Shaft structure and aluminum nitride heater

Abstract

The invention discloses a shaft structure and an aluminum nitride heater, and belongs to the technical field of aluminum nitride heaters, the shaft structure comprises an aluminum nitride ceramic section, an aluminum nitride and aluminum oxide transition section and an aluminum oxide ceramic section, and the aluminum nitride ceramic section, the aluminum nitride and aluminum oxide transition section and the aluminum oxide ceramic section are sequentially connected from top to bottom; the aluminum nitride heater comprises an aluminum nitride heating plate; and the aluminum nitride heating plate is connected with the aluminum nitride ceramic section. According to the technical scheme, it can be guaranteed that the materials at the joint of the shaft structure and the aluminum nitride heating disc are the same or similar, the thermal expansion coefficients of the materials are basically consistent, the materials can be transited to aluminum oxide through the transition layer, the heat conductivity coefficient of the aluminum oxide is lower than that of aluminum nitride, and therefore loss of heat on the aluminum nitride heating disc through the shaft structure is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum nitride heaters, and in particular to a shaft structure and an aluminum nitride heater. Background Art

[0002] Aluminum nitride heaters are composed of a ceramic disk and a ceramic shaft, both of which are made of aluminum nitride. Aluminum nitride heaters are used in high temperature conditions, and require the ceramic disk to have a high temperature uniformity when in use. However, due to the heat dissipation of the aluminum nitride shaft, the temperature of the ceramic disk at the shaft position during the use of the heater deviates from that at other positions. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a shaft structure and an aluminum nitride heater to solve the problems raised in the background technology, optimize the ceramic shaft structure, and improve the temperature uniformity of the aluminum nitride heater.

[0004] In order to solve the above technical problems, the technical solution of the present invention is:

[0005] On one hand, the present invention discloses a shaft structure, which includes an aluminum nitride ceramic section, an aluminum nitride and aluminum oxide transition section, and an aluminum oxide ceramic section. The aluminum nitride ceramic section, the aluminum nitride and aluminum oxide transition section, and the aluminum oxide ceramic section are sequentially connected from top to bottom.

[0006] Preferably, the length of the aluminum nitride ceramic section is equal to the aluminum nitride and aluminum oxide transition section, and the length of the aluminum nitride and aluminum oxide transition section is less than the length of the aluminum oxide ceramic section.

[0007] Preferably, the length of the aluminum nitride ceramic segment is 3 / 10 of the total length of the shaft structure, the length of the aluminum nitride and alumina transition segment is 3 / 10 of the total length of the shaft structure, and the length of the alumina ceramic segment is 4 / 10 of the total length of the shaft structure.

[0008] Preferably, the aluminum nitride ceramic segment includes a first aluminum nitride segment, a second aluminum nitride segment and a third aluminum nitride segment, the first aluminum nitride segment, the second aluminum nitride segment and the third aluminum nitride segment are connected in sequence, the lengths of the first aluminum nitride segment, the second aluminum nitride segment and the third aluminum nitride segment are all 1 / 10 of the total length of the shaft structure, the first aluminum nitride segment includes, by mass percentage, 90-100% aluminum nitride and 0-10% aluminum oxide, the second aluminum nitride segment includes, by mass percentage, 80-90% aluminum nitride and 10-20% aluminum oxide, and the third aluminum nitride segment includes, by mass percentage, 70-80% aluminum nitride and 20-30% aluminum oxide.

[0009] Preferably, the aluminum nitride and aluminum oxide transition section includes a first transition section, a second transition section, and a third transition section. The first transition section, the second transition section, and the third transition section are connected in sequence. The lengths of the first transition section, the second transition section, and the third transition section are all 1 / 10 of the total length of the shaft structure. The first transition section includes 60-70% aluminum nitride and 30-40% aluminum oxide by mass percentage, the second transition section includes 50-60% aluminum nitride and 40-50% aluminum oxide by mass percentage, and the third transition section includes 40-50% aluminum nitride and 50-60% aluminum oxide by mass percentage.

