Gallium oxide crystal with low impurity content and growth method thereof

Abstract

The invention discloses a gallium oxide crystal with low impurity content and a growth method thereof, and belongs to the technical field of gallium oxide crystal growth. The total impurity density in the gallium oxide crystal is less than or equal to 150ppm; wherein the total precious metal impurity density is less than or equal to 100 ppm; the impurity density of aluminum is less than or equal to 30ppm; the impurity density of zirconium is less than or equal to 30ppm; the impurity density of iron is less than or equal to 1ppm. The gallium oxide crystal is low in impurity content, and the quality and uniformity of the gallium oxide crystal can be effectively improved.

Description

Technical Field

[0001] This application relates to a gallium oxide crystal with low impurity content and its growth method, belonging to the field of gallium oxide crystal growth technology. Background Technology

[0002] Gallium oxide (GaO) crystal growth requires a high-temperature environment, approximately 1800°C. During growth, the GaO raw material must be heated to above 1790°C to melt it and maintained stable within a specific temperature range for a period. Subsequently, the temperature is slowly reduced to achieve crystal growth. The entire process demands stringent requirements for temperature stability and uniformity. The crucible, as the core carrier for melting the GaO raw material, crystal nucleation, and growth, directly determines the crystal's growth quality, size, and performance at its temperature. Therefore, crucible temperature control is a critical step in the GaO crystal growth process.

[0003] In existing gallium oxide crystal growth technologies, crucibles are mostly made of iridium, rhodium, iridium-rhodium alloys, or alumina-based composite materials. Although these materials can withstand the high temperatures required for crystal growth, they have high thermal conductivity, and heat is easily dissipated rapidly through the crucible walls, leading to the following technical problems: 1. Rapid heat loss from the crucible leads to uneven temperature distribution within the furnace, creating significant temperature gradients both vertically and horizontally within and outside the crucible. On one hand, excessive temperature gradients can disrupt the convection flow of the gallium oxide melt, damaging the stable solid-liquid interface required for crystal growth. This results in defects such as dissociation cracks and dislocations in the crystal, reducing crystal quality and potentially preventing the formation of a complete single crystal. On the other hand, uneven temperature distribution leads to inconsistent crystal growth rates, making it difficult to produce large-size, highly uniform gallium oxide single crystals, thus limiting its application in high-power devices.

[0004] 2. Ineffective heat loss significantly increases the energy consumption of the heating system. To maintain a stable high temperature of the gallium oxide melt in the crucible, the heating mechanism (such as a medium- or high-frequency induction coil or a resistance heater) needs to continuously output a large amount of energy to compensate for the heat loss from the crucible. This not only increases the production cost of crystal growth but may also lead to faster wear and tear on the heating elements due to excessive heating power, shortening the equipment's lifespan and increasing production and maintenance costs.

[0005] 3. Rapid fluctuations in crucible surface temperature exacerbate the volatilization and compositional changes of gallium oxide melt. Gallium oxide is highly volatile at high temperatures. If the crucible temperature is unstable, it will lead to an imbalance in the composition of the melt surface, which in turn affects the stoichiometry of the crystal, resulting in impurities and defects. At the same time, the volatilized gallium oxide vapor may also adhere to furnace components, contaminating the equipment and further affecting the stability of the crystal growth environment, reducing the consistency of crystal performance.

[0006] 4. During the cooling stage after crystal growth, excessive heat loss from the crucible can lead to significant thermal stress within the crystal, further increasing the risk of cracking. This is especially true for large-size gallium oxide crystals, which have poor thermal conductivity and struggle to release thermal stress quickly, making them highly susceptible to breakage during cooling and resulting in a substantial decrease in production yield.

