air; open the valve of the exhaust pipe, then open the valve of the pressure gauge, and then turn on the power switch of the vacuum pump. When the vacuum pressure gauge shows less than 50 Pa and the vacuum degree remains stable for 40 to 45 minutes, turn off the vacuum pump. This process lasts for about 20 minutes. The third step is to introduce nitrogen containing 1% hydrogen; slowly open the nitrogen pipeline, first introduce high-purity nitrogen at a rate of 10 to 20L / min, maintain for 30 to 50min, then adjust the rate to 30 to 40L / min and keep it unchanged, and then maintain it for 30 to 50min, until the vacuum pressure gauge shows 50000 to 84100Pa and the vacuum degree remains stable for 40min, indicating that the nitrogen filling is completed and the vacuum degree meets the requirements, repeat this step 3 times; then introduce high-purity hydrogen at a rate of 3 to 5L / min and maintain for 5min, until the vacuum pressure gauge shows about 50500 to 84940Pa and the vacuum degree remains stable for 40min, indicating that a nitrogen atmosphere containing 1% hydrogen is formed. Filling a small amount of hydrogen into the nitrogen can prevent the reduced germanium powder from being oxidized to germanium dioxide by trace oxygen; The fourth step is to heat the molten ingot by heating; first preheating the furnace to 200 to 230°C and keeping it for 40 minutes; then heating to 650 to 680°C at a rate of 6 to 7°C / min and keeping it for 120 minutes; then heating to 750 to 780°C and keeping it for 120 minutes, heating to 900 to 930°C at a rate of 4 to 5°C / min and keeping it for 40 minutes, heating to 1000 to 1030°C at a rate of 4 to 5°C / min, and keeping the constant temperature for 60 minutes to cast the ingot; The fifth step is cooling down. After the ingot casting time is up, the temperature is controlled to drop steadily. When the temperature drops to 800℃ just after the ingot casting, a rapid cooling rate of 5 to 6℃ / min is used, which helps to inhibit the adverse phase change and excessive growth of microstructure under high temperature. During the period of 800℃-500℃, a rate of 2 to 3℃ / min is used, because the phase change of germanium is more sensitive at this stage, and too fast cooling will lead to increased internal stress and the formation of structural defects. When it is below 500℃, a rate of 2℃ / min is used to further reduce the cooling rate, which is conducive to reducing the generation of cracks until the cooling is completed. Step 6: Continue to introduce high-purity nitrogen until the furnace body returns to normal temperature and pressure; after cooling, open the nitrogen pipeline and introduce high-purity nitrogen at a rate of 25 to 50 L / min for about 20 to 30 minutes, until the vacuum pressure gauge shows about 101000 Pa, indicating that the pressure in the furnace has returned to normal pressure, and stop introducing gas; The seventh step is to take out the materials from the furnace; after the temperature and pressure in the furnace return to normal temperature and pressure, lift the furnace cover, take out the bracket, then take out the graphite boat from the bracket, and then take out the high-purity germanium ingot from the graphite boat.

[0016] A method for casting high-purity reduced germanium powder using a vacuum melting ingot casting furnace. The following Table 1 compares the ingot casting method of the present invention with that of a conventional horizontal atmospheric pressure tubular quartz reduction furnace: Table 1 Comparison between vacuum furnace melting ingot casting method and conventional quartz tubular reduction ingot casting method Method for reducing germanium powder ingot Vacuum ingot casting furnace melting ingot casting method Quartz tubular reduction furnace ingot casting method Use equipment Vacuum Melting Ingot Furnace Quartz tubular reduction furnace Furnace placement Vertical placement Horizontal placement Single furnace boat loading capacity 40 boats are placed in a single furnace, each boat is loaded with 3 kg of high-purity reduced germanium powder, Ge≥99.999% One boat is placed in each furnace, which is loaded with 2.5 high purity germanium dioxide Single furnace high purity germanium ingot output (kg) 120 1.7 Single furnace single time consumption (h) 8, ingots 24. Reduction + Ingot Ingot casting equipment power (KW) 200 (adjustable) 30 (adjustable) Design maximum temperature (℃) 1100 1100 Use gas High purity nitrogen (purity ≥ 99.999%) + 1% high purity hydrogen High-purity hydrogen (purity ≥ 99.999%) Cooling method Real-time temperature control and cooling Natural cooling Ingot casting furnace lining Ceramic fiber high voltage module High temperature refractory materials, asbestos Heating elements 0Cr25AL5 resistance belt Conventional resistance wire Embodiment 1: A method for vacuum casting high-purity reduced germanium powder to obtain a high-purity germanium ingot, the specific steps are as follows: The first step is to clean and load the graphite boat: First, soak the high-purity graphite boat in the prepared aqua regia (nitric acid: hydrochloric acid = 1:3) for 24 hours, then place it in deionized water and heat it to boiling. Repeat this step 8 times. Finally, place the graphite boat in a vacuum furnace to dry it at a heating temperature of about 1000 °C. After cooling, take out the graphite boat and wipe it clean with alcohol.

