A rapid pressureless sintering method for preparing a wide-band high-transparency AlON ceramic

Abstract

This invention relates to a rapid pressureless sintering preparation method for broadband high-transmittance AlON ceramics, belonging to the field of transparent ceramic material preparation. The invention involves ball milling and mixing Y₂O₃ raw material powder and AlON raw material powder to obtain an AlON / Y₂O₃ mixed powder; then, the AlON / Y₂O₃ mixed powder is pressurized to obtain a green body; finally, the green body is pressureless sintered to obtain broadband high-transmittance AlON transparent ceramics. In the AlON / Y₂O₃ mixed powder, Y₂O₃ powder is uniformly distributed in the mixed powder in the form of single particles and clusters composed of 2-5 and 6-60 single particles, with the mass of the Y₂O₃ powder in the form of clusters of 6-60 single particles being 50%-80% of the total Y₂O₃ raw material powder. This invention is simple to operate, has a short pressureless sintering holding time, high efficiency, good energy-saving effect, and low cost. Furthermore, the prepared AlON ceramics exhibit high transmittance in both the visible and infrared bands, making it suitable for industrial production.

Description

Technical Field

[0001] This invention relates to a rapid pressureless sintering preparation method for broadband high-transmittance AlON ceramics, belonging to the field of transparent ceramic material preparation. Background Technology

[0002] AlON (aluminum oxynitride) transparent ceramics have a cubic spinel structure and are optically isotropic. They combine high light transmittance with good mechanical properties, making them one of the most promising structural-functional integrated transparent ceramic window materials. They can be widely used in transparent armor, infrared detection, and protective windows, and have broad application prospects in both national defense and civilian fields.

[0003] Among various ceramic sintering methods, pressureless sintering has the advantages of readily available equipment and low cost, and it also has unique advantages in product size scaling. Therefore, under the premise of ensuring product performance, pressureless sintering has become the preferred method for sintering and preparing ceramic materials. Similarly, for the preparation of AlON transparent ceramics, it is hoped that AlON ceramics with excellent light transmittance can be obtained solely through pressureless sintering. However, in the process of preparing ceramics by sintering AlON powder, AlON can first decompose to form α-Al₂O₃ (alumina) and AlN (aluminum nitride), and then reform AlON under higher temperature conditions. This process is affected by the coupled effects of multiple factors such as AlON powder particle size, sintering aids and their dosage. These effects may lead to problems such as unsatisfactory microstructure formed in the early and middle stages of sintering and insufficient sintering driving force in the later stages of sintering, which in turn makes it extremely difficult to remove pores in the high-density sintering stage in the later stages of sintering. Therefore, the pressureless sintering preparation of AlON transparent ceramics often requires holding at high temperature (1880~2000℃) for 7~30h to effectively remove pores and obtain better light transmittance.

[0004] Therefore, to efficiently expel pores and achieve rapid preparation of high-transmittance AlON ceramics, it is necessary to control the degree of AlON decomposition in the early and middle stages of sintering to avoid particle agglomeration / coarsening caused by excessive α-Al₂O₃, while ensuring sufficient sintering driving force in the later stages to promote effective expulsion of small pores within a short holding time. Thus, controlling the sintering aid and AlON powder particle size, and managing their synergistic effect to control the phase transformation and microstructure evolution throughout the sintering process, while ensuring a good microstructure in the early and middle stages, and further utilizing the sintering aid to provide sufficient driving force for the later high-density sintering, should be an effective way to obtain high-density and high-transmittance AlON ceramics. Summary of the Invention

