Gallium oxide and synthetic method thereof

Abstract

The invention belongs to the field of semiconductor materials, and discloses gallium oxide and a synthesis method thereof. The synthesis method comprises the following steps: introducing ammonia water into a gallium nitrate solution, and continuously stirring to obtain a white turbid liquid; aging the white turbid liquid, filtering and washing to obtain an intermediate product; and calcining the intermediate product to obtain solid particles which are gallium oxide. According to the synthesis method, gallium nitrate and ammonia water are used as core raw materials, additional additives and complex precursors are not needed, the impurity introduction risk can be greatly reduced, and the high purity of the product can be guaranteed by combining washing and calcining procedures; meanwhile, the process steps are simple, the operation conditions are mild and controllable, expensive special equipment is not needed, the production cost is low, the method is suitable for large-scale production, and a gallium oxide product with good dispersity and high crystallinity can be obtained after a precursor prepared through a precipitation method is calcined and crushed.

Description

Gallium oxide and its synthesis method Technical Field

[0001] This invention belongs to the field of semiconductor materials and relates to a gallium oxide production process, specifically to gallium oxide and its synthesis method. Background Technology

[0002] Gallium oxide (GaO), as a new generation of ultra-wide bandgap semiconductor material, boasts a bandgap of approximately 4.9 eV and extremely high breakdown electric field strength, demonstrating superior theoretical performance compared to silicon, silicon carbide, and gallium nitride in the fabrication of high-voltage, low-conduction-loss power devices. Currently, the demand for GaO in applications such as fast charging for new energy vehicles, smart grids, and deep ultraviolet detection continues to rise.

[0003] Current gallium oxide (GaO) synthesis technologies have formed a diversified system, mainly divided into two categories: gas-phase methods and liquid-phase methods. In the gas-phase method, chemical vapor deposition (CVD) can prepare high-quality GaO materials by controlling precursor concentration and reaction temperature, while molecular beam epitaxy (MBE) can achieve atomic-level thin film growth. However, both methods suffer from high equipment costs and complex process flows. Liquid-phase methods, represented by sol-gel and chemical bath deposition, generate GaO through solution-phase reactions, offering advantages such as simple operation and lower cost. The sol-gel method can achieve nanoscale uniform dispersion of GaO, but it requires multiple steps including precursor preparation, gelation, and heat treatment. In addition, electrophoretic deposition and laser evaporation technologies are also used in specific applications. These methods prepare GaO materials through electric fields or high-energy lasers, respectively, but their implementation relies on precise control of specific process parameters. Although existing GaO synthesis technologies can achieve basic material preparation, there is still significant room for optimization in terms of precise particle size control and process simplification.

[0004] Existing gallium oxide synthesis technologies generally suffer from problems such as complex processes, cumbersome raw material systems, high risk of impurity introduction, and high production costs and equipment requirements, making it difficult to simultaneously meet the actual needs of product purity, process stability, and large-scale applications. On the one hand, mainstream liquid-phase processes such as sol-gel, chemical bath deposition, hydrothermal / solvothermal, and coprecipitation typically require multiple gallium sources, such as gallium acetate, gallium chloride, and alkoxides, along with auxiliary reagents such as sodium hydroxide, urea, complexing agents, dispersants, or organic templates. Some processes also require the introduction of doping ions or surfactants. This not only increases the number of steps and the difficulty of process control, but also makes it easy for additive residues, by-reaction products, or salt impurities to be difficult to thoroughly clean, leading to a decrease in gallium oxide purity and thus affecting key performance characteristics such as device breakdown voltage and stability. On the other hand, vapor / physical deposition processes such as chemical vapor deposition (CVD), metal-organic vapor phase epitaxy (MOVPE), molecular beam epitaxy (MBE), and pulsed laser deposition (PLD) rely on high-precision reaction equipment, complex atmosphere ratios, and stringent temperature control, resulting in high equipment investment and operating costs. Furthermore, they are prone to introducing impurities due to insufficient gas source purity and chamber contamination. The overall process flow is lengthy and the operating conditions are harsh, which is not conducive to the large-scale, low-cost, and stable preparation of high-purity gallium oxide materials. Summary of the Invention

[0005] In view of the defects and deficiencies of the existing technology, the present invention provides a method for synthesizing gallium oxide in two aspects: firstly, the present invention provides gallium oxide in two aspects.

