A method for preparing large-primitive-sphere low-sodium alpha-alumina powder by microwave low-temperature calcination and its application

Abstract

The application relates to the technical field of alumina powder preparation, and discloses a microwave low-temperature calcination preparation method of large-primitive-crystal low-sodium spherical alpha-alumina powder, which comprises the following steps: (1) mixing industrial alumina powder and a composite mineralizer, and then performing ball milling by using grinding balls to prepare a ball-milled powder; (2) performing microwave calcination on the ball-milled powder prepared in the step (1) to prepare a calcined substance; and (3) performing ball milling on the calcined substance prepared in the step (2) to prepare the large-primitive-crystal low-sodium spherical alpha-alumina powder. By optimizing the production process, optimizing the composition and the dosage of the composite mineralizer and adopting the microwave calcination method, the large-primitive-crystal low-sodium spherical alpha-alumina powder can be obtained by low-temperature (less than 1000 DEG C) calcination, the calcination time can be shortened, and the production cost is lower compared with the existing high-temperature calcination technology.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of alumina powder preparation, and particularly relates to a microwave low-temperature calcination preparation method of large-primitive-crystal low-sodium spherical alpha-alumina powder and application thereof.

BACKGROUND

[0002] At present, there are few materials as heat-conducting and electrically insulating fillers, and common ones are aluminum nitride (AlN, thermal conductivity 320 W·m -1 ·K -1 ), silicon carbide (SiC, thermal conductivity 270 W·m -1 ·K -1 ), beryllium oxide (BeO, thermal conductivity 219 W·m -1 ·K -1 ), magnesium oxide (MgO thermal conductivity 36 W·m -1 ·K -1 ), alpha-alumina (Al2O3, thermal conductivity 30 W·m -1 ·K -1 ), and the like.

[0003] Compared with traditional alpha-alumina heat-conducting materials, the large-primitive-crystal low-sodium spherical alpha-alumina powder has the advantages of large single-crystal size, spherical crystal morphology, low sodium content, reasonable particle size distribution, good dispersibility, high thermal conductivity, low electrical conductivity, acid and alkali resistance, high temperature resistance, and the like, and can be widely applied to the fields of heat-conducting plastics, high-thermal-conductivity gels, high-thermal-conductivity gaskets, electronic packaging, and the like.

[0004] At present, the production process of alpha-alumina powder mainly has: sol-emulsion-gel method, melting jet method, high temperature calcination method, homogeneous precipitation method, template method, drop ball method, etc., wherein, the sol-emulsion-gel method, the melting jet method, the high temperature calcination method can prepare the spherical / spherical alpha-alumina powder with the single crystal grain diameter of micron level. The sol-emulsion-gel method increases the difficulty of powder separation and drying due to the use of organic solvent and surfactant and the like auxiliary materials, and the product is easy to agglomerate, and it is difficult to realize large-scale production;The melting jet method can obtain the spherical alpha-alumina particles with high sphericity and large particle size by directly melting and spheroidizing the solid aluminum powder or alumina powder by plasma flame, but the pores defects are formed in the particles, which reduces the density and thermal conductivity of the particles;The high temperature calcination method needs to be calcined at 1300 DEG C or more for 10 hours or more, and specific mineralizer is added, so as to produce the spherical alpha-alumina powder, and the energy consumption is high, and the production cost is high. SUMMARY

[0005] In view of the defects of the prior art, the purpose of the present application is to provide a microwave low-temperature calcination preparation method of large primary crystal low-sodium spherical alpha-alumina powder, which uses ordinary alumina as raw material, and through the addition of a composite mineralizer, it is sequentially subjected to ball milling, microwave calcination (less than 1000 DEG C) and ball milling, to obtain a large primary crystal low-sodium spherical alpha-alumina powder product with a purity of > 99%, a single crystal grain diameter of 20-30 μm, a sodium content of < 0.02wt%, and a sphericity of > 80%.