[0007] Therefore, we now continue with a gallium oxide crystal growth method with low impurity content to reduce the impurity content and crystal defects in gallium oxide crystals. Summary of the Invention

[0008] To address the aforementioned issues, a method for growing gallium oxide crystals with low impurity content is provided. After the gallium oxide crystal growth is completed, the gas inside the furnace is extracted to reduce the impact of noble metal impurities inside the furnace on the quality of the gallium oxide crystal, thereby improving the purity and quality of the gallium oxide crystal and maintaining its internal integrity.

[0009] One aspect of this application provides a gallium oxide crystal with low impurity content, wherein the total impurity density of the gallium oxide crystal is ≤150ppm; wherein the total noble metal impurity density is ≤100ppm; the aluminum impurity density is ≤30ppm; the zirconium impurity density is ≤30ppm; and the iron impurity density is ≤1ppm.

[0010] Optionally, the total precious metal impurities include iridium, platinum, and rhodium, wherein the impurity density of iridium is ≤50ppm; the impurity density of platinum is ≤50ppm; and the impurity density of rhodium is ≤50ppm.

[0011] Optionally, the XRD full width at half maximum (FWHM) of the gallium oxide crystal is ≤50 arcseconds.

[0012] Optionally, the number of cracks larger than 10 μm in the gallium oxide crystal is ≤1 per piece.

[0013] Optionally, the total dislocation density of the gallium oxide crystal is ≤10. 4 / cm 2 .

[0014] Optionally, the area representing 3 / 4 of the diameter of any cross-section of the gallium oxide crystal is the central region, and the area outside the central region is the edge region; the total impurity density of the central region is ≤100ppm; the total noble metal impurity density is ≤80ppm; the aluminum impurity density is ≤5ppm; the zirconium impurity density is ≤5ppm; and the iron impurity density is ≤1ppm. The total impurity density in the edge region is ≤150ppm; the total precious metal impurity density is ≤100ppm; the aluminum impurity density is ≤30ppm; the zirconium impurity density is ≤30ppm; and the iron impurity density is ≤1ppm.

[0015] Optionally, the total precious metal impurities include iridium, platinum, and rhodium, wherein the impurity density of iridium in the central region is ≤40ppm, and the impurity density of iridium in the edge region is ≤50ppm; the impurity density of platinum in the central region is ≤40ppm, and the impurity density of platinum in the edge region is ≤50ppm; the impurity density of rhodium in the central region is ≤40ppm, and the impurity density of rhodium in the edge region is ≤50ppm.

[0016] Optionally, the XRD half-width at half-maximum (WHM) of the central region is ≤30 arcseconds, and the WHM of the edge region is ≤50 arcseconds.

[0017] Optionally, the number of cracks larger than 10 μm in the central region is ≤0 cracks / piece, and the number of cracks larger than 10 μm in the edge region is ≤1 crack / piece.

[0018] Optionally, the total dislocation density of the central region is ≤10. 3 / cm 2 The total dislocation density in the edge region is ≤10 4 / cm 2 .

[0019] Another aspect of this application provides a method for growing gallium oxide crystals with low impurity content, comprising the following steps: S1: Place the precious metal crucible containing gallium oxide powder into the furnace body, wherein the outer surface of the precious metal crucible is provided with a high-temperature resistant adsorption material. S2: Under the condition of introducing protective gas, gallium oxide crystal is grown. After the growth is completed, during the process of cooling the furnace, the gas inside the furnace is extracted. After the temperature inside the furnace is cooled to room temperature, the gallium oxide crystal is taken out.

[0020] First, by incorporating high-temperature resistant adsorption materials, not only can the gaseous noble metals generated in the noble metal crucible at high temperatures be effectively adsorbed, but the heat preservation performance of the noble metal crucible can also be improved, reducing heat loss. Simultaneously, the high-temperature resistant adsorption and insulation materials can optimize the thermal environment during gallium oxide crystal growth, ensuring temperature stability during the growth process, thereby reducing defects caused by temperature fluctuations and improving the quality and uniformity of the gallium oxide crystal. Second, after the gallium oxide crystal growth is completed, extracting the gas containing gaseous noble metals or noble metal oxides from the furnace can further reduce the impurity content in the gallium oxide crystal, improving its purity and quality.

