Black aluminum oxide ceramic with adjustable resistivity and preparation method thereof

Abstract

The invention relates to black aluminum oxide ceramic with adjustable resistivity and a preparation method thereof. The preparation method of the black aluminum oxide ceramic with the adjustable resistivity comprises the following steps: (1) mixing MnO2 powder, Fe2O3 powder, NiO powder, CoO powder and Cr2O3 powder, and calcining to obtain a black pigment; and (2) mixing Al2O3 powder with the black pigment and the resistivity regulator to obtain black aluminum oxide raw material powder, and then carrying out molding, glue discharging and sintering to obtain the black aluminum oxide ceramic with the adjustable resistivity.

Description

Technical Field

[0001] This invention belongs to the field of functional ceramic material preparation technology, specifically relating to a black alumina ceramic with adjustable resistivity and its preparation method. Background Technology

[0002] Advanced large-scale integrated circuit manufacturing involves hundreds of process steps, requiring wafers to be transferred and processed / tested between hundreds of different pieces of equipment. During processing, the wafers must be held very stably on the equipment. Electrostatic chucks use a high-voltage electric field to induce polarized charges on the wafer surface, creating electrostatic forces that firmly hold it in place. However, in semiconductor processing, the accumulation of static electricity caused by wafer friction can lead to safety hazards; therefore, it is necessary to control the chuck's volume resistivity (10⁻⁶ Ω·cm). 7 ~10 11 (Ω·cm), thereby eliminating or reducing the accumulation of static electricity.

[0003] Furthermore, to prevent light reflected from the chuck during high-precision processing such as photolithography from affecting the reliability of internal photosensitive elements, electrostatic chucks often need to have high light absorption. Given these requirements, black alumina ceramic stands out due to its excellent light absorption capabilities, making it the best choice for handling such sensitive components. However, current black alumina often suffers from uneven coloring and high volume resistivity, failing to meet the demands of industrial applications. Summary of the Invention

[0004] To address the problems of uneven coloring and high volume resistivity in existing black ceramic technologies, this invention provides a black alumina ceramic with adjustable resistivity and its preparation method. This method is simple, produces black ceramics with high absorbance and a stable, uniform black color, and allows for independent adjustment of the volume resistivity according to actual needs, resulting in a high yield.

[0005] In a first aspect, the present invention provides a method for preparing a black alumina ceramic with adjustable resistivity, the method comprising the following steps: (1) MnO2, Fe2O3, NiO, CoO and Cr2O3 powders were mixed and calcined to obtain a black pigment; (2) The Al2O3 powder is mixed with the black pigment and resistivity regulator to obtain black alumina raw material powder, and then the powder is shaped, debinded and sintered to obtain the black alumina ceramic with adjustable resistivity.

[0006] Preferably, in step (1), based on a total mass percentage of 100%, the mass percentage of MnO2 is 55-70%, the mass percentage of Fe2O3 is 10-25%, the mass percentage of NiO is 6-10%, the mass percentage of CoO is 4-8%, and the mass percentage of Cr2O3 is 2-6%.

[0007] Preferably, in step (1), the mixing method is ball milling; wherein, in the ball milling process, the mass ratio of raw material to ball mill is 1:3.5, the ball milling time is 20-30h, the rotation speed is 200-250r / min, and the solvent is anhydrous ethanol; preferably, the slurry after ball milling is dried and sieved, the drying temperature is 50-60℃, the drying time is 36-48h, and the sieve mesh size is 80-100.

[0008] Preferably, in step (1), the heating rate of calcination is 2-5℃ / min, the calcination temperature is 1000-1200℃, the holding time is 2-5h, and the calcination atmosphere is air, vacuum, or nitrogen.

[0009] Preferably, in step (2), the particle size of the Al2O3 powder is 400-600 nm, and the resistivity regulator includes at least one of TiO2, SnO2, ZnO, In2O3, and Ga2O3.

[0010] Preferably, in step (2), with the total mass of Al2O3 powder, the black pigment, and the resistivity regulator being 100%, the mass percentage of Al2O3 is 70-98%, the mass percentage of the black pigment is 0-20%, and the mass percentage of the resistivity regulator is 0-20%.

[0011] Preferably, in step (2), the mixing method is ball milling; wherein, in the ball milling process, the mass ratio of raw material to ball mill is 1:3.5, the ball milling time is 20-30h, the rotation speed is 200-250r / min, and the solvent is anhydrous ethanol; preferably, the slurry after ball milling is dried and sieved, the drying temperature is 50-60℃, the drying time is 36-48h, and the sieve mesh size is 80-100.