[0006] In order to achieve the above technical purpose, the present application adopts the following technical scheme:

[0007] A microwave low-temperature calcination preparation method of large primary crystal low-sodium spherical alpha-alumina powder, comprising the following steps:

[0008] (1) mixing industrial alumina powder and composite mineralizer, and then ball milling at a temperature of 62-73 DEG C for 3-5 h to obtain a ball milled powder;

[0009] (2) microwave calcining the ball milled powder prepared in step (1), controlling the heating rate to be 6-10 DEG C / min, and calcining at a calcining temperature of 850-980 DEG C for 5-10 h to obtain a calcined product;

[0010] (3) ball milling the calcined product prepared in step (2) for 3-6 h to obtain a large primary crystal low-sodium spherical alpha-alumina powder.

[0011] The technical principle of the present application is:

[0012] The low-sodium alpha-alumina powder is obtained by using calcium dihydrogen phosphate and magnesium bicarbonate mineralizer to remove sodium impurities, so that the target of Na2O<0.02wt% is achieved.

[0013] The industrial alumina crystal is fully activated by the heat effect and non-heat effect of microwaves, and the growth of alpha-alumina primary crystal is promoted by the cooperation of aluminum stearate and sodium fatty alcohol polyoxyethylene ether sulfate.

[0014] The hard agglomeration formed when the industrial alumina powder is transformed from a transition phase to an alpha-alumina phase during microwave calcination is avoided by using polyethylene oxide, which plays a role in auxiliary isolation of dispersed phases, so that the alpha-alumina powder particles are separated from each other and the particle size is relatively uniform.

[0015] The use of triethanolamine plays a role in assisting grinding, which can promote the rapid size reduction of industrial alumina during ball milling and shorten the time to obtain the target size.

[0016] The use of barium oxide and terbium oxide can synergistically accelerate the growth of alpha-alumina single crystals, and also improve the sphericity of alpha-alumina powder, achieving the target of controlling sphericity>80%.

[0017] The use of magnesium bicarbonate and terbium oxide synergistically regulates the primary crystal size of alpha-alumina powder, achieving the target of controlling the average particle size of alpha-alumina powder>20μm with narrow particle size distribution.

[0018] Further, the sodium content of the industrial alumina powder in step (1) is 0.35-0.5wt%, and the average particle size is 50.3-100.6μm.

[0019] Further, the mass ratio of the industrial alumina powder and the composite mineralizer in step (1) is (92.4-105.3):(8.6-12.2).

[0020] Further, the grinding balls in step (1) or step (3) are 99 ceramic alumina balls, and the diameter of the grinding balls is 4-8mm.

[0021] Further, the rotation speed of ball milling in step (1) is 300-400r / min.

[0022] Further, the ball-to-material ratio in step (1) is 5-6:1.

[0023] Further, the rotation speed of ball milling in step (3) is 500-600r / min.

[0024] Further, the ball-to-material ratio in step (3) is 3.3-4:1.

[0025] The present application has the following advantages:

[0026] (1) The present application can obtain large-primitive low-sodium spherical alpha-alumina powder by optimizing the production process and using one-step calcination method, compared with the prior art which uses two-step calcination method to obtain large-primitive low-sodium spherical alpha-alumina powder, the production process of the present application is more simple.

[0027] (2) The present application can obtain large-primitive low-sodium spherical alpha-alumina powder by optimizing the production process, optimizing the composition and dosage of composite mineralizer, and using microwave calcination method, which can realize low-temperature (less than 1000℃) calcination, shorten the calcination time, and reduce the production cost compared with the prior high-temperature calcination technology.

[0028] (3) The production process of the present application does not add halide, boride and other mineralizers, which can realize the controllable growth of primitive crystals and has no pollution and corrosion to the production equipment, which can greatly reduce the production cost of alpha-alumina powder and facilitate large-scale production.