[0005] The purpose of this invention is to provide a rapid pressureless sintering preparation method for broadband high-transmittance AlON ceramics. Specifically, a porous precursor is first prepared using yttrium nitrate, citric acid, and ethylene glycol. Then, nano-Y₂O₃ powder with clustered characteristics is obtained through calcination. The obtained Y₂O₃ powder is then mixed with AlON powder, and broadband high-transmittance AlON ceramics are prepared by pressureless sintering under a nitrogen atmosphere. The clustered nano-Y₂O₃ powder can be uniformly distributed within the AlON powder, avoiding localized over-enrichment. This prevents excessive decomposition of AlON to generate excessive α-Al₂O₃ in the early and middle stages of sintering, resulting in a better microstructure in the ceramic before the later stages of sintering. Furthermore, the clustered Y₂O₃ ensures a sufficient concentration of Y in the ceramic to promote sintering densification, maintaining densification capability even in the later stages of sintering and facilitating the efficient removal of small-sized pores. Therefore, during the later heat preservation stage, pores are continuously expelled, thus achieving rapid pressureless sintering preparation of AlON ceramics with high light transmittance over a wide wavelength range. This method features short high-temperature heat preservation time, high efficiency, good energy-saving effect, low cost, and simple operation, making it easy to scale up production.

[0006] A rapid pressureless sintering preparation method for broadband high-transmittance AlON ceramics involves ball milling and mixing Y₂O₃ raw material powder and AlON raw material powder, followed by drying and granulation to obtain an AlON / Y₂O₃ mixed powder. The AlON / Y₂O₃ mixed powder is then pre-formed under unidirectional pressure, followed by cold isostatic pressing to obtain a green body. Finally, the green body is pressureless sintered under a nitrogen atmosphere to obtain broadband high-transmittance transparent AlON ceramics.

[0007] In the AlON / Y2O3 mixed powder, the Y2O3 powder is uniformly distributed in the mixed powder in the form of single particles and clusters composed of 2 to 5 and 6 to 60 single particles. The mass of the Y2O3 powder in the form of clusters composed of 6 to 60 single particles is 50% to 80% of the Y2O3 raw material powder.

[0008] In the method described in this invention, the Y2O3 powder in the AlON / Y2O3 mixed powder exists in three forms: single particles, small clusters composed of 2 to 5 single particles, and large clusters composed of 6 to 60 single particles.

[0009] The mass of Y2O3 powder in the form of large clusters composed of 6 to 60 individual particles is 50% to 80% of that of Y2O3 raw material powder.

[0010] In the method described in this invention, different forms of Y2O3 powder are uniformly distributed in the AlON / Y2O3 mixed powder, which can limit the degree of AlON decomposition in the early and middle stages of sintering and control the α-Al2O3 content in the sample to a low level, thereby preventing particle agglomeration / coarsening before entering the later stage of sintering.

[0011] In the method described in this invention, the Y2O3 powder in the form of large clusters composed of 6 to 60 single particles can ensure that the ceramic has a sufficient concentration of yttrium (Y) to promote sintering densification, so that the pores of AlON can still be efficiently discharged in the later stage of sintering, thereby achieving the preparation of wide-band high light transmittance AlON ceramics through pressureless sintering under relatively short holding time conditions.

[0012] In the method described in this invention, the primary particle size of the Y₂O₃ raw material powder is 20–100 nm, the primary average particle size is 30–70 nm, and the specific surface area is 20–30 m². 2 / g.

[0013] In the method described in this invention, the Y2O3 raw material powder can be first ball-milled in anhydrous ethanol at a speed of 150-180 rpm for 8-14 hours using silicon nitride balls with a diameter of 3-5 mm, and then mixed with AlON powder. The ball-to-powder ratio of the ball-milled Y2O3 raw material powder is 8-11:1.

[0014] In the method described in this invention, the Y2O3 raw material powder can be obtained by the following method:

[0015] S1: Weigh yttrium nitrate and citric acid in a molar ratio of 1:3, add 50 mL of deionized water, and stir to dissolve until a clear solution is formed;

[0016] S2: Weigh ethylene glycol according to the molar ratio of citric acid to ethylene glycol 3:1, add it to the transparent solution obtained in S1, heat it in an oil bath to 70-90°C, and stir continuously until a viscous sol is formed.