[0006] In a first aspect, the present invention provides a method for synthesizing gallium oxide, comprising the following steps: Step 1, ammonia water is introduced into a gallium nitrate solution and stirred continuously to obtain a white suspension; Step 2, the white suspension is aged, filtered, and washed with water to obtain an intermediate product; Step 3, the intermediate product is calcined to obtain solid particles, which are the gallium oxide.

[0007] Preferably, in step 1, the concentration of the gallium nitrate solution is 0.25~0.5 mol / L; and the concentration of the ammonia solution is 10~25 wt%.

[0008] Preferably, in step 1, ammonia water is introduced until the pH value of the reaction system is 7.5~8.5.

[0009] Preferably, in step 1, the flow rate of ammonia water is 5~15 mL / min.

[0010] Preferably, in step 1, the reaction temperature is 5~95℃ and the reaction time is 1.5~2.5h.

[0011] Preferably, in step 1, the stirring rate is 250~350 rpm; the stirring time is 1.5~2.5 h.

[0012] Preferably, in step 2, the aging temperature is 5~95℃ and the aging time is 2~3h.

[0013] Preferably, in step 2, the washing is performed multiple times until the conductivity of the washing effluent is less than 50 μS / cm.

[0014] Preferably, in step 3, the calcination temperature is 700~900℃; the calcination time is 3~5h.

[0015] Preferably, in step 3, the solid particles obtained by calcination are crushed and sieved to obtain gallium oxide.

[0016] Secondly, the present invention provides gallium oxide, which is prepared by the above-described synthesis method, wherein the particle size of the gallium oxide is 0.5~15μm and the particle morphology of the gallium oxide is rod-shaped.

[0017] Compared with the prior art, one or more technical solutions provided by the present invention have one of the following beneficial effects: (1) The synthesis method of the present invention uses gallium nitrate and ammonia as core raw materials, without the need to add other additives or prepare complex precursors. The system is simple and the risk of impurity introduction is low. Combined with the water washing and calcination process, the high purity of the product can be effectively guaranteed. At the same time, the process steps are simplified, the operating conditions are mild and controllable, no special expensive equipment is required, the production cost is low, and it is suitable for large-scale production. The precursor synthesized by precipitation method can be calcined and crushed to obtain gallium oxide products with good dispersibility and excellent crystallinity.

[0018] (2) The synthesis method of the present invention can precisely control the size and agglomeration characteristics of the precursor particles by adjusting the concentration of gallium nitrate solution, the rate of ammonia water introduction and the aging temperature. Combined with a gentle crushing process, the product particle size can be adjusted in a wide range of 0.5~10μm. At the same time, the water washing process can effectively remove impurity ions and ensure product purity. The overall process has strong adaptability and low cost, and is suitable for large-scale preparation of gallium oxide materials with different particle sizes to meet the needs of multiple application scenarios. Attached Figure Description

[0019] Figure 1 is a SEM image of gallium oxide obtained in Example 1; Figure 2 is a SEM image of gallium oxide obtained in Example 2. Detailed Implementation

[0020] The present invention provides the following specific technical solutions.

[0021] In a first aspect, the present invention provides a method for synthesizing gallium oxide, comprising the following steps: Step 1, ammonia water is introduced into a gallium nitrate solution and stirred continuously to obtain a white suspension; Step 2, the white suspension is aged, filtered, and washed with water to obtain an intermediate product; Step 3, the intermediate product is calcined to obtain solid particles, which are the gallium oxide.

[0022] Through research, the inventors discovered that the process of this invention uses gallium nitrate and ammonia as core raw materials, without the need to add other additives or prepare complex precursors. The system is simple and has a low risk of introducing impurities. The combination of water washing and calcination processes can effectively ensure the high purity of the product. At the same time, the process steps are simplified, the operating conditions are mild and controllable, no special expensive equipment is required, the production cost is low, and it is suitable for large-scale production. The precursor synthesized by precipitation method can be calcined and crushed to obtain gallium oxide products with good dispersibility and excellent crystallinity.