DETAILED DESCRIPTION

[0029] In order to better understand the present application, the following examples are used for illustration, which belong to the protection scope of the present application, but do not limit the protection scope of the present application.

[0030] In the embodiment of the present application, the preparation method of the large-primitive low-sodium spherical alpha-alumina powder comprises the following steps:

[0031] (1) After mixing industrial alumina powder and composite mineralizer, grinding balls are used for ball milling at a temperature of 62-73℃ for 3-5h to prepare ball milled powder, the sodium content of the industrial alumina powder is 0.35-0.5wt%, and the average particle size is 50.3-100.6μm; the mass ratio of the industrial alumina powder and the composite mineralizer is (92.4-105.3):(8.6-12.2); the composite mineralizer is composed of calcium dihydrogen phosphate, aluminum stearate, polyethylene oxide, fatty alcohol polyoxyethylene ether sodium sulfate, triethanolamine, barium oxide, magnesium bicarbonate, and terbium oxide with a mass ratio of (3.1-5.4):(0.6-1.1):(2.3-2.8):(0.3-0.7):(1-1.5):(0.4-0.8):(0.2-0.4):(0.3-0.5); the grinding ball is 99 porcelain alumina ball, the diameter of the grinding ball is 4-8mm, the rotation speed of the ball mill is 300-400r / min, and the ball-to-material ratio is 5-6:1;

[0032] (2) The ball milled powder prepared in step (1) is subjected to microwave calcination, the heating rate is controlled at 6-10℃ / min, and the calcination temperature is 850-980℃, and the calcination time is 5-10h to prepare calcined material;

[0033] (3) the calcined product prepared in step (2) is ball milled for 3-6 hours to prepare a large-crystal low-sodium spherical α-alumina powder, the ball milling uses 99 ceramic alumina balls, the ball milling speed is 500-600 r / min, the ball-to-material ratio is 3.3-4:1, and the diameter of the ball milling balls is 4-8 mm.

[0034] The application will be described in more detail by way of specific examples.

[0035] Example 1

[0036] A microwave low-temperature calcination preparation method of a large-crystal low-sodium spherical α-alumina powder, comprising the following steps:

[0037] (1) industrial alumina powder and a composite mineralizer are mixed, and then ball milling is performed at a temperature of 63 ℃ for 5 hours using ball milling balls to prepare a ball-milled powder, the sodium content of the industrial alumina powder is 0.37 wt%, and the average particle size is 82.5 μm; the mass ratio of the industrial alumina powder to the composite mineralizer is 92.7:8.9; the composite mineralizer is composed of calcium dihydrogen phosphate, aluminum stearate, polyethylene oxide, fatty alcohol polyoxyethylene ether sodium sulfate, triethanolamine, barium oxide, magnesium bicarbonate, and terbium oxide at a mass ratio of 3.5:0.7:2.5:0.3:1:0.4:0.2:0.3; the ball milling balls are 99 ceramic alumina balls, the diameter of the ball milling balls is 5 mm, the ball milling speed is 300 r / min, and the ball-to-material ratio is 5.2:1;

[0038] (2) the ball-milled powder prepared in step (1) is subjected to microwave calcination, the heating rate is controlled to be 7 ℃ / min, the calcination temperature is 860 ℃, and the calcination time is 8 hours to prepare a calcined product;

[0039] (3) the calcined product prepared in step (2) is ball milled for 5 hours to prepare a large-crystal low-sodium spherical α-alumina powder, the ball milling uses 99 ceramic alumina balls, the ball milling speed is 500 r / min, the ball-to-material ratio is 3.3:1, and the diameter of the ball milling balls is 5 mm.

