CN116874285B

CN116874285B - Crucible for growing gallium oxide crystals and preparation method thereof

Info

Publication number: CN116874285B
Application number: CN202310761208.4A
Authority: CN
Inventors: 李龙; 李培刚
Original assignee: Beijing Gachuang Technology Co ltd
Current assignee: Beijing Gachuang Technology Co ltd
Priority date: 2023-06-26
Filing date: 2023-06-26
Publication date: 2025-01-28
Anticipated expiration: 2043-06-26
Also published as: CN116874285A

Abstract

The present invention provides a crucible for growing gallium oxide crystals and a preparation method thereof. The crucible is made of raw materials including aluminum oxide, zircon sand and magnesia sand; wherein the mass ratio of aluminum oxide, zircon sand and magnesia sand is (1-3):(2-4):(3-5), and the refractoriness of the crucible is ≥1900°C. The present invention adopts an iridium-free technical route, which can not only avoid high-temperature oxidation of the crucible and chemical reaction with the melt, but also reduce the use of precious metal iridium by using an oxide crucible instead of an iridium gold crucible, making the gallium oxide growth process not only simpler and more controllable, but also lower in cost, and has greater industrialization prospects.

Description

Crucible for growing gallium oxide crystal and preparation method thereof

Technical Field

The invention relates to the technical field of semiconductor material preparation, in particular to a crucible for growing gallium oxide crystals and a preparation method thereof.

Background

The forbidden bandwidth of the gallium oxide semiconductor is about 4.9eV, and the breakdown electric field strength is as high as 8MV/cm, which is far higher than that of semiconductor materials such as silicon, silicon carbide, gallium nitride and the like. The larger the forbidden bandwidth, the higher the voltage and the higher the temperature the device can bear, and the larger the output power of the device. Meanwhile, the larger the forbidden bandwidth is, the higher the chemical stability of the device is, so that the power device can work in a worse environment, and the stability and reliability of the system are greatly improved. In addition, the theoretical loss of gallium oxide is 1/6 of silicon carbide and 1/3 of gallium nitride, namely, the loss is reduced by 86% on the basis that the loss of SiC is reduced by 86% compared with Si. Because of the advantages of excellent physical property, high thermal stability and chemical stability, low energy consumption, good controllability, low cost and the like, the solar-blind ultraviolet light conductive electrode has great potential in the aspects of manufacturing high-voltage, high-temperature and high-power electronic devices, solar-blind ultraviolet light electronic devices, ultraviolet transparent conductive electrodes and the like.

The choice of crucible material is determined by the crystal being grown and its properties in the molten state. The crucible is in direct contact with the grown crystal and its melt and has a significant impact on the heat transfer characteristics of the crystal growth process. Therefore, the choice of crucible material is one of the controlling factors of whether the crystal growth process can be achieved and the quality of the crystal structure. The melting point of gallium oxide material is higher (about 1800 ℃), the crucible material for growing gallium oxide crystals is mainly iridium metal at present, crystal growth can be carried out under the conditions of 1800 ℃ and a certain oxygen atmosphere, but the iridium metal is expensive and is more than 3 times of the gold price, the cost is high, the equipment quantity is difficult to expand from the aspect of mass production to increase the productivity, the iridium metal depends on import, and the supply chain has great risks.

The matters in the background section are only those known to the inventors and do not, of course, represent prior art in the field.

Disclosure of Invention

In order to solve the problems of high-temperature oxidation and crucible cost in gallium oxide crystal growth, the invention provides a crucible for growing gallium oxide crystals and a preparation method thereof.

The crucible for growing gallium oxide crystals is prepared from raw materials including aluminum oxide, zircon sand and magnesia;

The mass ratio of the alumina to the zircon sand to the magnesia is (1-3), the mass ratio of the alumina to the zircon sand to the magnesia is (2-4), the mass ratio of the alumina to the zircon sand to the magnesia is (3-5), and the refractoriness of the crucible is not less than 1900 ℃.

In some embodiments of the invention, the crucible has a thermal conductivity of 7.0 to 8.0 at a temperature of 1000 to 1800 ℃, a linear expansion coefficient of 9.0 to 9.5 x 10 ^-6/°c, a heat capacity of 700 to 800j/kg·k, and a bulk density of 3.8 to 4.2g/cm ³.