[0021] Specifically, the gallium oxide crystal growth method in this application is not limited. It can be the mode-guided method or the Bridgman method. Any method that can use a crucible to grow gallium oxide crystals is applicable.

[0022] Specifically, when the gallium oxide crystal growth method is the mold-guided method, the outer surface of the mold can be wrapped with a high-temperature resistant adsorption and insulation material to absorb the precious metal material escaping from the mold, thereby improving the absorption effect of the precious metal and thus increasing the recovery rate of the precious metal.

[0023] Optionally, the protective gas in step S1 includes at least one of high-purity air, nitrogen, oxygen, carbon dioxide, and argon.

[0024] Optionally, the high-temperature resistant adsorption material includes either zirconium oxide fiber felt or alumina fiber felt.

[0025] The above-mentioned materials have good high-temperature resistance and can be used for a long time in high-temperature environments. They can also maintain a stable fiber interwoven structure at high temperatures. Through the fiber interwoven structure in the fiber felt, some of the gaseous noble metals and noble metal oxides formed at high temperatures can be adsorbed. At the same time, they have excellent heat insulation and heat preservation effects, which can effectively inhibit heat transfer and reduce heat loss.

[0026] Optionally, the density of the high-temperature resistant adsorbent material is ≤0.5 g / cm³. 3 .

[0027] The density of high-temperature resistant adsorbent materials affects their absorption rate of gases containing precious metals and their oxides. It also affects the stress of gallium oxide crystals in the crucible. If the density of the high-temperature resistant adsorbent material is too high, it will reduce the absorption rate of gases containing precious metals and their oxides. At the same time, the increased density of the high-temperature resistant adsorbent material will increase its thermal conductivity. A higher thermal conductivity will increase the heat dissipation capacity of the crucible, which will in turn increase the stress in the gallium oxide crystal and affect the quality of the gallium oxide crystal product.

[0028] Optionally, the precious metal crucible may be made of one of iridium or a platinum-rhodium alloy.

[0029] Optionally, the process also includes a precious metal recovery step: the gas extracted from the furnace is transported to a recovery box containing an absorption medium, the high-temperature resistant adsorption material and the absorption medium in the recovery box are collected, and then separated and purified to recover the precious metal.

[0030] By using high-temperature resistant adsorption materials and a recovery box to absorb precious metals and their oxides from the gas extracted from the furnace, not only can impurities in gallium oxide crystals be reduced, but also precious metals can be recovered, reducing the production cost of gallium oxide crystals. Furthermore, this application uses both high-temperature resistant adsorption materials and a recovery box to collect precious metals and their oxides, resulting in a higher recovery rate and a greater amount of precious metals recovered compared to existing furnace cleaning methods.

[0031] Specifically, the separation and purification methods in the precious metal recycling process can employ methods commonly used in existing technologies, such as one or a combination of chemical precipitation, solvent extraction, or electrolytic refining.

[0032] Specifically, when the recovered precious metal is iridium, it can be dissolved in aqua regia, precipitated with ammonium chloride to obtain ammonium chloroiridate, and then reduced with hydrogen to obtain pure iridium powder; when the recovered precious metal is a platinum-rhodium alloy, it can be dissolved in aqua regia, separated by ammonium chloride precipitation, and then separated by hydrolysis or extraction.

[0033] Preferably, the separation and purification method is a chemical precipitation method, which specifically includes the following steps: incinerating or acid-dissolving the collected high-temperature resistant adsorbent material and absorption medium to obtain a solution containing precious metals; adding a precipitant to the solution containing precious metals to precipitate the precious metals; filtering, washing, drying, and then reducing at high temperature to obtain elemental precious metals.

[0034] This method is simple to operate, low in cost, and suitable for large-scale industrial production. Compared with a single furnace cleaning method, it can more effectively enrich and separate precious metals and improve the purity of the recovered metals.