[0040] Example 2

[0041] A microwave low-temperature calcination preparation method of a large-crystal low-sodium spherical α-alumina powder, comprising the following steps:

[0042] (1) mixing industrial alumina powder and composite mineralizer, then ball milling at 66℃ for 4h using grinding ball to obtain ball-milled powder, the sodium content of the industrial alumina powder is 0.41wt%, the average particle size is 85.6μm; the mass ratio of the industrial alumina powder to the composite mineralizer is 95.1:9.2; the composite mineralizer is composed of calcium dihydrogen phosphate, aluminum stearate, polyethylene oxide, fatty alcohol polyoxyethylene ether sodium sulfate, triethanolamine, barium oxide, magnesium bicarbonate, terbium oxide with a mass ratio of 3.7:0.8:2.3:0.4:1.1:0.4:0.2:0.3; the grinding ball is 99 porcelain alumina ball, the diameter of the grinding ball is 4mm, the rotation speed of the ball mill is 400r / min, and the ball-to-material ratio is 5.5:1;

[0043] (2) calcining the ball-milled powder obtained in step (1) in air at a heating rate of 6℃ / min, a calcination temperature of 895℃ and a calcination time of 7h to obtain a calcined product;

[0044] (3) ball milling the calcined product obtained in step (2) for 4h to obtain large-crystal low-sodium spherical α-alumina powder, the grinding ball used in the ball milling is 99 porcelain alumina ball, the rotation speed of the ball mill is 500r / min, the ball-to-material ratio is 3.5:1, and the diameter of the grinding ball is 4mm.

[0045] Example 3

[0046] A microwave low-temperature calcination method for preparing large-crystal low-sodium spherical α-alumina powder, comprising the following steps:

[0047] (1) mixing industrial alumina powder and composite mineralizer, then ball milling at 68℃ for 3.5h using grinding ball to obtain ball-milled powder, the sodium content of the industrial alumina powder is 0.45wt%, the average particle size is 88.3μm; the mass ratio of the industrial alumina powder to the composite mineralizer is 97.6:10.2; the composite mineralizer is composed of calcium dihydrogen phosphate, aluminum stearate, polyethylene oxide, fatty alcohol polyoxyethylene ether sodium sulfate, triethanolamine, barium oxide, magnesium bicarbonate, terbium oxide with a mass ratio of 3.9:0.9:2.4:0.5:1.2:0.6:0.3:0.4; the grinding ball is 99 porcelain alumina ball, the diameter of the grinding ball is 7mm, the rotation speed of the ball mill is 400r / min, and the ball-to-material ratio is 5.8:1;

[0048] (2) calcining the ball-milled powder obtained in step (1) in air at a heating rate of 9℃ / min, a calcination temperature of 930℃ and a calcination time of 7h to obtain a calcined product;

[0049] (3) the calcined product prepared in step (2) is ball milled for 4.5 h to obtain the large-crystal low-sodium spherical alpha-alumina powder, the ball milling uses 99 ceramic alumina balls, the rotation speed of the ball milling is 550 r / min, the ball-to-material ratio is 3.8:1, and the diameter of the ball is 7 mm.

[0050] Example 4

[0051] A microwave low-temperature calcination method for preparing a large-crystal low-sodium spherical alpha-alumina powder, comprising the following steps:

[0052] (1) industrial alumina powder and a composite mineralizer are mixed, and then ball milling is performed at a temperature of 69℃ for 4.5 h to obtain a ball-milled powder, the sodium content of the industrial alumina powder is 0.43 wt%, and the average particle size is 88.2 μm; the mass ratio of the industrial alumina powder to the composite mineralizer is 100.1:10.6; the composite mineralizer is composed of calcium dihydrogen phosphate, aluminum stearate, polyethylene oxide, fatty alcohol polyoxyethylene ether sodium sulfate, triethanolamine, barium oxide, magnesium bicarbonate, and terbium oxide at a mass ratio of 4.1:0.9:2.4:0.6:1.3:0.6:0.3:0.4; the ball milling uses 99 ceramic alumina balls, the diameter of the ball is 5 mm, the rotation speed of the ball milling is 300 r / min, and the ball-to-material ratio is 5.7:1;

[0053] (2) the ball-milled powder prepared in step (1) is calcined in air at a temperature of 950℃ for 6.5 h at a temperature increase rate of 8℃ / min to obtain a calcined product;

[0054] (3) the calcined product prepared in step (2) is ball milled for 4 h to obtain the large-crystal low-sodium spherical alpha-alumina powder, the ball milling uses 99 ceramic alumina balls, the rotation speed of the ball milling is 600 r / min, the ball-to-material ratio is 3.8:1, and the diameter of the ball is 5 mm.