[0023] Preferably, in step 1, the concentration of the gallium nitrate solution is 0.25~0.5 mol / L; and the concentration of the ammonia solution is 10~25 wt%.

[0024] Preferably, in step 1, ammonia water is introduced until the pH value of the reaction system is 7.5~8.5.

[0025] Preferably, in step 1, the flow rate of ammonia water is 5~15 mL / min.

[0026] The inventors discovered that if the ammonia flow rate is below 5 mL / min, although the ammonia can diffuse uniformly in the reaction system, the slow addition rate will cause the local pH of the system to remain low, resulting in a nucleation rate of gallium oxide precursor that is far lower than the growth rate. This ultimately leads to excessive particle growth, with particle sizes exceeding the preferred range of 15 μm. Simultaneously, it significantly prolongs the reaction time, reduces production efficiency, and increases the cost of large-scale production. If the ammonia flow rate is above 15 mL / min, it will cause a sudden local excess of ammonia, causing a rapid rise in the system pH. This results in a large number of precursor nucleations and the formation of numerous ultrafine particles. These particles exhibit severe agglomeration due to van der Waals forces and cannot form regular rod-like morphologies. Furthermore, the locally alkaline reaction environment can lead to incomplete hydrolysis of ammonia, introducing ammonium salt impurities and thus reducing product purity.

[0027] Preferably, in step 1, the reaction temperature is 5~95℃.

[0028] The inventors discovered that if the reaction temperature in step 1 is below 5°C, the ion diffusion rate and reaction kinetics within the system will be significantly slowed down, resulting in a precursor nucleation rate that is much greater than the growth rate. This leads to excessively fine particles that are prone to agglomeration, preventing the normal development of a rod-like morphology. Simultaneously, low temperatures increase the viscosity of the suspension, reducing the efficiency of subsequent centrifugal washing. If the reaction temperature is above 95°C, the volatility of ammonia causes rapid evaporation, leading to decreased pH control precision and localized pH fluctuations. This results in irregular particle growth and the formation of large, coarse particles. Furthermore, high temperatures disrupt the crystal development of the precursor, reducing the crystallinity of the final product and completely eliminating the rod-like morphology. By controlling the reaction temperature within the preferred range of 5–95°C, the temperature's influence on the ion diffusion rate and reaction kinetics can be used to achieve a reasonable match between the particle nucleation rate and growth rate. Higher temperatures result in faster ion diffusion and reaction kinetics, relatively lowering the nucleation rate and relatively increasing the growth rate, making it easier to form larger particles. This allows for effective and precise control of the resulting gallium oxide material particle size.

[0029] Preferably, in step 1, the stirring rate is 250~350 rpm; the stirring time is 1.5~2.5 h.

[0030] Preferably, in step 2, the aging temperature is 5~95℃ and the aging time is 2~3h.

[0031] Preferably, in step 2, the washing is performed multiple times until the conductivity of the washing effluent is less than 50 μS / cm.

[0032] In practical applications, centrifugal separation technology can be used to simultaneously complete solid-liquid separation and water washing.

[0033] Preferably, in step 3, the calcination temperature is 700~900℃; the calcination time is 3~5h.

[0034] The inventors discovered that if the calcination temperature is below 800℃, the gallium oxide precursor cannot be completely decomposed and transformed into β-phase gallium oxide. A large amount of GaOOH intermediate phase will exist in the system, resulting in phase impurity. The product exhibits a flocculent, loose structure without a distinct rod-like morphology, significantly reduced crystallinity, and a marked decrease in core semiconductor properties such as breakdown electric field strength, failing to meet the application requirements of high-voltage power devices. If the calcination temperature exceeds 800℃, the high temperature causes the gallium oxide particles to melt and sinter, forming strongly bonded hard agglomerates, or even molten blocks, with particle sizes far exceeding the preferred range of 15μm. The rod-like morphology is also completely destroyed, resulting in a significant reduction in the specific surface area of ​​the product and extremely poor dispersibility. Furthermore, the formed hard blocks are difficult to disperse using conventional crushing processes, resulting in extremely low sieve yields and rendering them unsuitable for industrial applications.