In some embodiments of the invention, the crucible has a normal temperature compressive strength of 60-65 MPa,0.1MPa, a load softening temperature of greater than 1700 ℃, and a linear change rate of-0.5-1.6%.

In some embodiments of the invention, the crucible is fired at a temperature of 1750 to 1850 ℃.

The preparation method of the crucible for growing gallium oxide crystals provided by the invention comprises the following steps:

uniformly mixing zircon sand and magnesia to obtain a mixture;

reacting the alumina ultrafine powder with the mixture to obtain a reactant;

Uniformly mixing the reactant, the filler and the auxiliary materials, and then pouring the mixture into a die for compression molding to obtain a blank;

Curing, calcining and cooling the blank in sequence to obtain the crucible;

the mass ratio of the alumina ultrafine powder to the zircon sand to the magnesia is (1-3), the mass ratio of the alumina ultrafine powder to the zircon sand to the magnesia is (2-4), the mass ratio of the alumina ultrafine powder to the zircon sand to the magnesia is (3-5), and the refractoriness of the crucible is more than or equal to 1900 ℃.

In some embodiments of the invention, the curing temperature is 150-160 ℃ and the curing time is 3-4 hours.

In some embodiments of the invention, the calcination temperature is 1750 to 1850 ℃ and the calcination time is 2 to 3 hours.

In some embodiments of the invention, the alumina micropowder has a particle size of 5 to 10 microns, and the zircon sand and the magnesite have a particle size of 100 to 200 microns.

In some embodiments of the invention, uniformly mixing zircon sand and magnesia to obtain a mixture comprises:

Sequentially adding the zircon sand and the magnesia into a high-speed stirrer, and stirring at the rotating speed of 800-1000 r/min for 45-60 min to obtain the mixture.

In some embodiments of the invention, reacting the alumina micropowder with the mixture comprises:

And reacting the alumina ultrafine powder with the mixture at the temperature of 250-300 ℃ for 50-60 min to obtain the reactant.

According to the invention, an iridium-free technical route is adopted, so that high-temperature oxidation of the crucible and chemical reaction with a melt can be avoided, and the oxide crucible is used for replacing the iridium crucible, so that the use of noble metal iridium is reduced, the gallium oxide growth process is simpler and controllable, the cost is lower, and the method has a larger industrialization prospect.

Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

Drawings

The accompanying drawings, which are included to provide a further understanding of the disclosure, illustrate and explain the exemplary embodiments of the disclosure and together with the description serve to explain the disclosure, and do not constitute an undue limitation on the disclosure.

Fig. 1 is a process flow diagram of preparing a crucible according to an embodiment of the present invention.

Detailed Description

Hereinafter, only certain exemplary embodiments are briefly described. As will be recognized by those of skill in the pertinent art, the described embodiments may be modified in various different ways without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not as restrictive.

The following disclosure provides many different embodiments, or examples, for implementing the invention. In order to simplify the present disclosure, components and arrangements of specific examples are described below. They are, of course, merely examples and are not intended to limit the invention. Furthermore, the present invention may repeat reference numerals and/or letters in the various examples, which are for the purpose of brevity and clarity, and which do not themselves indicate the relationship between the various embodiments and/or arrangements discussed. In addition, the present invention provides examples of various specific processes and materials, but one of ordinary skill in the art will recognize the application of other processes and/or the use of other materials.

Furthermore, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present invention and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

In view of the measurements in question and the errors associated with the particular amounts of the measurements (i.e., limitations of the measurement system), as used herein "about" or "approximately" includes the stated values and is intended to be within the acceptable range of deviation from the particular values as determined by one of ordinary skill in the art. For example, "about" may mean within one or more standard deviations, or within ±30%, ±20%, ±10% or ±5% of the stated value.

The following detailed description of specific embodiments of the invention is provided in connection with the accompanying drawings and examples in order to provide a better understanding of the aspects of the invention and advantages thereof. However, the following description of specific embodiments and examples is for illustrative purposes only and is not intended to be limiting of the invention.