[0012] Preferably, in step (2), the molding method includes dry pressing and cold isostatic pressing; preferably, the pressure of cold isostatic pressing is 100-200 MPa; The temperature for discharging the adhesive is 600-800℃, the heating rate is 1-2℃ / min, the holding time is 2-5h, and the atmosphere for discharging the adhesive is air, vacuum, or nitrogen.

[0013] Preferably, in step (2), the sintering process includes: raising the temperature to 800-1000℃ at 3-5℃ / min and holding for 2-3 hours, then raising the temperature to 1500-1600℃ at 1-2℃ / min and holding for 3-5 hours, then lowering the temperature to 800-1000℃ at 1-2℃ / min, then lowering the temperature to 500-600℃ at 3-5℃ / min, and finally lowering to room temperature; preferably, the sintering atmosphere includes air, vacuum or nitrogen.

[0014] Secondly, the present invention provides a black alumina ceramic with adjustable resistivity obtained according to the above preparation method.

[0015] Beneficial effects (1) This invention uses black pigment as a colorant and TiO2, SnO2, ZnO, In2O3, and Ga2O3 as resistivity modifiers to prepare black ceramics with an absorbance of 95% and uniform coloring, and a volume resistivity of less than 10. 5 ~10 12 Adjustable within the range of Ω·cm, the generated static charge can be discharged in a timely manner within this range, giving the electrostatic chuck an anti-static function and preventing damage to electronic components due to the accumulation of static electricity during the production and use of electronic components. (2) The samples prepared by this invention can be processed according to requirements to meet the needs of practical applications. Attached Figure Description

[0016] Figure 1 This is a photograph of the polished surface of the black alumina ceramic prepared in Example 1; Figure 2 The graph shows a comparison of the reflectance of the alumina ceramic materials prepared in Examples 1-7. Detailed Implementation

[0017] The present invention will be further illustrated by the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention.

[0018] The following is an exemplary description of a method for preparing the resistivity-tunable black alumina ceramic provided by the present invention. The preparation method may include the following steps: (1) MnO2, Fe2O3, NiO, CoO and Cr2O3 powders were mixed and calcined to obtain a black pigment; (2) The Al2O3 powder is mixed with the black pigment and resistivity regulator to obtain black alumina raw material powder, and then the powder is shaped, debinded and sintered to obtain the black alumina ceramic with adjustable resistivity.

[0019] In some implementations, in step (1), based on a total mass percentage of 100%, the mass percentage of MnO2 can be 55-70%, the mass percentage of Fe2O3 can be 10-25%, the mass percentage of NiO can be 6-10%, the mass percentage of CoO can be 4-8%, and the mass percentage of Cr2O3 can be 2-6%.

[0020] Among them, Mn in MnO2 4+ High temperature reduction to Mn 2+ / Mn 3+ It preferentially enters the Al-O octahedron and produces broadband absorption in the visible light range of 400-700 nm. However, excessive MnO2 can induce micropores due to partial vaporization at high temperatures, resulting in lower mechanical properties. Therefore, it needs to be controlled at 55-70 wt% (as a percentage of total colorant). Fe 3+ / Fe 2+ The 3d electrons of Mn have a strong absorption band near 580 nm, which can interact with Mn 2+ Co 2+ The superposition of absorption bands from plasma forms a continuous absorption spectrum covering 400-700 nm, thereby increasing visible light absorbance. However, excessive Fe₂O₃ can lead to Fe... 3+ Enrichment, supersaturation, and recrystallization produce coherent red scattering, macroscopically canceling out the blackness and resulting in a brownish-red hue. Therefore, the Fe2O3 content should be controlled at (10-25%, accounting for the total colorant); NiO in NiO 2+ It exhibits characteristic dd absorption at 650-680 nm, which can eliminate the residual brownish-red hue of the Mn-Fe system, thus presenting a purer black color. Excessive NiO increases liquid phase viscosity and hinders the expulsion of pores during sintering; therefore, the addition amount is generally 6-10% (accounting for the total colorant). CoO contains Co... 2+ It forms a mixed spinel (Mn,Fe,Co)3O4 with Mn and Fe, which stabilizes the high-temperature color and reduces the "reddish" phenomenon after firing. In addition, Co 2+ The transition produces strong absorption at 600-700 nm, and an appropriate amount (4-8%, accounting for 4% of the total colorant) can deepen the blackness; Cr in Cr2O3 3+ With Al 3+ With similar radii, it preferentially dissolves in the Al2O3 lattice, producing absorption at 550-650 nm. At the same time, it inhibits the desolvation of Mn and Fe, maintaining color stability. However, excessive amounts can easily generate independent Cr2O3 phases, increasing hardness and hindering subsequent processing. Therefore, an appropriate amount (2-6%, accounting for the total colorant) is sufficient.