[0035] Preferably, in step 3, after crushing and sieving, the resulting solid particles are gallium oxide.

[0036] Secondly, the present invention provides gallium oxide, which is prepared by the above-described synthesis method, wherein the particle size of the gallium oxide is 0.5~15μm; and the particle morphology of the gallium oxide is rod-shaped or prismatic.

[0037] To make the technical problems, technical solutions and technical advantages of the present invention clearer, a detailed description will be given below with reference to specific examples. However, the scope of protection of the present invention is not limited to the following specific embodiments.

[0038] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0039] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0040] Example 1: A method for synthesizing gallium oxide, comprising the following steps: Step 1, using a 0.5 mol / L gallium nitrate solution as the reaction substrate, placing the substrate in a reactor, controlling the reaction temperature at 5°C, continuously stirring at a rate of 300 rpm, and then slowly adding 25% ammonia solution at a flow rate of 15 mL / min until the pH of the system stabilizes at 7.5-8.5, reacting for 2 hours to obtain a white suspension; Step 2, allowing the obtained white suspension to stand and age at 5°C for 2 hours to obtain a slurry; Step 3... Step 3: Centrifuge the slurry and discard the supernatant; resuspend the precipitate in deionized water and repeatedly centrifuge and wash until the conductivity of the washing effluent is less than 50 μS / cm to obtain the precursor; Step 4: Place the washed precursor in a muffle furnace and calcine it at a heating rate of 2℃ / min to 800℃ in air atmosphere for 4 hours to obtain β-phase gallium oxide; Step 5: Crush the calcined β-phase gallium oxide with a hammer mill and then pass it through a 400-mesh standard sieve to obtain β-Ga2O3 powder product.

[0041] Figure 1 is a SEM image of gallium oxide prepared in Example 1. As can be seen from Figure 1, the prepared gallium oxide powder mainly exhibits a regular rod-shaped morphology with a large aspect ratio, good overall dispersion, and no obvious agglomeration. The particle size distribution is relatively uniform, and the diameter and length of the rod-shaped structure are within a controllable range, with high crystallinity.

[0042] Example 2: A method for synthesizing gallium oxide, comprising the following steps: Step 1, using a 0.25 mol / L gallium nitrate solution as the reaction base liquid; placing the base liquid in a reactor, controlling the temperature at 50°C, continuously stirring at 250 rpm, and then slowly adding 10 wt% ammonia water at a rate of 5 mL / min until the pH of the system stabilizes at 7.5-8.5, and reacting for 1.5 h to obtain a white suspension.

[0043] Step 2: Let the obtained suspension stand at 50°C for 2 hours to obtain the slurry.

[0044] Step 3: Centrifuge the slurry and discard the supernatant; resuspend the precipitate with deionized water and repeatedly centrifuge and wash until the conductivity of the washing effluent is less than 50 μS / cm to obtain the precursor.

[0045] Step 4: Place the washed precursor in a muffle furnace and calcine it at 700°C for 5 hours in air atmosphere at a heating rate of 5°C / min to obtain β-phase gallium oxide.

[0046] Step 5: The calcined β-phase gallium oxide is crushed using a hammer mill and then passed through a 400-mesh standard sieve to obtain β-Ga2O3 powder product.

[0047] Figure 2 is a SEM image of gallium oxide prepared in Example 2. As can be seen from Figure 2, the prepared gallium oxide powder exhibits a uniform short rod-shaped (quasi-columnar) morphology. The overall morphology of the particles is regular, with a moderate aspect ratio and good consistency. The powder particles have excellent dispersibility, no obvious agglomeration, uniform size distribution, and the diameter and length of the individual particles are within a controllable range. The crystal outline is clear, showing a high degree of crystallinity.