[0035] Optionally, the absorption medium includes one of an organic solvent, an acidic solution, or an alkaline solution.

[0036] Specifically, when the precious metal to be recovered is iridium, the absorption medium includes one of the following: disodium ethylenediaminetetraacetate solution, sodium cyanide solution, aqua regia, hydrochloric acid and hydrogen peroxide mixture.

[0037] Preferably, the absorption medium is a mixed solution of aqua regia, hydrochloric acid and hydrogen peroxide.

[0038] Specifically, the mass ratio of the mixed solution of aqua regia, hydrochloric acid and hydrogen peroxide is 1:(1-3):(0.5-2).

[0039] Specifically, when the recovered metal is a platinum-rhodium alloy, the absorption medium includes one of aqua regia, a mixed solution of hydrochloric acid and nitric acid, or molten alkali.

[0040] Optionally, the temperature in the recycling bin during the precious metal recycling process is ≤600℃.

[0041] At this temperature, the extracted gas can be effectively cooled, causing the precious metals and precious metal oxides in the gaseous phase to condense and eventually fall into the adsorption medium in the recovery tank. At the same time, this temperature can reduce the corrosion of equipment pipelines caused by excessively high temperatures and extend the service life of production equipment. In addition, it can also prevent safety problems such as burns to operators caused by high-temperature gas.

[0042] In another aspect of this application, a system for in-situ recovery of precious metals during gallium oxide crystal growth is provided, comprising: a furnace body; a precious metal crucible disposed inside the furnace body, wherein a high-temperature resistant adsorption material is disposed on the outer surface of the precious metal crucible; a recovery tank connected to the interior of the furnace body via a connecting pipe, wherein the recovery tank has an inlet and a outlet, and an absorption medium is disposed in the recovery tank; and a gas transport mechanism whose inlet is connected to the recovery tank.

[0043] Optionally, the recovery tank is also equipped with an observation window and a temperature control mechanism.

[0044] Optionally, the gas transport mechanism includes one of a vacuum pump and an air compressor.

[0045] The beneficial effects of this application include, but are not limited to: 1. The in-situ precious metal recovery system for gallium oxide crystal growth according to this application further reduces the cost of gallium oxide crystal growth by recycling precious metals, and has good economic benefits.

[0046] 2. The in-situ precious metal recovery system for gallium oxide crystal growth according to this application, by incorporating a high-temperature resistant adsorption material, can not only effectively adsorb the gaseous precious metal generated in the precious metal crucible at high temperatures, reducing the impurity content in the gallium oxide crystal, but also improve the heat preservation performance of the precious metal crucible, reducing heat loss. Simultaneously, the high-temperature resistant adsorption and insulation material can optimize the thermal environment during gallium oxide crystal growth, ensuring temperature stability during the growth process, thereby reducing defects caused by temperature fluctuations and improving the quality and uniformity of the gallium oxide crystal.

[0047] 3. According to the method for in-situ recovery of noble metals in gallium oxide crystal growth of this application, by extracting the gas containing noble metals and their oxides in the furnace during the gallium oxide crystal growth process, not only can the noble metals and their oxides be collected, but also the impurities of noble metals can be prevented from entering the crucible and becoming impurities in the gallium oxide crystal, thereby improving the quality of the gallium oxide crystal and maintaining the internal integrity of the gallium oxide crystal.

[0048] 4. According to the method for in-situ recovery of noble metals during gallium oxide crystal growth in this application, by using a low-density high-temperature resistant adsorbent material, not only can the absorption rate of gases containing noble metals and their oxides be improved, but the stress of the gallium oxide crystal growing in the crucible can also be reduced, thereby achieving the recovery and utilization of noble metals without affecting the quality of gallium oxide growth. Attached Figure Description

[0049] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a schematic diagram of the structure of the noble metal in-situ recovery system during gallium oxide crystal growth involved in the embodiments of this application.