[0010] Preferably, the alumina ceramic segment includes a first alumina segment, a second alumina segment, a third alumina segment and a fourth alumina segment, the first alumina segment, the second alumina segment, the third alumina segment and the fourth alumina segment are connected in sequence, the lengths of the first alumina segment, the second alumina segment, the third alumina segment and the fourth alumina segment are all 1 / 10 of the total length of the shaft structure, the first alumina segment includes, by mass percentage, 30-40% aluminum nitride and 60-70% alumina, the second alumina segment includes, by mass percentage, 20-30% aluminum nitride and 70-80% alumina, the third alumina segment includes, by mass percentage, 10-20% aluminum nitride and 80-90% alumina, and the fourth alumina segment includes, by mass percentage, 0-10% aluminum nitride and 90-100% alumina.

[0011] Preferably, the third aluminum nitride segment is connected to the first transition segment, and the third transition segment is connected to the first aluminum oxide segment.

[0012] Preferably, the shaft structure is prepared by isostatic pressing and then sintering ceramic granulated powder.

[0013] Another aspect of the present invention discloses an aluminum nitride heater including the shaft structure, wherein the aluminum nitride heater includes an aluminum nitride heating disk, and the aluminum nitride heating disk is connected to the aluminum nitride ceramic segment.

[0014] The above technical solution has the following beneficial effects:

[0015] In the technical solution of the present application, since the aluminum nitride ceramic section is connected to the aluminum nitride heating plate, it can be ensured that the shaft structure and the aluminum nitride heating plate are made of the same or similar materials at the joint, so that their thermal expansion coefficients are basically consistent, and then transition to aluminum oxide through the aluminum nitride and aluminum oxide transition section. Aluminum oxide has a lower thermal conductivity than aluminum nitride, thereby reducing the heat loss on the aluminum nitride heating plate through the shaft structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1It is a schematic structural diagram of the aluminum nitride heater of the present invention. DETAILED DESCRIPTION

[0017] The specific embodiments of the present invention are further described below in conjunction with the accompanying drawings. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0018] Example 1

[0019] refer to Figure 1 A shaft structure includes an aluminum nitride ceramic section, an aluminum nitride and aluminum oxide transition section, and an aluminum oxide ceramic section, wherein the aluminum nitride ceramic section, the aluminum nitride and aluminum oxide transition section, and the aluminum oxide ceramic section are sequentially connected from top to bottom;

[0020] The aluminum nitride heater includes the above-mentioned shaft structure and the aluminum nitride heating disk 11, and the shaft structure is connected to the aluminum nitride heating disk 11. Due to the high thermal conductivity of aluminum nitride material, the heat of the aluminum nitride heater at the shaft structure will be dissipated with the shaft structure. In order to reduce the influence of the shaft structure on the heat of the aluminum nitride heating disk 11, the shaft structure is designed as a gradient material structure in the present application, that is, the closer the shaft structure is to one end of the aluminum nitride heating disk 11, the material is aluminum nitride or mainly aluminum nitride, and the aluminum nitride content in the material at the position where the shaft structure is far away from the aluminum nitride heating disk 11 decreases with the increase of distance. At the position farthest from the aluminum nitride heating disk 11, its material is aluminum oxide or mainly aluminum oxide. The aluminum oxide material has a lower thermal conductivity than the aluminum nitride material, thereby reducing the heat dissipated from the aluminum nitride heating disk 11 through the shaft structure. The design of the shaft structure can not only ensure the consistency of the thermal expansion coefficient of the shaft structure and the aluminum nitride heating disk 11 at the junction, but also reduce the heat dissipation of the shaft structure, thereby optimizing the shaft structure and improving the temperature uniformity of the aluminum nitride heater.

[0021] The length of the aluminum nitride ceramic section is equal to the aluminum nitride and aluminum oxide transition section, and the length of the aluminum nitride and aluminum oxide transition section is less than the length of the aluminum oxide ceramic section. The aluminum nitride ceramic section is mainly made of aluminum nitride, which is one end connected to the aluminum nitride heating plate 11, and the closer to the aluminum nitride heating plate 11, the higher the content of aluminum nitride material, so as to ensure the consistency of the thermal expansion coefficient of the aluminum nitride heating plate 11 at the joint;

[0022] The length of the aluminum nitride ceramic section is 3 / 10 of the total length of the shaft structure, the length of the aluminum nitride and aluminum oxide transition section is 3 / 10 of the total length of the shaft structure, and the length of the aluminum oxide ceramic section is 4 / 10 of the total length of the shaft structure;