[0048] Example 3: A method for synthesizing gallium oxide, comprising the following steps: Step 1, using a 0.3 mol / L gallium nitrate solution as the reaction base liquid; placing the base liquid in a reactor, controlling the temperature at 95°C, continuously stirring at 350 rpm, and then slowly adding 20 wt% ammonia water at a rate of 10 mL / min until the pH of the system stabilizes at 7.5-8.5, and reacting for 2.5 h to obtain a white suspension.

[0049] Step 2: Let the obtained suspension stand at 95°C for 3 hours to obtain the slurry.

[0050] Step 3: Centrifuge the slurry and discard the supernatant; resuspend the precipitate with deionized water and repeatedly centrifuge and wash until the conductivity of the washing effluent is less than 50 μS / cm to obtain the precursor.

[0051] Step 4: Place the washed precursor in a muffle furnace and calcine it at 900°C for 3 hours in air atmosphere at a heating rate of 2°C / min to obtain β-phase gallium oxide.

[0052] Step 5: The calcined β-phase gallium oxide is crushed using a hammer mill and then passed through a 400-mesh standard sieve to obtain β-Ga2O3 powder product.

[0053] Comparative Example 1: A method for synthesizing gallium oxide, which differs from Example 1 in that, in step 1, a 0.5 mol / L gallium nitrate solution is used as the reaction base liquid; the base liquid is placed in a reactor, the temperature is controlled at 0°C, and the mixture is continuously stirred at 300 rpm. Then, 25% ammonia water is slowly added dropwise at a rate of 15 mL / min until the pH of the system stabilizes at 7.5-8.5. The reaction is carried out for 2 hours to obtain a white suspension.

[0054] Step 2: Let the obtained suspension stand at 0°C for 2 hours to obtain the slurry.

[0055] Steps 3-5 are the same as in Example 1.

[0056] Comparative Example 2: A method for synthesizing gallium oxide, which differs from Example 1 in that, in step 1, a 0.5 mol / L gallium nitrate solution is used as the reaction substrate; the substrate is placed in a reactor, the temperature is controlled at 110°C, and the mixture is continuously stirred at 300 rpm. Then, 25% ammonia water is slowly added dropwise at a rate of 15 mL / min until the pH of the system stabilizes at 7.5-8.5. The reaction is carried out for 2 hours to obtain a white suspension.

[0057] Step 2: Let the obtained suspension stand at 110°C for 2 hours to obtain the slurry.

[0058] Steps 3-5 are the same as in Example 1.

[0059] Comparative Example 3: A method for synthesizing gallium oxide, comprising the following steps: Steps 1 to 3 are the same as in Example 1.

[0060] Step 4: Place the washed precursor in a muffle furnace and calcine it at 600°C for 4 hours in air atmosphere at a heating rate of 2°C / min to obtain β-phase gallium oxide.

[0061] Step 5: The calcined β-phase gallium oxide is crushed using a hammer mill and then passed through a 400-mesh standard sieve to obtain β-Ga2O3 powder product.

[0062] Comparative Example 4: A method for synthesizing gallium oxide, comprising the following steps: Steps 1 to 3 are the same as in Example 1.

[0063] Step 4: Place the washed precursor in a muffle furnace and calcine it at 1000℃ for 4 hours in air atmosphere at a heating rate of 2℃ / min to obtain β-phase gallium oxide.

[0064] Step 5: The calcined β-phase gallium oxide is crushed using a hammer mill and then passed through a 400-mesh standard sieve to obtain β-Ga2O3 powder product.

[0065] Comparative Example 5: A method for synthesizing gallium oxide, comprising the following steps: Step 1, using a 0.5 mol / L gallium nitrate solution as the reaction base liquid; placing the base liquid in a reactor, controlling the temperature at 5°C, continuously stirring at 300 rpm, and then slowly adding 25% ammonia water at a rate of 2 mL / min until the pH of the system stabilizes at 7.5-8.5, and reacting for 2 h to obtain a white suspension.

[0066] Steps 2-5 are the same as in Example 1.