The gallium oxide crystal has a thermal conductivity of about 12.0 at a temperature of 1000-1800 ℃, a linear expansion coefficient of about 9.5X10- ^-6/°c, a liquid state of about 720J/kg-K (solid state heat capacity of about 560J/kg-K)), a bulk density of about 5.8g/cm ³, and a melting point of about 1800 ℃. The existing crucibles for preparing gallium oxide crystals are basically iridium crucibles, the thermal conductivity of iridium metal at the temperature of 1000-1800 ℃ is about 147.0, the linear expansion coefficient is about 6.5X10- ^-6/°c, the heat capacity is about 130J/kg-K, the volume density is about 22.6g/cm ³, and the melting point is about 2450 ℃. As mentioned before, iridium crucibles are very costly and difficult to produce on a large scale, with a significant risk to the supply chain. Moreover, iridium metals have a too high heat conductivity that is detrimental to crystal growth and generally have chemical stability.

The main raw materials of the crucible provided by the invention are alumina, zircon sand and magnesia, wherein the mass ratio of the alumina to the zircon sand to the magnesia is about (1-3): (2-4): (3-5). The crucible provided by the invention has the advantages that the refractoriness can be more than or equal to 1900 ℃, the thermal stability is good, the crucible hardly has chemical reaction with gallium oxide, and the growth of crystals is very facilitated. According to the invention, an iridium-free technical route is adopted, so that high-temperature oxidation of the crucible and chemical reaction with a melt can be avoided, and the oxide crucible is used for replacing the iridium crucible, so that the use of noble metal iridium is reduced, the gallium oxide growth process is simpler and controllable, the cost is lower (the comprehensive cost is about 1/100 of the cost of the current iridium crucible), and the method has a larger industrialization prospect.

In some embodiments of the invention, the crucible has a thermal conductivity of about 7.0 to about 8.0 at a temperature of 1000 to 1800 ℃, a linear expansion coefficient of about 9.0 to about 9.5X10 ^-6/°c, a heat capacity of about 700 to 800j/kg·k, a bulk density of about 3.8 to about 4.2g/cm ³, and a melting point of about 1900 to 2000 ℃. The thermal expansion coefficient of the crucible is slightly smaller than that of the gallium oxide crystal, so that larger compressive stress is not formed on the crystal in the growth process of the gallium oxide crystal, and the growth quality of the gallium oxide crystal is improved. The crucible has heat conduction capacity matched with gallium oxide crystals, and is beneficial to heating the melt in a heating zone and cooling the crystals in a cooling zone. Whether the thermal conductivity, linear expansion coefficient, or heat capacity are very close to those of gallium oxide, this is very advantageous for high quality control of gallium oxide crystal growth. The heat capacity of the crucible provided by the invention is 5 times that of the metal iridium, the heat preservation property is good, the heat dissipation in the long-time crystal growth process can be reduced, the heat efficiency is improved, and the purpose of saving energy is achieved.

In some embodiments of the invention, the crucible has a normal temperature compressive strength of about 60 to 65MPa, a load softening temperature of 0.1MPa greater than 1700 ℃, and a line change rate of about-0.5 to 1.6%. The crucible has higher melting point and high-temperature strength, has higher chemical stability, can still keep enough strength at the growth temperature of the crystal, can not be decomposed or oxidized under the high-temperature oxygen atmosphere, and basically does not react with the crystal or melt.

Fig. 1 shows a method for preparing the crucible according to an embodiment of the invention, which includes the following steps S10 to S40.

And S10, uniformly mixing zircon sand and magnesia to obtain a mixture.

Optionally, the grain sizes of the zircon sand and the magnesia are 100-200 microns.

In some embodiments of the invention, the step may be to sequentially add zircon sand and magnesia into a high-speed mixer, and mix for 45-60 min at a rotational speed of 800-1000 r/min to obtain a mixture.

And S20, reacting the alumina ultrafine powder with the mixture to obtain a reactant.

Wherein the mass ratio of the alumina to the zircon sand to the magnesia is about (1-3): (2-4): (3-5).

Optionally, the particle size of the alumina ultrafine powder is 5-10 microns. The 5-10 micron alumina ultrafine powder is matched with 100-200 micron zircon sand and magnesia, so that the density of the prepared crucible is high, and the heat resistance and the high-temperature strength of the crucible are improved.

In some embodiments of the present invention, the step includes reacting an alumina micropowder with the mixture at a temperature of 250-300 ℃ for 50-60 minutes to obtain a reactant.

And S30, uniformly mixing the reactant, the filler and the auxiliary materials, and pouring the mixture into a die for compression molding to obtain a blank.