[0055] Example 5

[0056] A microwave low-temperature calcination method for preparing a large-crystal low-sodium spherical alpha-alumina powder, comprising the following steps:

[0057] (1) mixed industrial alumina powder, composite mineralizer, and then ball-milled for 3 h at 72℃ using grinding balls to obtain a ball-milled powder, the sodium content of the industrial alumina powder being 0.48wt%, the average particle size being 90.8μm; the mass ratio of the industrial alumina powder to the composite mineralizer being 103.6:11.8; the composite mineralizer being composed of calcium dihydrogen phosphate, aluminum stearate, polyethylene oxide, fatty alcohol polyoxyethylene ether sodium sulfate, triethanolamine, barium oxide, magnesium bicarbonate, terbium oxide in a mass ratio of 4.6:1.1:2.5:0.6:1.3:0.8:0.4:0.5; the grinding balls being 99 porcelain alumina balls, the diameter of the grinding balls being 8mm, the rotation speed of the ball mill being 400r / min, and the ball-to-material ratio being 5.1:1;

[0058] (2) calcining the ball-milled powder obtained in step (1) in air at a temperature- increasing rate of 10℃ / min, a calcining temperature of 910℃, and a calcining time of 7h to obtain a calcined product;

[0059] (3) ball-milling the calcined product obtained in step (2) for 6h to obtain a large-crystal low-sodium spherical α-alumina powder, the grinding balls used being 99 porcelain alumina balls, the rotation speed of the ball mill being 500r / min, the ball-to-material ratio being 3.7:1, and the diameter of the grinding balls being 8mm.

[0060] Comparative Example 1

[0061] The microwave low-temperature calcining method for preparing a large-crystal low-sodium spherical α-alumina powder of Comparative Example 1 is basically the same as that of Example 3, except that aluminum stearate, fatty alcohol polyoxyethylene ether sodium sulfate, magnesium bicarbonate, and terbium oxide are absent from the components of the composite mineralizer.

[0062] Comparative Example 2

[0063] The microwave low-temperature calcining method for preparing a large-crystal low-sodium spherical α-alumina powder of Comparative Example 2 is basically the same as that of Comparative Example 1, except that aluminum stearate is added to the components of the composite mineralizer.

[0064] Comparative Example 3

[0065] The microwave low-temperature calcining method for preparing a large-crystal low-sodium spherical α-alumina powder of Comparative Example 3 is basically the same as that of Comparative Example 1, except that fatty alcohol polyoxyethylene ether sodium sulfate is added to the components of the composite mineralizer.

[0066] Comparative Example 4

[0067] The microwave low-temperature calcining method for preparing a large-crystal low-sodium spherical α-alumina powder of Comparative Example 4 is basically the same as that of Comparative Example 1, except that magnesium bicarbonate is added to the components of the composite mineralizer.

[0068] Comparative Example 5

[0069] The preparation method of the low-sodium large-crystal spherical α-alumina powder by microwave low-temperature calcination is basically the same as that of Comparative Example 1, except that the composition of the composite mineralizer is increased with terbium oxide.

[0070] Comparative Example 6

[0071] The preparation method of the low-sodium large-crystal spherical α-alumina powder by microwave low-temperature calcination is basically the same as that of Example 3, except that the composition of the composite mineralizer is increased with barium oxide.