[0017] Weigh 3000 g of high-purity reduced germanium powder and place it in a single graphite boat, and spread it evenly to avoid accumulation. After filling the 40 graphite boats of the entire furnace, place the graphite boat horizontally in the corresponding groove of the fixed graphite boat on the bracket, and then slowly place the bracket in the vacuum furnace tank, press the operation button to control the furnace cover to slowly descend until it is completely closed and sealed with the furnace body.

[0018] The second step is to vacuum: After the furnace cover is completely lowered and sealed, open the exhaust valve. Before starting to evacuate the vacuum, check whether the vacuum pump is in normal condition. Then open the pressure gauge valve and then turn on the vacuum pump power switch. Wait until the vacuum pressure gauge shows less than 50 Pa and the vacuum remains stable for 45 minutes, indicating that the vacuum degree has met the requirements. Turn off the vacuum pump. This process lasts for about 20 minutes.

[0019] The third step is to introduce nitrogen containing 1% hydrogen: Slowly open the nitrogen pipeline, first introduce high-purity nitrogen at a rate of 20 L / min, maintain for 30 minutes, then adjust the rate to 30 L / min and keep it constant, and then maintain it for 30 minutes, until the vacuum pressure gauge shows 50000Pa and the vacuum degree remains stable for 40 minutes, indicating that the nitrogen filling is completed and the vacuum degree meets the requirements, repeat this step 3 times. Then introduce high-purity hydrogen at a rate of 3 L / min and maintain for 5 minutes, until the vacuum pressure gauge shows about 50500 Pa and the vacuum degree remains stable for 40 minutes, indicating that a vacuum high-purity nitrogen (containing 1% high-purity hydrogen) atmosphere environment is formed. A small amount of hydrogen is filled in the nitrogen to prevent the reduced germanium powder from being oxidized to germanium dioxide by trace oxygen.

[0020] Step 4: Heat up and melt the ingot: First, preheat treatment is carried out to raise the temperature in the furnace to 200 ℃ and maintain it for 40 min to reduce thermal stress; then the temperature is raised to 650 ℃ at a rate of 6 ℃ / min and maintained for 120 min; then the temperature is raised to 750 ℃ ​​and maintained for 120 min, and then the temperature is raised to 900 ℃ at a rate of 4 ℃ / min and maintained for 40 min, and then the temperature is raised to 1000 ℃ at a rate of 4 ℃ / min, and the temperature is maintained at 1000 ℃ for 60 min for ingot casting.

[0021] Step 5: Cooling down: After the ingot casting time is up, the temperature is controlled to drop steadily; in the 1000℃-800℃ range just after the ingot casting is completed, a rapid cooling rate of 5℃ / min is used, which helps to inhibit adverse phase changes and excessive growth of microstructures at high temperatures; during the 800℃-500℃ period, the cooling rate needs to be slowed down to 2℃ / min, because the phase change of germanium is more sensitive at this stage, and too fast cooling will lead to increased internal stress and the formation of structural defects; below 500℃, a rate of 2℃ / min is used to further reduce the cooling rate, which is conducive to reducing the occurrence of cracks.

[0022] Step 6: Continue to introduce high-purity nitrogen until the furnace returns to normal temperature and pressure: After cooling, open the nitrogen pipeline and introduce high-purity nitrogen at a rate of 50 L / min for about 30 minutes, until the vacuum pressure gauge shows about 101000 Pa, indicating that the pressure in the furnace has returned to normal pressure, and stop introducing gas. After stopping the ventilation, wait for a while to stabilize the internal pressure and temperature, and when the temperature drops to 30 ℃ and reaches normal temperature and pressure, prepare to open the furnace and discharge the materials.

[0023] Step 7: Take the material out of the furnace: After the temperature and pressure in the furnace return to normal temperature and pressure, press the operation button to raise the furnace cover, slowly take out the bracket, then take out the graphite boat from the bracket, and then take out the high-purity germanium ingot from the graphite boat and transfer it to the high-purity zone melting graphite boat for subsequent regional melting and purification.

[0024] Embodiment 2: A method for obtaining high-purity germanium polycrystal by vacuum casting high-purity reduced germanium powder, wherein the specific steps are as follows: The first step is to clean and load the graphite boat: First, soak the high-purity graphite boat in the prepared aqua regia (nitric acid: hydrochloric acid = 1:3) for 24 hours, then place it in deionized water and heat it to boiling. Repeat this step 10 times. Finally, place the graphite boat in a vacuum furnace to dry it at a heating temperature of 1000 °C. After cooling, take out the graphite boat and wipe it clean with alcohol.