Optionally, the filler is kaolin, and the auxiliary material is clay.

Optionally, the pressure is 10-30 MP during compression molding.

And S40, curing, calcining and cooling the blank in sequence.

Cooling to room temperature to obtain the oxidation-resistant and high-temperature-resistant crucible.

The preparation method provided by the invention is simple and convenient, and the prepared crucible has excellent performance and low cost.

The invention will now be described with reference to specific examples. The values of the process conditions taken in the examples below are exemplary and can be obtained in the ranges indicated in the foregoing summary, and for process parameters not specifically identified, reference may be made to conventional techniques. The detection methods used in the examples below are all conventional in the industry. Reagents and apparatus used in the technical scheme provided by the invention are available from conventional channels or markets unless otherwise specified.

Example 1

The crucible for growing gallium oxide crystals is prepared according to the embodiment, and the specific process is as follows:

Sequentially adding 20 parts of zircon sand and 50 parts of magnesia into a high-speed stirrer, wherein the stirring speed is about 1000r/min, and the stirring time is about 45min, so as to obtain a mixture.

The mixture and 25 parts of alumina micropowder were fed into a reaction vessel at a reaction temperature of about 250 ℃ for a reaction time of about 60 minutes to give a reactant.

The reactants, 3 parts of kaolin and 2 parts of clay were poured into a crucible mold and pressed by a press at a pressure of about 15 MPa. And (3) placing the formed crucible in a curing room for curing at a curing temperature of about 150 ℃ for about 3 hours, then placing the crucible in a high-temperature calciner for drying and calcining at a calcining temperature of about 1750 ℃ for about 3 hours, and then cooling to obtain the crucible.

Wherein the alumina micropowder has an average particle size of about 5 microns and the zircon and magnesia have average particle sizes of about 100 microns and 120 microns, respectively.

The crucible performance index is shown in table 1. The crucible thus obtained was used for growing gallium oxide crystals at a growth rate of about 10mm/h.

Example 2

Sequentially adding 30 parts of zircon sand and 50 parts of magnesia into a high-speed stirrer, wherein the stirring speed is about 800r/min, and the stirring time is about 60min, so as to obtain a mixture.

The mixture and 15 parts of alumina ultrafine powder were fed into a reaction vessel at a reaction temperature of about 300℃for a reaction time of about 55 minutes to obtain a reaction product.

The reactants, 3 parts of kaolin and 2 parts of clay were poured into a crucible mold and pressed by a press at a pressure of about 20 MPa. And (3) placing the formed crucible in a curing room for curing at the curing temperature of about 160 ℃ for about 3 hours, then placing the crucible in a high-temperature calciner for drying and calcining at the calcining temperature of about 1850 ℃ for about 2.5 hours, and then cooling to obtain the crucible.

Wherein the alumina micropowder has an average particle size of about 10 microns and the zircon and magnesia have average particle sizes of about 150 microns and 140 microns, respectively.

The crucible performance index is shown in table 1. The crucible thus obtained was used for growing gallium oxide crystals at a growth rate of about 15mm/h.

Example 3

sequentially adding 30 parts of zircon sand and 40 parts of magnesia into a high-speed stirrer, wherein the stirring speed is about 900r/min, and the stirring time is about 50min, so as to obtain a mixture.

The mixture and 25 parts of alumina micropowder were fed into a reaction kettle at a reaction temperature of about 270 ℃ for a reaction time of about 50 minutes to give a reactant.

The reactants, 3 parts of kaolin and 2 parts of clay were poured into a crucible mold and pressed by a press at a pressure of about 30 MPa. And (3) placing the formed crucible in a curing room for curing at a curing temperature of about 155 ℃ for about 3.5 hours, then placing the crucible in a high-temperature calciner for drying and calcining at a calcining temperature of about 1800 ℃ for about 2.2 hours, and then cooling to obtain the crucible.

Wherein the alumina micropowder has an average particle size of about 13 microns and the zircon and magnesia have average particle sizes of about 180 microns and 190 microns, respectively.

Comparative example 1

This comparative example prepares a crucible for growing gallium oxide crystals, and the specific procedure is as follows:

95 parts of zirconium dioxide, 3 parts of kaolin and 2 parts of clay are poured into a crucible mold and pressed by a press at a pressure of about 15 MPa. And (3) placing the formed crucible in a curing room for curing at a curing temperature of about 150 ℃ for about 3 hours, then placing the crucible in a high-temperature calciner for drying and calcining at a calcining temperature of about 1750 ℃ for about 3 hours, and then cooling to obtain the crucible.