[0067] Comparative Example 6: A method for synthesizing gallium oxide, comprising the following steps: Step 1, using a 0.5 mol / L gallium nitrate solution as the reaction base liquid; placing the base liquid in a reactor, controlling the temperature at 5°C, continuously stirring at 300 rpm, and then slowly adding 25% ammonia water at a rate of 20 mL / min until the pH of the system stabilizes at 7.5-8.5, and reacting for 2 hours to obtain a white suspension.

[0068] Steps 2-5 are the same as in Example 1.

[0069] The impurity content and particle size of gallium oxide prepared in Examples 1-3 and Comparative Examples 1-6 were tested. The test data are shown in Table 1 below.

[0070] As shown in Table 1, the gallium oxide prepared in Examples 1-3 using the preferred process parameters of this invention all met the 5N high purity standard, with the content of each impurity element being <1ppm and NO3 <1ppm. -The content is <10ppm, the particle size is controlled within a reasonable range of 4~5μm, 1~3μm, and 8~10μm respectively, the morphology is distinctive and all maintain good dispersibility, there is no agglomeration, and the crystallinity is at a medium to high level. Comparative Examples 1-6 deviated from the optimal process ranges for reaction / aging temperature, calcination temperature, and ammonia flow rate, respectively, resulting in significant deterioration in product performance. Except for Comparative Examples 4 and 5, which did not exceed the impurity limit and maintained a purity of 5N, the purity of the other comparative examples dropped to the 4N level, and they generally had problems such as increased impurity element content, excessive anions, or residual characteristic groups. The particle size deviated from the optimal range of 0.5-15μm, or was either too fine (0.02-0.4μm) or too coarse (16-30μm). In terms of morphology, they exhibited defects such as irregular rod-shaped morphology, amorphous particles, flocculent loose structure, and molten blocky structures, accompanied by varying degrees of agglomeration and decreased crystallinity. Comparative Example 4 also showed process defects such as hard lumps that were difficult to break and extremely low sieve yield. The above results fully demonstrate the key role of the preferred process conditions in the preparation of high-performance gallium oxide. Under the preferred process conditions proposed in this invention, gallium oxide products with high purity, uniform morphology, and good dispersion can be prepared. Moreover, the preparation process of this invention is simple and easy to implement, which is conducive to industrial promotion and application.

[0071] The above-described embodiments are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope of the present invention, based on the technical solution and concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for synthesizing gallium oxide, characterized in that, The process includes the following steps: Step 1, ammonia water is introduced into a gallium nitrate solution and stirred continuously to obtain a white suspension; Step 2, the white suspension is aged, filtered, and washed with water to obtain an intermediate product; Step 3, the intermediate product is calcined to obtain gallium oxide as the solid particles.

2. The method for synthesizing gallium oxide as described in claim 1, characterized in that, In step 1, the reaction temperature is 5~95℃; the reaction time is 1.5~2.5h.

3. The method for synthesizing gallium oxide as described in claim 1, characterized in that, In step 3, the calcination temperature is 700~900℃; the calcination time is 3~5h.

4. The method for synthesizing gallium oxide as described in claim 1, characterized in that, In step 2, the aging temperature is 5~95℃; the aging time is 2~3h.

5. The method for synthesizing gallium oxide as described in claim 1, characterized in that, In step 1, the concentration of gallium nitrate solution is 0.25~0.5mol / L; the concentration of ammonia is 10~25wt%; and the flow rate of ammonia is 5~15mL / min.

6. The method for synthesizing gallium oxide as described in claim 1, characterized in that, In step 1, ammonia water is introduced until the pH of the reaction system is 7.5~8.

5.

7. The method for synthesizing gallium oxide as described in claim 1, characterized in that, In step 1, the stirring speed is 250~350 rpm.

8. The method for synthesizing gallium oxide as described in claim 1, characterized in that, In step 2, the washing is repeated multiple times until the conductivity of the washing effluent is less than 50 μS / cm.

9. A gallium oxide, characterized in that, The gallium oxide particles are prepared by the synthesis method according to any one of claims 1 to 8, wherein the particle size is 0.5 to 15 μm and the particle morphology is rod-shaped or prismatic.

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