[0072] Comparative Example 7

[0073] The preparation method of the low-sodium large-crystal spherical α-alumina powder by microwave low-temperature calcination is basically the same as that of Comparative Example 6, except that the composition of the composite mineralizer is increased with barium oxide.

[0074] Comparative Example 8

[0075] The preparation method of the low-sodium large-crystal spherical α-alumina powder by microwave low-temperature calcination is basically the same as that of Comparative Example 6, except that the composition of the composite mineralizer is increased with terbium oxide.

[0076] Comparative Example 9

[0077] The preparation method of the low-sodium large-crystal spherical α-alumina powder by microwave low-temperature calcination is basically the same as that of Example 3, except that the composition of the composite mineralizer is increased with calcium dihydrogen phosphate mineralizer, magnesium bicarbonate.

[0078] Comparative Example 10

[0079] The preparation method of the low-sodium large-crystal spherical α-alumina powder by microwave low-temperature calcination is basically the same as that of Comparative Example 9, except that the composition of the composite mineralizer is increased with calcium dihydrogen phosphate mineralizer.

[0080] Comparative Example 11

[0081] The preparation method of the low-sodium large-crystal spherical α-alumina powder by microwave low-temperature calcination is basically the same as that of Comparative Example 9, except that the composition of the composite mineralizer is increased with magnesium bicarbonate.

[0082] (I) Average particle size detection test of α-alumina powder

[0083] The average particle size of the α-alumina powder prepared in Examples 1-5 and Comparative Examples 1-5 was detected, and the results are shown in the following table.

[0084] Test Example Average particle diameter (μm) of α-alumina powder Example 1 26.1 Example 2 21.5 Example 3 27.2 Example 4 24.8 Example 5 29.3 Comparative Example 1 2.6 Comparative Example 2 6.4 Comparative Example 3 4.8 Comparative Example 4 10.1 Comparative Example 5 12.3

[0085] From the average particle size data of the α-alumina powder prepared from Examples 1-5 and Comparative Examples 1-5, it can be seen from the above table that the absence of aluminum stearate, fatty alcohol polyoxyethylene ether sodium sulfate, magnesium bicarbonate, and terbium oxide all affect the realization of the target of controlling the average particle size of the α-alumina powder to be >20 μm and narrow particle size distribution. This is probably because the present application utilizes the thermal effect and non-thermal effect of microwaves, cooperates aluminum stearate with fatty alcohol polyoxyethylene ether sodium sulfate, fully activates industrial alumina crystals, and promotes the growth of α-alumina primary crystals. The use of magnesium bicarbonate and terbium oxide cooperatively regulates the size of the primary crystals of the α-alumina powder, realizes the target of controlling the average particle size of the α-alumina powder to be >20 μm and narrow particle size distribution.

[0086] (ii) Sphericity test of the α-alumina powder

[0087] The sphericity of the α-alumina powder prepared from Examples 1-5 and Comparative Examples 6-8 was detected, and the results are shown in the table below.

[0088] Test Example Sphericity (%) of α-alumina powder Example 1 85.9 Example 2 88.1 Example 3 92.1 Example 4 87.4 Example 5 90.6 Comparative Example 1 70.5 Comparative Example 2 75.4 Comparative Example 3 78.7

[0089] From the sphericity of the α-alumina powder prepared from Examples 1-5, it can be seen from the above table that the target of controlling the sphericity of the obtained α-alumina powder to be >80% is achieved, reaching 85.9%-92.1%. The absence of barium oxide and terbium oxide both affect the improvement of the sphericity of the α-alumina powder. It can be calculated from the data in the above table that barium oxide and terbium oxide have a synergistic effect on improving the sphericity. This is probably because the present application uses barium oxide and terbium oxide to cooperatively accelerate the growth of α-alumina single crystals, and at the same time, improve the sphericity of the α-alumina powder, realizing the synergistic improvement of the sphericity.

[0090] (iii) Na2O content test of the α-alumina powder

[0091] The Na2O content of the α-alumina powder prepared from Examples 1-5 and Comparative Examples 9-11 was detected, and the results are shown in the table below.