Wherein the zirconium dioxide has an average particle size of about 150 microns.

The crucible performance index is shown in table 1. The prepared crucible is used for growing gallium oxide crystals, the reaction layer grows on the surface of the crucible, the thickness is close to 2mm, and the crucible is obviously softened along with heating, so that the gallium oxide crystals cannot be grown normally in the follow-up process.

Comparative example 2

95 parts of magnesium oxide, 3 parts of kaolin and 2 parts of clay are poured into a crucible mold and pressed by a press at a pressure of about 20 MPa. And (3) placing the formed crucible in a curing room for curing at a curing temperature of about 150 ℃ for about 3 hours, then placing the crucible in a high-temperature calciner for drying and calcining at a calcining temperature of about 1750 ℃ for about 3 hours, and then cooling to obtain the crucible.

Wherein the magnesium oxide has an average particle size of about 180 microns.

The crucible performance index is shown in table 1. The prepared crucible is used for growing gallium oxide crystals, and the prepared crystals are found to have poor quality and low crystal yield.

Comparative example 3

45 parts of zircon sand and 50 parts of magnesite sand are sequentially added into a high-speed stirrer, the stirring speed is about 900r/min, and the stirring time is about 50min, so that a mixture is obtained.

The mixture, 3 parts of kaolin and 2 parts of clay were poured into a crucible mold and pressed by a press at a pressure of about 30 MPa. And (3) placing the formed crucible in a curing room for curing at a curing temperature of about 155 ℃ for about 3.5 hours, then placing the crucible in a high-temperature calciner for drying and calcining at a calcining temperature of about 1800 ℃ for about 2.2 hours, and then cooling to obtain the crucible.

Wherein the zircon sand and the magnesite sand have average grain sizes of about 180 microns and 190 microns, respectively.

The crucible performance index is shown in table 1. The prepared crucible is used for growing gallium oxide crystals, the reaction layer grows on the surface of the crucible, the thickness is close to 1mm, and the crucible is softened to a certain extent along with heating, so that the gallium oxide crystals cannot be grown normally in the follow-up process.

Comparative example 4

50 parts of zircon sand and 45 parts of alumina ultrafine powder are fed into a reaction kettle, the reaction temperature is about 270 ℃, and the reaction time is about 50 minutes, so as to obtain a reactant.

Wherein the alumina micropowder has an average particle size of about 13 microns and the zircon sand has an average particle size of about 180 microns.

The crucible performance index is shown in table 1. The prepared crucible is used for growing gallium oxide crystals, the reaction layer grows on the surface of the crucible, the thickness of the reaction layer is close to 1.5mm, and the crucible is softened to a certain extent along with heating, so that the gallium oxide crystals cannot be grown normally in the follow-up process.

Comparative example 5

50 parts of magnesite and 45 parts of alumina ultrafine powder are fed into a reaction kettle, the reaction temperature is about 270 ℃, and the reaction time is about 50 minutes, so that a reactant is obtained.

Wherein the alumina micropowder has an average particle size of about 13 microns and the magnesia has an average particle size of about 190 microns.

The crucible performance index is shown in table 1. The prepared crucible is used for growing gallium oxide crystals, and the prepared crystals are found to have poor quality and lower crystal yield.

Comparative example 6

This comparative example differs from example 3 only in that the calcination temperature is 1500 ℃.

The crucible performance index is shown in table 1. The prepared crucible was used for growing gallium oxide crystals, and the quality of the prepared crystals was found to be poor.

Comparative example 7

This comparative example differs from example 3 only in that the calcination temperature is 1950 ℃.

TABLE 1

As is clear from comparative example 1, the growth of gallium oxide crystals was carried out at 1800℃with zirconium dioxide having a high melting point as a crucible material, zirconium dioxide was chemically reacted with gallium oxide melt (reaction layer thickness was close to 2 mm), and the crucible was significantly softened, so that gallium oxide crystals could not be grown normally.