[0025] Weigh 3500 g of high-purity reduced germanium powder and place it in a single graphite boat, and spread it evenly to avoid accumulation. After filling the 40 graphite boats of the entire furnace, place the graphite boat horizontally in the corresponding groove of the fixed graphite boat on the bracket, and then slowly place the bracket in the vacuum furnace tank. Press the operation button to control the furnace cover to slowly descend until it is completely closed and sealed with the furnace body.

[0026] The second step is to vacuum: After the furnace cover is completely lowered and sealed, open the exhaust valve. Before starting to evacuate the vacuum, check whether the vacuum pump is in normal condition. Then open the pressure gauge valve and then turn on the vacuum pump power switch. Wait until the vacuum pressure gauge shows less than 50 Pa and the vacuum remains stable for 40 minutes, indicating that the vacuum degree has met the requirements. Turn off the vacuum pump. This process lasts for about 20 minutes.

[0027] The third step is to introduce nitrogen containing 1% hydrogen: Slowly open the nitrogen pipeline, first introduce high-purity nitrogen at a rate of 10 L / min, maintain for 50 min, then adjust the rate to 40 L / min and keep it constant, and then maintain it for 50 min, until the vacuum pressure gauge shows 84100 Pa and the vacuum degree remains stable for 40 min, indicating that the nitrogen filling is completed and the vacuum degree meets the requirements, repeat this step 3 times. Then introduce high-purity hydrogen at a rate of 5 L / min and maintain for 5 min, until the vacuum pressure gauge shows about 84940 Pa and the vacuum degree remains stable for 40 min, indicating that a vacuum high-purity nitrogen (containing 1% high-purity hydrogen) atmosphere environment is formed. A small amount of hydrogen is filled in the nitrogen to prevent the reduced germanium powder from being oxidized to germanium dioxide by trace oxygen.

[0028] Step 4: Heat up and melt the ingot: First, preheat treatment is carried out to raise the temperature in the furnace to 230 ℃ and maintain it for 40 min to reduce thermal stress; then the temperature is raised to 680 ℃ at a rate of 7 ℃ / min and maintained for 120 min; then the temperature is raised to 780 ℃ and maintained for 120 min, and then the temperature is raised to 930 ℃ at a rate of 5 ℃ / min and maintained for 40 min, and then the temperature is raised to 1030 ℃ at a rate of 5 ℃ / min, and the temperature is maintained at 1030 ℃ for 60 min for ingot casting.

[0029] Step 5: Cooling down: After the ingot casting time is up, the temperature is controlled to drop steadily; at 1030℃-800℃ just after the ingot casting is completed, a rapid cooling rate of 6℃ / min is used, which helps to inhibit adverse phase changes and excessive growth of microstructures at high temperatures; at 800℃-500℃, the cooling rate needs to be slowed down to 3℃ / min, because the phase change of germanium is more sensitive at this stage, and too fast cooling will lead to increased internal stress and the formation of structural defects; below 500℃, a rate of 2℃ / min is used to further reduce the cooling rate, which is conducive to reducing the occurrence of cracks.

[0030] Step 6: Continue to introduce high-purity nitrogen until the furnace returns to normal temperature and pressure: After cooling, open the nitrogen pipeline and introduce high-purity nitrogen at a rate of 25 L / min for about 20 minutes, until the vacuum pressure gauge shows about 101000 Pa, indicating that the pressure in the furnace has returned to normal pressure, and stop introducing gas. After stopping the ventilation, wait for a while to stabilize the internal pressure and temperature, and when the temperature drops to 30 ℃ and reaches normal temperature and pressure, prepare to open the furnace and discharge the materials.

[0031] Step 7: Take the material out of the furnace: After the temperature and pressure in the furnace return to normal temperature and pressure, press the operation button to raise the furnace cover, slowly take out the bracket, then take out the graphite boat from the bracket, and then take out the high-purity germanium ingot from the graphite boat and transfer it to the high-purity zone melting graphite boat for subsequent regional melting and purification.

[0032] It should be understood that the above specific embodiments of the present invention are only used to illustrate or explain the principles of the present invention, and do not constitute a limitation of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. In addition, the appended claims of the present invention are intended to cover all changes and modifications that fall within the scope and boundaries of the appended claims, or the equivalent forms of such scope and boundaries.