[0023] The aluminum nitride ceramic segment includes a first aluminum nitride segment 1, a second aluminum nitride segment 2 and a third aluminum nitride segment 3, which are connected in sequence, and the lengths of the first aluminum nitride segment 1, the second aluminum nitride segment 2 and the third aluminum nitride segment 3 are all 1 / 10 of the total length of the shaft structure. The first aluminum nitride segment 1 includes 90-100% aluminum nitride and 0-10% aluminum oxide by mass percentage, the second aluminum nitride segment 2 includes 80-90% aluminum nitride and 10-20% aluminum oxide by mass percentage, and the third aluminum nitride segment 3 includes 70-80% aluminum nitride and 20-30% aluminum oxide by mass percentage;

[0024] The main component of the first aluminum nitride segment 1 is aluminum nitride, which is one end connected to the aluminum nitride heating plate 11, and can maintain the same thermal expansion coefficient as the aluminum nitride heating plate 11. The first aluminum nitride segment 1, the second aluminum nitride segment 2, and the third aluminum nitride segment 3 are made of ceramic granulated powder after isostatic pressing and sintering, forming aluminum nitride ceramic segments in which the aluminum nitride content in the first aluminum nitride segment 1, the second aluminum nitride segment 2, and the third aluminum nitride segment 3 decreases successively, but the main component of this segment is aluminum nitride, such as the first aluminum nitride segment 1 includes 90-100% aluminum nitride, and the rest is aluminum oxide, preferably 95% aluminum nitride and 5% aluminum oxide, the second aluminum nitride segment 2 includes: 80-90% aluminum nitride and 10-20% aluminum oxide, preferably 85% aluminum nitride, and 15% aluminum oxide, the third aluminum nitride segment 3 includes 70-80% aluminum nitride and 20-30% aluminum oxide, preferably 75% aluminum nitride and 25% aluminum oxide;

[0025] The aluminum nitride and aluminum oxide transition section includes a first transition section 4, a second transition section 5, and a third transition section 6, which are connected in sequence. The lengths of the first transition section 4, the second transition section 5, and the third transition section 6 are all 1 / 10 of the total length of the shaft structure. The first transition section 4 includes 60-70% aluminum nitride and 30-40% aluminum oxide by mass percentage, the second transition section 5 includes 50-60% aluminum nitride and 40-50% aluminum oxide by mass percentage, and the third transition section 6 includes 40-50% aluminum nitride and 50-60% aluminum oxide by mass percentage;

[0026] The first transition section 4 comprises, by mass percentage, 60-70% aluminum nitride and 30-40% aluminum oxide, preferably 65% ​​aluminum nitride and 35% aluminum oxide, the second transition section 5 comprises, by mass percentage, 50-60% aluminum nitride and 40-50% aluminum oxide, preferably 55% aluminum nitride and 45% aluminum oxide, the third transition section 6 comprises, by mass percentage, 40-50% aluminum nitride and 50-60% aluminum oxide, preferably 45% aluminum nitride and 55% aluminum oxide, the first transition section 4 is connected to the third aluminum nitride section 3 by ceramic sintering method;

[0027] The alumina ceramic segment includes a first alumina segment 7, a second alumina segment 8, a third alumina segment 9 and a fourth alumina segment 10, which are connected in sequence. The lengths of the first alumina segment 7, the second alumina segment 8, the third alumina segment 9 and the fourth alumina segment 10 are all 1 / 10 of the total length of the shaft structure. The first alumina segment 7 includes, by mass percentage, 30-40% aluminum nitride and 60-70% alumina, preferably 35% aluminum nitride. and 65 aluminum oxide, the second aluminum oxide segment 8 comprises by mass percentage: 20-30% aluminum nitride and 70-80% aluminum oxide, preferably 25% aluminum nitride and 75% aluminum oxide, the third aluminum oxide segment 9 comprises by mass percentage: 10-20% aluminum nitride and 80-90% aluminum oxide, preferably 15% aluminum nitride and 85% aluminum oxide, the fourth aluminum oxide segment 10 comprises by mass percentage: 0-10% aluminum nitride and 90-100% aluminum oxide, preferably 5% aluminum nitride and 95% aluminum oxide;