As is apparent from comparative example 2, since the crucible is directly manufactured from magnesium oxide having a high melting point, since the magnesium oxide material has a larger expansion coefficient than gallium oxide, the crucible gives a certain compressive stress to the grown gallium oxide crystal when the gallium oxide crystal is cooled, solidified and crystallized, thereby increasing defects of the crystal, reducing the quality of the crystal, and even damaging the growth of the crystal.

As is clear from comparative example 3, the crucible made of zircon sand and magnesia still reacted with the gallium oxide melt to some extent (the thickness of the reaction layer exceeded 1 mm), and the crucible softened to some extent, so that gallium oxide crystals could not be grown normally.

As is clear from comparative example 4, the crucible made of zircon sand and alumina still reacted with the gallium oxide melt to some extent (the thickness of the reaction layer exceeded 1.5 mm), and the crucible softened to some extent, so that gallium oxide crystals could not be grown normally.

As is clear from comparative example 5, the crucible made of magnesia and alumina does not substantially react with the gallium oxide melt, but since the expansion coefficient of the crucible is larger than that of gallium oxide, the crucible gives a certain compressive stress to the grown gallium oxide crystal when the gallium oxide crystal is solidified and crystallized, so that defects of the crystal are increased, and thus gallium oxide crystal of high quality cannot be grown normally.

As is clear from comparative example 6, the calcination temperature is lower than 1750 ℃, and the expansion coefficient of the prepared crucible is larger than that of gallium oxide, so that the crystal is subjected to compressive stress during solidification and crystallization of gallium oxide, thereby increasing growth defects and reducing the quality of crystal growth.

As is clear from comparative example 7, the calcination temperature was higher than 1850 ℃, zircon sand and magnesia were significantly chemically reacted, and the magnesium content in the crucible was reduced and lower than that in example 3, so that the prepared crucible still reacted with gallium oxide melt to some extent (the thickness of the reaction layer exceeded 1 mm), and the crucible was softened to some extent, and gallium oxide crystals were not normally grown.

The crucible provided by the invention has low cost and is very suitable for growth of gallium oxide crystals.

It is apparent that the above examples are only illustrative of the present invention and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. And obvious variations or modifications thereof are contemplated as falling within the scope of the present invention.

Claims

1. A method for preparing a crucible for growing gallium oxide crystals, comprising:

Mixing zircon sand and magnesia sand uniformly to obtain a mixture;

reacting the ultrafine aluminum oxide powder with the mixture to obtain a reactant;

The reactant is mixed evenly with a filler and an auxiliary material, and then poured into a mold for compression molding to obtain a blank, wherein the filler is kaolin and the auxiliary material is clay;

The blank is sequentially cured, calcined and cooled to obtain the crucible;

Wherein, the mass ratio of the ultrafine alumina powder, the zirconium sand and the magnesia sand is (1-3): (2-4): (3-5), and the refractoriness of the crucible is ≥ 1900°C;

The particle size of the ultrafine alumina powder is 5-10 microns, and the particle size of the zircon sand and the magnesia sand is 100-200 microns;

The calcination temperature is 1750~1850℃, and the calcination time is 2~3h.

2. The preparation method according to claim 1, characterized in that the curing temperature is 150-160°C and the curing time is 3-4h.

3. The preparation method according to claim 1, characterized in that the zircon sand and magnesia sand are mixed uniformly to obtain the mixture comprising:

The zircon sand and the magnesia sand are sequentially added into a high-speed mixer, and stirred at a speed of 800-1000 r/min for 45-60 min to obtain the mixture.

4. The preparation method according to claim 1, characterized in that the ultrafine aluminum oxide powder and the mixture are reacted to obtain the reactant comprising:

The ultrafine alumina powder and the mixture are reacted at a temperature of 250-300° C. for 50-60 minutes to obtain the reactant.

5. A crucible for growing gallium oxide crystals, characterized in that it is made by the preparation method described in any one of claims 1 to 4.

The crucible according to claim 5, characterized in that the crucible has a thermal conductivity of 7.0-8.0 at a temperature of 1000-1800°C, a linear expansion coefficient of 9.0-9.5×10 ^-6 /°C, a heat capacity of 700-800 J/kg·K, and a bulk density of 3.8-4.2 g/cm ³ .

7. The crucible according to claim 5, characterized in that the room temperature compressive strength of the crucible is 60-65 MPa, the softening temperature under load of 0.1 MPa is greater than 1700°C, and the linear change rate is -0.5-1.6%.