[0092]

[0093] From the Na2O content data of the α-alumina powder prepared from Examples 1-5 and Comparative Examples 9-11, it can be seen from the above table that the absence of calcium dihydrogen phosphate mineralizer and magnesium bicarbonate both affect the reduction of the sodium content of the α-alumina powder. This is probably because the present application uses calcium dihydrogen phosphate and magnesium bicarbonate mineralizers to cooperatively remove sodium impurities, thereby obtaining low-sodium α-alumina powder and realizing the target of Na2O <0.02 wt%.

[0094] (iv) Purity test of the α-alumina powder

[0095] The purity of the α-alumina powder prepared in Examples 1-5 was tested, and the results are shown in the following table.

[0096] Test Example Purity (%) of α-alumina powder Example 1 99.2 Example 2 99.1 Example 3 99.5 Example 4 99.3 Example 5 99.4

[0097] As shown in the above table, the purity of the α-alumina powder prepared in Examples 1-5 is >99%, and can be widely used in the fields of heat-conducting plastic, high-heat-conducting gel, high-heat-conducting gasket, electronic packaging, etc.

[0098] The above description of disclosed examples enables one skilled in the art to make or use the application. Numerous modifications to these examples will be apparent to those skilled in the art, and the general principles defined herein can be applied to other examples without departing from the spirit or scope of the application. Therefore, the present application is not intended to be limited to the examples shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing large-scale, low-sodium spherical α-alumina powder by microwave low-temperature calcination, characterized in that, Includes the following steps: (1) After mixing industrial alumina powder and composite mineralizer, the mixture is ball-milled at a temperature of 62-73℃ for 3-5 hours to obtain ball-milled powder. The mass ratio of industrial alumina powder to composite mineralizer is (92.4-105.3):(8.6-12.2). The sodium content of the industrial alumina powder is 0.35-0.5wt%, and the average particle size is 50.3-100.6μm. The composite mineralizer is composed of calcium dihydrogen phosphate, aluminum stearate, polyethylene oxide, sodium fatty alcohol polyoxyethylene ether sulfate, triethanolamine, barium oxide, magnesium bicarbonate, and terbium oxide in a mass ratio of (3.1-5.4):(0.6-1.1):(2.3-2.8):(0.3-0.7):(1-1.5):(0.4-0.8):(0.2-0.4):(0.3-0.5). (2) The ball milled powder obtained in step (1) is subjected to microwave calcination. The heating rate is controlled at 6-10℃ / min, and the calcination temperature is 850-980℃ for 5-10h to obtain the calcined product. (3) The calcined material obtained in step (2) is ball-milled for 3-6 hours to obtain large-scale low-sodium spherical α-alumina powder, wherein the Na2O content in the large-scale low-sodium spherical α-alumina powder is less than 0.02 wt%.

2. The microwave low-temperature calcination preparation method for large-scale low-sodium spherical α-alumina powder according to claim 1, characterized in that, The grinding ball mentioned in step (1) or step (3) is a 99% ceramic alumina ball with a diameter of 4-8 mm.

3. The microwave low-temperature calcination preparation method for large-scale low-sodium spherical α-alumina powder according to claim 1, characterized in that, In step (1), the ball mill rotation speed is 300-400 r / min.

4. The microwave low-temperature calcination preparation method for large-scale low-sodium spherical α-alumina powder according to claim 1, characterized in that, In step (1), the ball-to-material ratio is 5-6:

1.

5. The microwave low-temperature calcination preparation method for large-scale low-sodium spherical α-alumina powder according to claim 1, characterized in that, In step (3), the ball mill rotation speed is 500-600 r / min.

6. The microwave low-temperature calcination preparation method for large-scale low-sodium spherical α-alumina powder according to claim 1, characterized in that, In step (3), the ball-to-material ratio is 3.3-4:1.

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