[0021] In some embodiments, in step (1), the mixing method can be ball milling; wherein, in the ball milling process, the mass ratio of raw material to ball mill can be 1:3.5, the ball milling time can be 20-30h, the rotation speed can be 200-250r / min, and the solvent can be anhydrous ethanol; preferably, the slurry after ball milling is dried and sieved, the drying temperature can be 50-60℃, the drying time can be 36-48h, and the sieve mesh size can be 80-100.

[0022] In some embodiments, in step (1), the heating rate of calcination can be 2-5℃ / min, the calcination temperature can be 1000-1200℃, the holding time can be 2-5h, and the calcination atmosphere can be air, vacuum, or nitrogen.

[0023] In some embodiments, in step (2), the particle size of the Al2O3 powder can be 400-600 nm, and the resistivity regulator can include at least one of TiO2, SnO2, ZnO, In2O3, and Ga2O3.

[0024] If the particle size of Al2O3 powder is too large, the particle core will be difficult to be wetted by the colorant, resulting in uneven coloring; while if the particle size of nanoparticles is too small, the surface energy is high and they are very easy to agglomerate, resulting in uneven color spots in the sintered sample, showing uneven coloring and high reflectivity.

[0025] In some embodiments, in step (2), with the total mass of Al2O3 powder, the black pigment, and the resistivity regulator being 100%, the mass percentage of Al2O3 can be 70-98%, the mass percentage of the black pigment can be 0-20%, and the mass percentage of the resistivity regulator can be 0-20%.

[0026] In some cases, too low a content of black pigment will prevent the sample from exhibiting a black color, while too high a content will result in a spinel-dominated sample system, leading to poor mechanical properties. Furthermore, since the raw material for black pigment is a transition metal oxide, its unit price is higher than that of the base material, alumina. Adding too much black pigment will increase costs and is not conducive to industrial production; therefore, the optimal proportion of black pigment is 0-20%. The resistivity of ceramics does not decrease indefinitely with increasing resistivity modifier content; excessive resistivity modifier can actually alter the structure of Al2O3 ceramics, affecting their practical applications. Moreover, the cost of resistivity modifiers is also higher than that of Al2O3; therefore, their optimal addition range is 0-20%.

[0027] In some embodiments, in step (2), the mixing method can be ball milling; wherein, in the ball milling process, the mass ratio of raw material to ball mill can be 1:3.5, the ball milling time can be 20-30h, the rotation speed can be 200-250r / min, and the solvent can be anhydrous ethanol; preferably, the slurry after ball milling is dried and sieved, the drying temperature can be 50-60℃, the drying time can be 36-48h, and the sieve mesh size can be 80-100.

[0028] In some embodiments, in step (2), the molding method may include dry pressing and cold isostatic pressing; preferably, the pressure of cold isostatic pressing may be 100-200 MPa.

[0029] In some embodiments, in step (2), the temperature of the glue removal can be 600-800℃, the heating rate can be 1-2℃ / min, the holding time can be 2-5h, and the atmosphere for glue removal can be air, vacuum or nitrogen.

[0030] In some embodiments, in step (2), the sintering process may include: raising the temperature to 800-1000℃ at 3-5℃ / min and holding for 2-3 hours, then raising the temperature to 1500-1600℃ at 1-2℃ / min and holding for 3-5 hours, then lowering the temperature to 800-1000℃ at 1-2℃ / min, then lowering the temperature to 500-600℃ at 3-5℃ / min, and finally lowering to room temperature; preferably, the sintering atmosphere may include air, vacuum or nitrogen.

[0031] In this sintering process, a relatively fast sintering rate is used in the early stage to help eliminate internal pores in the ceramic; a slow heating rate is used in the later stage to ensure a uniform temperature field and liquid phase distribution within the ceramic, allowing for slow grain growth. The optimal sintering temperature is controlled within 1500-1600℃. Too low a sintering temperature not only results in lower ceramic density but also prevents the colorant transition metal ions from completely dissolving in Al2O3, leading to a lower black hue. Too high a sintering temperature causes some of the black spinel second phase to volatilize, further reducing the black hue. Furthermore, excessively high sintering temperatures can lead to abnormal grain growth, resulting in reduced mechanical properties and impacting practical applications.