[0050] List of components and reference numerals: 1. Precious metal crucible; 2. High-temperature resistant adsorption material; 3. Furnace body; 4. Gas transport mechanism; 5. Absorption medium; 6. Recovery box. Detailed Implementation

[0051] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0052] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this application were all purchased commercially.

[0053] Unless otherwise specified, the methods used in the embodiments and comparative examples of this application are conventional methods in the prior art.

[0054] To more clearly illustrate the overall concept of this application, a detailed description is provided below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0055] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Therefore, the scope of protection of this application is not limited to the specific embodiments disclosed below.

[0056] Furthermore, it should be understood in the description of this application that the terms "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0057] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0058] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0059] In this application, unless otherwise expressly specified and limited, the "above" or "below" of the second feature can mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. In the description of this specification, references to terms such as "an embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in one or more embodiments or examples.

[0060] refer to Figure 1 The embodiments of this application relate to an in-situ precious metal recovery device during gallium oxide crystal growth, comprising: a furnace body 3; a precious metal crucible 1, which is disposed inside the furnace body 3, wherein a high-temperature resistant adsorption material 2 is disposed on the outer surface of the precious metal crucible 1; a recovery box 6, which is connected to the interior of the furnace body 3 via a connecting pipe, and is provided with a liquid inlet and a liquid outlet, and is provided with an absorption medium 5, which is used to absorb precious metals and their oxides; and a gas transport mechanism 4, the gas inlet of which is connected to the recovery box 6.

[0061] By coating the outer surface of the precious metal crucible 1 with a high-temperature resistant adsorbent material 2, and if the gallium oxide crystal growth is carried out using the guided mold method, the outer surface of the precious metal mold for the gallium oxide crystal is also coated with a high-temperature resistant adsorbent material 2. Then, the precious metal mold coated with the high-temperature resistant adsorbent material 2 is placed into the precious metal crucible 1 coated with the high-temperature resistant adsorbent material 2, and together they are placed into the furnace body 3. An inert gas is introduced to heat the crucible to a suitable temperature, promoting gallium oxide crystal growth. During the gallium oxide crystal growth process, the precious metal atoms in the precious metal crucible 1 and the precious metal mold become gaseous or transform into volatile oxides. These gaseous substances pass through the high-temperature resistant adsorbent material 2 and enter the furnace body 3. During the process of detaching from the precious metal crucible 1 or precious metal mold, the high-temperature resistant adsorbent material 2 adsorbs some gaseous precious metals or gaseous precious metal oxides. After the gallium oxide crystal growth is completed, when cooling is performed, the gas transport mechanism 4 is activated simultaneously to extract the gas containing gaseous precious metals and precious metal oxides from the furnace body 3 and transport it to the recovery box 6 through the connecting pipeline. The recovery box 6 contains the absorption medium 5. The gaseous precious metals and precious metal oxides in the gas enter the absorption medium 5 through dissolution absorption and condensation deposition. Then, the high-temperature resistant adsorbent material 2 and the absorption medium 5 in the recovery box 6 are collected, and the precious metals are separated and purified from them, realizing the in-situ recovery of precious metals.

[0062] This system effectively adsorbs and collects gaseous precious metals and precious metal oxides generated by the precious metal crucible 1 and the precious metal mold through the synergistic method of high-temperature resistant materials and absorption medium 5. This not only improves the adsorption and collection rate of gaseous precious metals and precious metal oxides, facilitating subsequent separation and purification, but also improves the recovery rate of precious metals and reduces the cost of gallium oxide crystal growth.

[0063] As one implementation method, the recovery tank 6 is also equipped with an observation window and a temperature control mechanism.

[0064] Under this setting, the color of the adsorption medium in the recovery box 6 is observed through the observation window. After confirming that the content of precious metals in the adsorption medium has reached saturation based on the change in color depth, the adsorption medium is collected and then the precious metals are separated and purified.

[0065] Specifically, the temperature control mechanism can be a commonly used temperature control mechanism in the prior art, as long as it can achieve temperature regulation in the recycling box 6. For example, it can include at least one of heating wire, cooling coil and thermocouple.