[0028] For the alumina ceramic segment, the main material is alumina, and the remaining part is aluminum nitride. The first alumina segment 7, the second alumina segment 8, the third alumina segment 9 and the fourth alumina segment 10 are pressed and sintered together to form an alumina ceramic segment, wherein one end of the first alumina segment 7 is connected to the third transition segment 6 of the aluminum nitride and alumina transition segments, and they are also connected together by sintering. Each segment is prepared separately first, and then sintered together to form a shaft structure;

[0029] The third aluminum nitride section 3 is connected to the first transition section 4, and the third transition section 6 is connected to the first aluminum oxide section 7;

[0030] First, a first aluminum nitride segment 1, a second aluminum nitride segment 2, a third aluminum nitride segment 3, a first transition segment 4, a second transition segment 5, a third transition segment 6, a first aluminum oxide segment 7, a second aluminum oxide segment 8, a third aluminum oxide segment 9, and a fourth aluminum oxide segment 10 are prepared by using ceramic granulated powder, and then sintered after isostatic pressing to prepare a shaft structure;

[0031] In the technical solution of the present application, since the aluminum nitride ceramic segment is connected to the aluminum nitride heating plate 11, it can be ensured that the shaft structure and the aluminum nitride heating plate 11 are made of the same or similar materials at the joint, so that their thermal expansion coefficients are basically consistent, and then transition to aluminum oxide through the aluminum nitride and aluminum oxide transition segment, and utilize the lower thermal conductivity of aluminum oxide than that of aluminum nitride, thereby reducing the heat loss on the aluminum nitride heating plate 11 through the shaft structure.

[0032] Example 2

[0033] A shaft structure includes an aluminum nitride ceramic section, an aluminum nitride and aluminum oxide transition section, and an aluminum oxide ceramic section, wherein the aluminum nitride ceramic section, the aluminum nitride and aluminum oxide transition section, and the aluminum oxide ceramic section are sequentially connected from top to bottom;

[0034] The length of the aluminum nitride ceramic section is equal to the aluminum nitride and aluminum oxide transition section, and the length of the aluminum nitride and aluminum oxide transition section is shorter than the length of the aluminum oxide ceramic section;

[0035] The length of the aluminum nitride ceramic section is 3 / 10 of the total length of the shaft structure, the length of the aluminum nitride and aluminum oxide transition section is 3 / 10 of the total length of the shaft structure, and the length of the aluminum oxide ceramic section is 4 / 10 of the total length of the shaft structure;

[0036] The aluminum nitride ceramic segment includes a first aluminum nitride segment 1, a second aluminum nitride segment 2 and a third aluminum nitride segment 3, which are connected in sequence, and the lengths of the first aluminum nitride segment 1, the second aluminum nitride segment 2 and the third aluminum nitride segment 3 are all 1 / 10 of the total length of the shaft structure. The first aluminum nitride segment 1 includes 100% aluminum nitride by mass percentage, the second aluminum nitride segment 2 includes 90% aluminum nitride and 10% aluminum oxide by mass percentage, and the third aluminum nitride segment 3 includes 80% aluminum nitride and 20% aluminum oxide by mass percentage;

[0037] The aluminum nitride and aluminum oxide transition section includes a first transition section 4, a second transition section 5, and a third transition section 6, which are connected in sequence. The lengths of the first transition section 4, the second transition section 5, and the third transition section 6 are all 1 / 10 of the total length of the shaft structure. The first transition section 4 includes 70% aluminum nitride and 30% aluminum oxide by mass percentage, the second transition section 5 includes 60% aluminum nitride and 40% aluminum oxide by mass percentage, and the third transition section 6 includes 50% aluminum nitride and 50% aluminum oxide by mass percentage;

[0038] The alumina ceramic segment includes a first alumina segment 7, a second alumina segment 8, a third alumina segment 9 and a fourth alumina segment 10, which are connected in sequence. The lengths of the first alumina segment 7, the second alumina segment 8, the third alumina segment 9 and the fourth alumina segment 10 are all 1 / 10 of the total length of the shaft structure. The first alumina segment 7 includes 40% aluminum nitride and 60% aluminum oxide by mass percentage, the second alumina segment 8 includes 30% aluminum nitride and 70% aluminum oxide by mass percentage, the third alumina segment 9 includes 20% aluminum nitride and 80% aluminum oxide by mass percentage, and the fourth alumina segment 10 includes 10% aluminum nitride and 90% aluminum oxide by mass percentage;

[0039] The third aluminum nitride section 3 is connected to the first transition section 4, and the third transition section 6 is connected to the first aluminum oxide section 7;

[0040] First, a first aluminum nitride segment 1, a second aluminum nitride segment 2, a third aluminum nitride segment 3, a first transition segment 4, a second transition segment 5, a third transition segment 6, a first alumina segment 7, a second alumina segment 8, a third alumina segment 9, and a fourth alumina segment 10 are prepared by ceramic granulation powder, and then sintered after isostatic pressing to prepare an axis structure.