[0032] This invention proposes a method that uses black spinel as a pigment and is supplemented with a resistivity regulator to achieve synergistic control of the black color and resistivity of ceramics. Moreover, by changing the content of black pigment and resistivity regulator, the black color and antistatic function of alumina ceramics can be independently or synergistically controlled to meet practical application requirements.

[0033] In some embodiments, the resistivity-tunable black alumina ceramic obtained by the preparation method provided by the present invention can achieve an absorbance of 95% and a volume resistivity of 10.5 ~10 12 Ω·cm.

[0034] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art.

[0035] Example 1 The method for preparing resistivity-tunable black alumina ceramic provided in this embodiment includes the following steps: (1) Weigh 65g MnO2, 20g Fe2O3, 8.5g NiO, 4.5g CoO, 2g Cr2O3 and 100g anhydrous ethanol. The above raw materials are ball-milled with 350g ball mill at 220r / min for 24h. The slurry after ball milling is dried in an oven at 60℃ for 48h and then passed through a 100-mesh sieve to obtain a black powder. The black powder was placed in a muffle furnace and heated to 1100℃ at a rate of 3℃ / min. After holding at this temperature for 3 hours, a black pigment was obtained. (2) Weigh 90g Al2O3, 10g black pigment and 100g anhydrous ethanol, and ball mill the above powder with 350g ball mill at 220r / min for 24h. After ball milling, dry the slurry in an oven at 60℃ for 48h and pass it through a 100-mesh sieve to obtain black alumina powder. Black alumina powder was dry-pressed, and then cold isostatically pressed at 100 MPa to obtain a black ceramic green body. The green body was placed in a muffle furnace and heated to 600℃ at 2℃ / min and held for 2 hours. Then it was transferred to another high-temperature muffle furnace and heated to 1000℃ at 3℃ / min and held for 2 hours. Then it was heated to 1500℃ at 2℃ / min and held for 3 hours. Then it was cooled to 1000℃ at 2℃ / min and then to 600℃ at 5℃ / min. Finally, it was cooled to room temperature to obtain black alumina ceramic.

[0036] Example 2 The method for preparing the resistivity-tunable black alumina ceramic provided in this embodiment is the same as in Embodiment 1, with the main difference being: In step (2), 90g Al2O3, 10g TiO2 and 100g anhydrous ethanol are added for ball milling; the sintering atmosphere for the black ceramic is vacuum.

[0037] Example 3 The method for preparing the resistivity-tunable black alumina ceramic provided in this embodiment is the same as in Embodiment 1, with the main difference being: In step (2), 90g Al2O3, 4g black pigment, 6g TiO2 and 100g anhydrous ethanol are added and ball-milled.

[0038] Example 4 The method for preparing the resistivity-tunable black alumina ceramic provided in this embodiment is the same as in Embodiment 1, with the main difference being: In step (2), 90g Al2O3, 8g black pigment, 2g TiO2 and 100g anhydrous ethanol are added and ball-milled.

[0039] Example 5 The method for preparing black alumina ceramics provided in this embodiment includes the following steps: (1) Weigh 1.3g MnO2, 0.4g Fe2O3, 0.17g NiO, 0.09g CoO, 0.04g Cr2O3, 90g Al2O3, 8g TiO2 and 100g anhydrous ethanol. The above powders are ball-milled with 350g ball mill at 220r / min for 24h. The slurry after ball milling is dried in an oven at 60℃ for 48h and then passed through a 100-mesh sieve to obtain black alumina powder. (2) The black alumina powder was dry-pressed and then cold isostatically pressed at 100 MPa to obtain a black ceramic blank. The blank was placed in a debinding furnace and heated to 600°C at 2°C / min and held for 2 hours. Then it was transferred to another high-temperature sintering furnace and heated to 1000°C at 3°C / min and held for 2 hours. Then it was heated to 1500°C at 2°C / min and held for 3 hours. Then it was cooled to 1000°C at 2°C / min and then cooled to 600°C at 5°C / min. Finally, it was cooled to room temperature to obtain black alumina ceramic.