[0066] In one implementation, the gas transport mechanism 4 includes one of a vacuum pump and an air compressor.

[0067] Example 1 This embodiment relates to a method for growing gallium oxide crystals with low impurity content, employing the aforementioned in-situ noble metal recovery device during gallium oxide crystal growth, and includes the following steps: S1: Place the iridium crucible containing gallium oxide powder into the furnace body, wherein the outer surface of the iridium crucible is coated with a powder having a density of 0.3 g / cm³. 3 Zirconia fiber soft felt; S2: Under nitrogen gas conditions, gallium oxide crystals are grown using the vertical Bridgman method. After 100 hours of growth, during the furnace cooling process, a vacuum pump is started to extract the gas containing iridium and iridium oxide from the furnace. After the temperature in the furnace cools down to room temperature, the gallium oxide crystals are taken out. Precious metal recovery steps: The gas containing iridium and iridium oxide extracted from the furnace is transported to a recovery tank containing aqua regia. The aqua regia is a mixed solution of hydrochloric acid, nitric acid, and hydrogen peroxide in a mass ratio of 1:2:1, with hydrochloric acid concentration of 36%, nitric acid concentration of 65%, and hydrogen peroxide concentration of 30%. The zirconia fiber felt and the aqua regia solution in the recovery tank are collected and separated and purified. The specific separation and purification method is as follows: After incinerating the collected zirconia fiber felt, the residue is dissolved with aqua regia (addition amount is specified) twice the weight of the residue to obtain an iridium-containing solution. The aqua regia containing iridium and its oxide in the recovery tank is combined with the above iridium-containing solution, and ammonium chloride (addition amount is specified) 1.2 times the weight of the residue is added to precipitate, resulting in ammonium chloroiridate precipitate. After filtration, washing, and drying, it is reduced at 800℃ in a hydrogen atmosphere to obtain elemental iridium, and the precious metal is recovered.

[0068] Among them, the weight of the iridium crucible was reduced by 4.75g during the gallium oxide crystal growth process, and 3.56g of iridium was recovered from the aqua regia in the zirconium oxide fiber felt and the recovery box, with an iridium recovery rate of 74.95%.

[0069] Example 2 This embodiment relates to a method for growing gallium oxide crystals with low impurity content, employing the aforementioned in-situ noble metal recovery device during gallium oxide crystal growth, and includes the following steps: S1: Place the iridium crucible containing gallium oxide powder into the furnace body. A mold is placed inside the iridium crucible. Both the outer surfaces of the iridium crucible and the outer surfaces of the mold are coated with a powder having a density of 0.25 g / cm³. 3 Zirconia fiber soft felt; S2: Under nitrogen gas conditions, gallium oxide crystals are grown using the guided model method. After 100 hours of growth, during the furnace cooling process, a vacuum pump is started to extract the gas containing iridium and iridium oxide from the furnace. After the temperature in the furnace cools down to room temperature, the gallium oxide crystals are taken out. Precious metal recovery steps: The gas containing iridium and iridium oxide extracted from the furnace is transported to a recovery tank containing aqua regia. The aqua regia is a mixed solution of hydrochloric acid, nitric acid, and hydrogen peroxide in a mass ratio of 1:2:1, with the concentrations of hydrochloric acid (38%), nitric acid (68%), and hydrogen peroxide (30%). The temperature in the recovery tank is 400°C. Zirconia fiber felt and the aqua regia solution in the recovery tank are collected and separated and purified. The specific separation and purification method is the same as in Example 1, and the precious metals are recovered.

[0070] Among them, the weight of the iridium crucible was reduced by 4.23g and the weight of the iridium mold was reduced by 1.86g during the gallium oxide crystal growth process. 5.07g of iridium was recovered from the aqua regia in the zirconium fiber felt and recycling box, with an iridium recovery rate of 83.3%.