Claims

1. A method for preparing a high-purity germanium ingot by reducing germanium powder and vacuum melting ingot casting, characterized in that: The following steps are involved: The first step is the cleaning and loading of the graphite boat; Weigh 3000 to 3500g of high-purity reduced germanium powder and put it in a single graphite boat, then horizontally place the graphite boat in the corresponding groove of the fixed graphite boat on the graphite boat bracket, then slowly place the graphite boat bracket in a vacuum melting ingot casting furnace, cover the furnace cover, and make the furnace body completely closed and sealed; the vacuum melting ingot casting furnace consists of a furnace body, a furnace cover, a vacuum pump and a graphite boat bracket; the furnace cover is arranged on the furnace body, the furnace cover is provided with a water circulation pipeline, and the furnace cover is provided with a discharge pipeline and a pressure gauge; the furnace body is a hollow cylinder, a vacuum furnace chamber is arranged inside, the furnace body is provided with an exhaust pipe, and the exhaust pipe is connected to the vacuum pump; a heating resistor belt is arranged around the furnace body and is wound into a corrugated shape; The second step is to vacuum; The third step is to introduce nitrogen containing 1% hydrogen; The fourth step is to heat the molten ingot by heating; first preheating the furnace to 200 to 230°C and keeping it for 40 minutes; then heating to 650 to 680°C at a rate of 6 to 7°C / min and keeping it for 120 minutes; then heating to 750 to 780°C and keeping it for 120 minutes, heating to 900 to 930°C at a rate of 4 to 5°C / min and keeping it for 40 minutes, heating to 1000 to 1030°C at a rate of 4 to 5°C / min, and keeping the constant temperature for 60 minutes to cast the ingot; Step 5: Cooling down. After the ingot casting time is up, control the temperature to drop steadily. When the temperature drops to 800℃ just after the ingot casting, use 5 to 6℃ / min to quickly cool down. During the period of 800℃-500℃, use 2 to 3℃ / min. When the temperature is below 500℃, use 2℃ / min until the cooling is completed. Step 6: Continue to introduce high-purity nitrogen until the furnace body returns to normal temperature and pressure; Step 7: Take the material out of the furnace.

2. The method for preparing a high-purity germanium ingot by vacuum melting and ingot casting of reduced germanium powder according to claim 1, characterized in that: The graphite boat cleaning is to place the high-purity graphite boat in the prepared aqua regia and soak it for 24 hours, then place it in deionized water and heat it to boiling, repeat the cleaning 8 to 10 times, and finally place the graphite boat in a vacuum melting ingot furnace to dry, heat it to a temperature of 1000° C., take out the graphite boat after cooling, and then wipe it clean with alcohol.

3. The method for preparing a high-purity germanium ingot by vacuum melting and ingot casting of reduced germanium powder according to claim 1, characterized in that: The vacuuming is to open the valve of the exhaust pipe, then open the pressure gauge valve, and then turn on the vacuum pump power switch until the vacuum pressure gauge shows less than 50 Pa and the vacuum degree remains stable for 40 to 45 minutes, and then turn off the vacuum pump.

4. The method for preparing a high-purity germanium ingot by vacuum melting and ingot casting of reduced germanium powder according to claim 1, characterized in that: The method of introducing nitrogen containing 1% hydrogen is to slowly open the nitrogen pipeline, first introduce high-purity nitrogen at a rate of 10 to 20 L / min, maintain it for 30 to 50 minutes, then adjust the rate to 30 to 40 L / min and keep it unchanged, and then maintain it for 30 to 50 minutes, until the vacuum pressure gauge displays 50000 to 84100 Pa and the vacuum degree is kept stable for 40 minutes, indicating that the nitrogen filling is completed and the vacuum degree meets the requirements; then introduce high-purity hydrogen at a rate of 3 to 5 L / min and maintain it for 5 minutes, until the vacuum pressure gauge displays about 50500 to 84940 Pa and the vacuum degree is kept stable for 40 minutes, indicating that a nitrogen atmosphere environment containing 1% hydrogen is formed.

5. The method for preparing a high-purity germanium ingot by vacuum melting and ingot casting of reduced germanium powder according to claim 1, characterized in that: Continue to introduce high-purity nitrogen until the furnace body returns to normal temperature and pressure. After cooling, open the nitrogen pipeline and introduce high-purity nitrogen at a rate of 25 to 50 L / min for about 20 to 30 minutes until the vacuum pressure gauge shows about 101000 Pa, indicating that the pressure in the furnace has returned to normal pressure, and stop introducing gas.

6. The method for preparing a high-purity germanium ingot by vacuum melting and ingot casting of reduced germanium powder according to claim 1, characterized in that: The process of taking out the materials from the furnace is to raise the furnace cover, take out the support, take out the graphite boat from the support, and then take out the high-purity germanium ingot from the graphite boat after the temperature and pressure in the furnace return to normal temperature and pressure.

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