[0040] Example 6 The method for preparing black alumina ceramics provided in this embodiment includes the following steps: (1) Weigh 5.2g MnO2, 1.6g Fe2O3, 0.68g NiO, 0.36g CoO, 0.16g Cr2O3, 90g Al2O3, 2g TiO2, and 100g anhydrous ethanol. Grind the above powders with 350g of ball milling machine at 220r / min for 24h. Dry the slurry after ball milling in a 60℃ oven for 48h, and pass it through a 100-mesh sieve to obtain black alumina powder. (2) The black alumina powder was dry-pressed and then cold isostatically pressed at 100 MPa to obtain a black ceramic blank. The blank was placed in a debinding furnace and heated to 600°C at 2°C / min and held for 2 hours. Then it was transferred to another high-temperature sintering furnace and heated to 1000°C at 3°C / min and held for 2 hours. Then it was heated to 1500°C at 2°C / min and held for 3 hours. Then it was cooled to 1000°C at 2°C / min and then cooled to 600°C at 5°C / min. Finally, it was cooled to room temperature to obtain black alumina ceramic.

[0041] Example 7 The method for preparing the resistivity-tunable black alumina ceramic provided in this embodiment is the same as in Embodiment 1, with the main difference being: In step (2), the maximum sintering temperature is 1400℃.

[0042] L, a, and b represent the chromaticity values ​​of the object's color, i.e., the color space coordinates of that color. Every color has a unique coordinate value, where L represents lightness / darkness (black and white), a represents red / green, and b represents yellow / blue. Tests show that the black alumina ceramic prepared by this invention exhibits a uniform black color and low reflectivity. Specifically, the blackness of Examples 1-4 is all above 30, and the values ​​of a and b are close to 0, indicating that the black alumina ceramic prepared by this invention has high blackness. Comparing the reflectivity data of Examples 1, 3, and 4 shows that the blackness value increases with increasing black pigment content. The volume resistivity test results of Examples 1-4 show that with increasing TiO2 content (0-10%), the volume resistivity gradually decreases (8.94 × 10⁻⁶) while maintaining low light reflectivity. 11 -1.08×10 5 The reflectance of the black ceramic is Ω·cm, indicating an improvement in its antistatic properties. Comparing Examples 4 and 6, it is evident that, with the same colorant content, the black alumina ceramic prepared using the one-step synthesis method exhibits increased reflectance and volume resistivity. This is due to the volatilization of the coloring oxides and the introduction of pores during sintering, leading to uneven coloring and increased volume resistivity. Furthermore, in Example 5, even with an increase of 2% TiO2, the resistivity remains on the same order of magnitude as in Example 3, and a uniform black color cannot be guaranteed, further illustrating the advantages of this invention. Further comparison of Examples 1 and 7 shows that the lower sintering temperature of this invention results in increased ceramic reflectance and reduced black chroma in the sample. In summary, this invention, through pre-synthesizing black ceramic pigment and synergistically controlling the black chroma and volume resistivity of the ceramic with a resistivity regulator, further meets the requirements of the national standard GB 26539-2011 for antistatic ceramics (volume resistivity 5×10⁻⁶). 4 -1×10 9 Ω·cm).

[0043] Table 1 below shows the raw material ratios and test results in different embodiments: raw material Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 <![CDATA[MnO2]]> 65 65 65 65 1.3 5.2 65 <![CDATA[Fe2O3]]> 20 20 20 20 0.4 1.6 20 NiO 8.5 8.5 8.5 8.5 0.17 0.68 8.5 CoO 4.5 4.5 4.5 4.5 0.09 0.36 4.5 <![CDATA[Cr2O3]]> 2 2 2 2 0.04 0.16 2 <![CDATA[Al2O3]]> 90 90 90 90 90 90 90 Black pigment 10 0 4 8 / / 10 <![CDATA[TiO2]]> 0 10 6 2 8 2 0 Black pigment sintering atmosphere Air Air Air Air / / Air De-glue atmosphere Air Air Air Air Air Air Air Black ceramic sintering atmosphere Air vacuum Air Air Air Air Air Sintering temperature (°C) 1500 1500 1500 1500 1500 1500 1400 Volume resistivity (Ω·cm) <![CDATA[8.94×10 11 ]]> <![CDATA[1.08×10 5 ]]> <![CDATA[2.3×10 8 ]]> <![CDATA[4.09×10 9 ]]> <![CDATA[7.69×10 8 ]]> <![CDATA[1.09×10 12 ]]> <![CDATA[5.71×10 12 ]]> Visible light range reflectance (%) 4.4-7.5 6.5-12.57 5.3-9.51 4.52-9.83 5.38-15.35 4.46-9.69 9.48-18.59 L 33.65 34.9 29.3 31.14 27.62 34.29 23.17 a 0.18 0.13 0.68 0.33 1.81 0.98 3.14 b 0.98 -8.37 0.93 0.83 3.4 4.84 5.49 Appearance uniform black uniform black uniform black uniform black Uneven blackish-gray Uneven black uniform brown

[0044] Figure 1 The image shows a polished surface of the black alumina ceramic prepared in Example 1. As can be seen from the image, the alumina ceramic exhibits a uniform black color and has no obvious internal impurities.