[0071] Example 3 This embodiment relates to a method for growing gallium oxide crystals with low impurity content, employing the aforementioned in-situ noble metal recovery device during gallium oxide crystal growth, and includes the following steps: S1: Place the platinum-rhodium alloy crucible containing gallium oxide powder into the furnace body, wherein the outer surface of the platinum-rhodium alloy crucible is coated with a powder having a density of 0.35 g / cm³. 3 alumina fiber soft felt; S2: Under nitrogen gas conditions, gallium oxide crystals are grown using the vertical Bridgman method. After 100 hours of growth, during the furnace cooling process, a vacuum pump is started to extract the gas containing platinum-rhodium alloy and platinum-rhodium alloy oxide from the furnace. After the temperature in the furnace cools down to room temperature, the gallium oxide crystals are taken out. Precious metal recovery steps: The gas containing platinum-rhodium alloy and platinum-rhodium alloy oxide extracted from the furnace is transported to a recovery tank containing aqua regia. The aqua regia is a mixed solution of hydrochloric acid, nitric acid, and hydrogen peroxide in a mass ratio of 1:2:1, with hydrochloric acid concentration of 38%, nitric acid concentration of 68%, and hydrogen peroxide concentration of 30%. The temperature in the recovery tank is 450℃. The alumina fiber felt and the aqua regia solution in the recovery tank are collected and separated and purified. The specific separation and purification method is as follows: After incinerating the collected alumina fiber felt, the residue is dissolved in aqua regia at twice the weight of the residue to obtain a platinum-rhodium solution. The aqua regia absorbent in the recovery tank is combined with the above platinum-rhodium solution, and ammonium chloride precipitate at 1.2 times the weight of the residue is added to separate ammonium chloroplatinate precipitate. The remaining solution is separated from rhodium by hydrolysis or extraction. Platinum powder and rhodium powder are obtained by hydrogen reduction, and platinum and rhodium precious metals are recovered.

[0072] During the gallium oxide crystal growth process, the weight of the platinum-rhodium alloy crucible was reduced by 5.24g, and 3.35g of platinum and 1.44g of rhodium were recovered from the aqua regia in the alumina fiber felt and recycling box, for a total recovery of 4.79g of platinum and rhodium, with a platinum-rhodium alloy recovery rate of 91.5%.

[0073] Test Example 1 The gallium oxide crystals obtained in Examples 1-3 were tested, and the test results are shown in Table 1-2. The specific testing method is as follows: The impurity density was tested by inductively coupled plasma mass spectrometry (ICP-MS) to detect the content of iridium or platinum-rhodium impurities in gallium oxide crystals. The method for measuring the full width at half maximum (FWHM) is to analyze the FWHM of the crystal rocking curve using an X-ray diffractometer (XRD). The method for testing the number of cracks is to observe the crystal surface and cross-section using an optical microscope and count the number of cracks with a length greater than 10 μm.

[0074] The method for testing dislocation density is to use chemical etching combined with optical microscopy to count the number of corrosion pits. The stacking fault density is tested by using transmission electron microscopy (TEM) to count the number of stacking faults.

[0075] Table 1

[0076] As can be seen from the data in Table 1, the precious metal recovery rates of Examples 1-3 are all high, indicating that the high-temperature resistant adsorbent material and the recovery box provided in this application can effectively capture volatile precious metals. Examples 2 and 3 show even higher recovery rates, indicating that coating the surface of the precious metal mold with the high-temperature resistant adsorbent material further reduces the escape of precious metals. Example 3 shows a recovery rate of up to 91.5% for the platinum-rhodium alloy, demonstrating that this method has good applicability to different precious metal materials.

[0077] From the perspective of gallium oxide crystal quality, the low-density high-temperature resistant adsorbent material (0.25 g / cm³ in Example 2) has better crystal quality than the higher-density material (0.3 g / cm³ in Example 1), indicating that the low-density adsorbent material has a better heat preservation effect on the crucible, which is beneficial to reducing the thermal stress of the crystal.