[0041] Example 3

[0042] A shaft structure includes an aluminum nitride ceramic section, an aluminum nitride and aluminum oxide transition section, and an aluminum oxide ceramic section, wherein the aluminum nitride ceramic section, the aluminum nitride and aluminum oxide transition section, and the aluminum oxide ceramic section are sequentially connected from top to bottom;

[0043] The length of the aluminum nitride ceramic section is equal to the aluminum nitride and aluminum oxide transition section, and the length of the aluminum nitride and aluminum oxide transition section is shorter than the length of the aluminum oxide ceramic section;

[0044] The length of the aluminum nitride ceramic section is 3 / 10 of the total length of the shaft structure, the length of the aluminum nitride and aluminum oxide transition section is 3 / 10 of the total length of the shaft structure, and the length of the aluminum oxide ceramic section is 4 / 10 of the total length of the shaft structure;

[0045] The aluminum nitride ceramic segment includes a first aluminum nitride segment 1, a second aluminum nitride segment 2 and a third aluminum nitride segment 3, which are connected in sequence, and the lengths of the first aluminum nitride segment 1, the second aluminum nitride segment 2 and the third aluminum nitride segment 3 are all 1 / 10 of the total length of the shaft structure. The first aluminum nitride segment 1 includes 90% aluminum nitride and 10% aluminum oxide by mass percentage, the second aluminum nitride segment 2 includes 80% aluminum nitride and 20% aluminum oxide by mass percentage, and the third aluminum nitride segment 3 includes 70% aluminum nitride and 30% aluminum oxide by mass percentage;

[0046] The aluminum nitride and aluminum oxide transition section includes a first transition section 4, a second transition section 5, and a third transition section 6, which are connected in sequence. The lengths of the first transition section 4, the second transition section 5, and the third transition section 6 are all 1 / 10 of the total length of the shaft structure. The first transition section 4 includes 60% aluminum nitride and 40% aluminum oxide by mass percentage, the second transition section 5 includes 50% aluminum nitride and 50% aluminum oxide by mass percentage, and the third transition section 6 includes 40% aluminum nitride and 60% aluminum oxide by mass percentage;

[0047] The alumina ceramic segment includes a first alumina segment 7, a second alumina segment 8, a third alumina segment 9 and a fourth alumina segment 10, which are connected in sequence. The lengths of the first alumina segment 7, the second alumina segment 8, the third alumina segment 9 and the fourth alumina segment 10 are all 1 / 10 of the total length of the shaft structure. The first alumina segment 7 includes 30% aluminum nitride and 70% aluminum oxide by mass percentage, the second alumina segment 8 includes 20% aluminum nitride and 80% aluminum oxide by mass percentage, the third alumina segment 9 includes 10% aluminum nitride and 90% aluminum oxide by mass percentage, and the fourth alumina segment 10 includes 100% aluminum oxide by mass percentage;

[0048] The third aluminum nitride section 3 is connected to the first transition section 4, and the third transition section 6 is connected to the first aluminum oxide section 7;

[0049] First, a first aluminum nitride segment 1, a second aluminum nitride segment 2, a third aluminum nitride segment 3, a first transition segment 4, a second transition segment 5, a third transition segment 6, a first alumina segment 7, a second alumina segment 8, a third alumina segment 9, and a fourth alumina segment 10 are prepared by ceramic granulation powder, and then sintered after isostatic pressing to prepare an axis structure.