[0045] Figure 2 The graph shows a comparison of the reflectance of the alumina ceramic materials prepared in Examples 1-7. As can be seen from the graph, Examples 1, 3, and 4 have lower reflectance, indicating higher black hue; while Examples 5 and 6, prepared using a one-step synthesis method, show significantly higher reflectance. Furthermore, although Example 7 uses the same formula as Example 1, its lower sintering temperature prevents transition metal ions from dissolving in alumina, thus also resulting in higher reflectance.

[0046] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for preparing a black alumina ceramic with adjustable resistivity, characterized in that, The preparation method includes the following steps: (1) MnO2, Fe2O3, NiO, CoO and Cr2O3 powders were mixed and calcined to obtain a black pigment; (2) The Al2O3 powder is mixed with the black pigment and resistivity regulator to obtain black alumina raw material powder, and then the powder is shaped, debinded and sintered to obtain the black alumina ceramic with adjustable resistivity.

2. The preparation method according to claim 1, characterized in that, In step (1), based on a total mass percentage of 100%, the mass percentage of MnO2 is 55-70%, the mass percentage of Fe2O3 is 10-25%, the mass percentage of NiO is 6-10%, the mass percentage of CoO is 4-8%, and the mass percentage of Cr2O3 is 2-6%.

3. The preparation method according to claim 1 or 2, characterized in that, In step (1), the mixing method is ball milling; wherein, in the ball milling process, the mass ratio of raw material to ball mill is 1:3.5, the ball milling time is 20-30h, the rotation speed is 200-250r / min, and the solvent is anhydrous ethanol; preferably, the slurry after ball milling is dried and sieved, the drying temperature is 50-60℃, the drying time is 36-48h, and the sieve mesh size is 80-100.

4. The preparation method according to any one of claims 1-3, characterized in that, In step (1), the heating rate of calcination is 2-5℃ / min, the calcination temperature is 1000-1200℃, the holding time is 2-5h, and the calcination atmosphere is air, vacuum, or nitrogen.

5. The preparation method according to any one of claims 1-4, characterized in that, In step (2), the particle size of the Al2O3 powder is 400-600 nm, and the resistivity regulator includes at least one of TiO2, SnO2, ZnO, In2O3, and Ga2O3.

6. The preparation method according to any one of claims 1-5, characterized in that, In step (2), with the total mass of Al2O3 powder, black pigment, and resistivity regulator as 100%, the mass percentage of Al2O3 is 70-98%, the mass percentage of black pigment is 0-20%, and the mass percentage of resistivity regulator is 0-20%.

7. The preparation method according to any one of claims 1-6, characterized in that, In step (2), the mixing method is ball milling; wherein, in the ball milling process, the mass ratio of raw material to ball mill is 1:3.5, the ball milling time is 20-30h, the rotation speed is 200-250r / min, and the solvent is anhydrous ethanol; preferably, the slurry after ball milling is dried and sieved, the drying temperature is 50-60℃, the drying time is 36-48h, and the sieve mesh size is 80-100.

8. The preparation method according to any one of claims 1-7, characterized in that, In step (2), the molding method includes dry pressing and cold isostatic pressing; preferably, the pressure of cold isostatic pressing is 100-200 MPa; The temperature for discharging the adhesive is 600-800℃, the heating rate is 1-2℃ / min, the holding time is 2-5h, and the atmosphere for discharging the adhesive is air, vacuum, or nitrogen.

9. The preparation method according to any one of claims 1-8, characterized in that, In step (2), the sintering process includes: raising the temperature to 800-1000℃ at 3-5℃ / min and holding for 2-3 hours, then raising the temperature to 1500-1600℃ at 1-2℃ / min and holding for 3-5 hours, then lowering the temperature to 800-1000℃ at 1-2℃ / min, then lowering the temperature to 500-600℃ at 3-5℃ / min, and finally lowering to room temperature; preferably, the sintering atmosphere includes air, vacuum or nitrogen.

10. A black alumina ceramic with adjustable resistivity obtained by the preparation method according to any one of claims 1-9.

Images