[0078] Table 2

[0079] The above description is merely an embodiment of this application, and the scope of protection of this application is not limited to these specific embodiments, but is determined by the claims of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the technical concept and principles of this application should be included within the scope of protection of this application.

Claims

1. A gallium oxide crystal with low impurity content, characterized in that, The total impurity density in the gallium oxide crystal is ≤150ppm; wherein, the total noble metal impurity density is ≤100ppm; the aluminum impurity density is ≤30ppm; the zirconium impurity density is ≤30ppm; and the iron impurity density is ≤1ppm.

2. The gallium oxide crystal with low impurity content according to claim 1, characterized in that, The total precious metal impurities include iridium, platinum, and rhodium, wherein the impurity density of iridium is ≤50ppm; the impurity density of platinum is ≤50ppm; and the impurity density of rhodium is ≤50ppm.

3. The gallium oxide crystal with low impurity content according to claim 1, characterized in that, The XRD full width at half maximum (FWHM) of the gallium oxide crystal is ≤50 arcseconds; and / or The number of cracks larger than 10 μm in the gallium oxide crystal is ≤1 per piece.

4. The gallium oxide crystal with low impurity content according to claim 1, characterized in that, The total dislocation density of the gallium oxide crystal is ≤10. 4 / cm 2 .

5. The gallium oxide crystal with low impurity content according to claim 1, characterized in that, The central region is defined as the area 3 / 4 of the diameter of any cross-section of the gallium oxide crystal, and the area outside the central region is defined as the edge region; the total impurity density of the central region is ≤100ppm; the total noble metal impurity density is ≤80ppm; the aluminum impurity density is ≤5ppm; the zirconium impurity density is ≤5ppm; and the iron impurity density is ≤1ppm. The total impurity density in the edge region is ≤150ppm; the total precious metal impurity density is ≤100ppm; the aluminum impurity density is ≤30ppm; the zirconium impurity density is ≤30ppm; and the iron impurity density is ≤1ppm.

6. The gallium oxide crystal with low impurity content according to claim 5, characterized in that, The total precious metal impurities include iridium, platinum, and rhodium, wherein the impurity density of iridium in the central region is ≤40ppm and the impurity density of iridium in the edge region is ≤50ppm; the impurity density of platinum in the central region is ≤40ppm and the impurity density of platinum in the edge region is ≤50ppm; the impurity density of rhodium in the central region is ≤40ppm and the impurity density of rhodium in the edge region is ≤50ppm.

7. The gallium oxide crystal with low impurity content according to claim 5, characterized in that, The XRD half-width at half-maximum (WHM) of the central region is ≤30 arcseconds; the WHM of the edge region is ≤50 arcseconds; and / or The number of cracks larger than 10μm in the central region is ≤0 per piece; the number of cracks larger than 10μm in the edge region is ≤1 per piece.

8. The gallium oxide crystal with low impurity content according to claim 5, characterized in that, The total dislocation density in the central region is ≤10. 3 / cm 2 The total dislocation density in the edge region is ≤10. 4 / cm 2 .

9. A method for growing gallium oxide crystals with low impurity content, characterized in that, Includes the following steps: S1: Place the precious metal crucible containing gallium oxide powder into the furnace body, wherein the outer surface of the precious metal crucible is provided with a high-temperature resistant adsorption material. S2: Under the condition of introducing protective gas, gallium oxide crystal is grown. After the growth is completed, during the process of cooling the furnace, the gas inside the furnace is extracted. After the temperature inside the furnace is cooled to room temperature, the gallium oxide crystal is taken out.

10. The method for growing gallium oxide crystals with low impurity content according to claim 1, characterized in that, It also includes a precious metal recovery step: the gas extracted from the furnace is transported to a recovery box containing an absorption medium, the high-temperature resistant adsorption material and the absorption medium in the recovery box are collected, and then separated and purified to recover the precious metals.

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