[0050] Example 4

[0051] An aluminum nitride heater including the above-mentioned shaft structure, the aluminum nitride heater including an aluminum nitride heating disk 11, the aluminum nitride heating disk 11 is connected to the aluminum nitride ceramic segment, specifically, the first aluminum nitride containing the most aluminum nitride in the aluminum nitride segment on the shaft structure is connected to the aluminum nitride heating disk 11;

[0052] Not only can it ensure that the shaft structure and the aluminum nitride heating plate 11 are made of the same material or have the same main components at the joint, so that their thermal expansion coefficients are consistent, but it can also transition to an alumina ceramic section whose main component is alumina, and utilize the lower thermal conductivity of alumina than aluminum nitride, thereby reducing the heat loss on the aluminum nitride heating plate 11 through the shaft structure.

[0053] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments are made without departing from the principles and spirit of the present invention, and still fall within the scope of protection of the present invention.

Claims

1. A shaft structure, characterized in that: The shaft structure comprises an aluminum nitride ceramic section, an aluminum nitride and aluminum oxide transition section, and an aluminum oxide ceramic section. The aluminum nitride ceramic section, the aluminum nitride and aluminum oxide transition section, and the aluminum oxide ceramic section are sequentially connected and arranged from top to bottom.

2. A shaft structure according to claim 1, characterized in that: The length of the aluminum nitride ceramic section is equal to that of the aluminum nitride and aluminum oxide transition section, and the length of the aluminum nitride and aluminum oxide transition section is less than that of the aluminum oxide ceramic section.

3. A shaft structure according to claim 2, characterized in that: The length of the aluminum nitride ceramic section is 3 / 10 of the total length of the shaft structure, the length of the aluminum nitride and aluminum oxide transition section is 3 / 10 of the total length of the shaft structure, and the length of the aluminum oxide ceramic section is 4 / 10 of the total length of the shaft structure.

4. The shaft structure according to claim 1, characterized in that: The aluminum nitride ceramic segment includes a first aluminum nitride segment, a second aluminum nitride segment and a third aluminum nitride segment. The first aluminum nitride segment, the second aluminum nitride segment and the third aluminum nitride segment are connected in sequence. The lengths of the first aluminum nitride segment, the second aluminum nitride segment and the third aluminum nitride segment are all 1 / 10 of the total length of the shaft structure. The first aluminum nitride segment includes 90-100% aluminum nitride and 0-10% aluminum oxide by mass percentage, the second aluminum nitride segment includes 80-90% aluminum nitride and 10-20% aluminum oxide by mass percentage, and the third aluminum nitride segment includes 70-80% aluminum nitride and 20-30% aluminum oxide by mass percentage.

5. A shaft structure according to claim 4, characterized in that: The aluminum nitride and aluminum oxide transition section includes a first transition section, a second transition section, and a third transition section. The first transition section, the second transition section, and the third transition section are connected in sequence. The lengths of the first transition section, the second transition section, and the third transition section are all 1 / 10 of the total length of the shaft structure. The first transition section includes 60-70% aluminum nitride and 30-40% aluminum oxide by mass percentage, the second transition section includes 50-60% aluminum nitride and 40-50% aluminum oxide by mass percentage, and the third transition section includes 40-50% aluminum nitride and 50-60% aluminum oxide by mass percentage.

6. A shaft structure according to claim 5, characterized in that: The alumina ceramic segment includes a first alumina segment, a second alumina segment, a third alumina segment and a fourth alumina segment. The first alumina segment, the second alumina segment, the third alumina segment and the fourth alumina segment are connected in sequence. The lengths of the first alumina segment, the second alumina segment, the third alumina segment and the fourth alumina segment are all 1 / 10 of the total length of the shaft structure. The first alumina segment includes 30-40% aluminum nitride and 60-70% alumina by mass percentage, the second alumina segment includes 20-30% aluminum nitride and 70-80% alumina by mass percentage, the third alumina segment includes 10-20% aluminum nitride and 80-90% alumina by mass percentage, and the fourth alumina segment includes 0-10% aluminum nitride and 90-100% alumina by mass percentage.

7. A shaft structure according to claim 6, characterized in that: The third aluminum nitride segment is connected to the first transition segment, and the third transition segment is connected to the first aluminum oxide segment.

8. The shaft structure according to claim 6, characterized in that: The shaft structure is prepared by isostatic pressing and then sintering ceramic granulated powder.

9. An aluminum nitride heater comprising the shaft structure as claimed in any one of claims 1 to 8, characterized in that: The aluminum nitride heater comprises an aluminum nitride heating disk, and the aluminum nitride heating disk is connected to the aluminum nitride ceramic segment.

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