[0017] S3: The viscous sol obtained in S2 is kept in an oven at 70-90℃ for 20-26 hours to form a gel;

[0018] S4: The gel obtained in S3 is heated to 220-250℃ in a muffle furnace at a rate of 5-30℃ / min and held for 1-4 hours to foam and form a porous precursor.

[0019] S5: Grind the porous precursor, pass it through a 50-mesh sieve, and heat it in a muffle furnace to 850-950℃ at a rate of 10-20℃ / min and hold it for 1-4 hours to obtain pure phase Y2O3 powder.

[0020] Furthermore, the purity of the yttrium nitrate is ≥99.99%, the purity of the citric acid is ≥99.5%, and the purity of the ethylene glycol is ≥99%.

[0021] In the method described in this invention, the Y2O3 raw material powder and the AlON raw material powder are first ball-milled at 150-180 rpm for 12-14 hours, and then ball-milled at 180-240 rpm for 16-20 hours to obtain AlON / Y2O3 mixed powder.

[0022] Furthermore, the amount of Y2O3 raw material powder is 0.2 to 0.4% of the mass of AlON raw material powder.

[0023] Furthermore, the D of the obtained AlON / Y2O3 mixed powder 50 The particle size ranges from 0.8 to 1.4 μm, with a particle size distribution range of 0.05 to 8.0 μm.

[0024] The ball milling operations described in this invention are all performed in devices provided by existing technology, preferably planetary ball mills.

[0025] In the method described in this invention, the unidirectional pressure preforming is completed at 30-60 MPa, and the cold isostatic pressing is completed at 100-180 MPa.

[0026] In the method described in this invention, the heating rate of the pressureless sintering is 10-30℃ / min, the sintering temperature is 1860-1900℃, and the holding time is 3.5-5.5h.

[0027] A preferred technical solution of the present invention:

[0028] ① Preparation of nano-Y2O3 raw material powder: Weigh yttrium nitrate and citric acid, add deionized water, and stir to dissolve until a transparent solution is formed; add ethylene glycol, heat in an oil bath, and stir continuously until a viscous sol is formed; keep warm in an oven to form a gel; then calcine in a muffle furnace to foam and form a porous precursor; grind the porous precursor, sieve, and continue calcining in a muffle furnace to obtain pure phase Y2O3 powder;

[0029] ② Raw material mixing: The Y2O3 raw material powder obtained in step ① is first ball-milled, and then AlON powder and the ball-milled Y2O3 powder obtained above are weighed and placed in a ball milling jar. The two are ball-milled and mixed in anhydrous ethanol with silicon nitride balls as the grinding medium to obtain a slurry. After drying and granulation, AlON / Y2O3 mixed powder is obtained.

[0030] ③ Green body forming: The AlON / Y2O3 mixed powder obtained in step ② is first pre-formed by unidirectional pressure, and then cold isostatically pressed to obtain the green body;

[0031] ④ Pressureless sintering: The green body obtained in step ③ is placed in a vacuum atmosphere graphite furnace and pressureless sintered under a nitrogen atmosphere to prepare AlON transparent ceramics.

[0032] Preferably, the rapid pressureless sintering preparation method of the wide-band high-transmittance AlON transparent ceramic includes a post-processing step: grinding and polishing the transparent ceramic obtained in step ④.

[0033] Another object of the present invention is to provide AlON transparent ceramics prepared by the above method.

[0034] The AlON transparent ceramic obtained by this invention has a transmittance of ≥80% in the 350-4480nm wavelength range, a maximum transmittance of 87.5%, a transmittance of 81.2% at 400nm, and HV>17GPa.

[0035] The beneficial effects of this invention are as follows: By preparing nano-Y2O3 powder with certain cluster characteristics and using it as a sintering aid to prepare transparent AlON ceramics, the invention achieves a uniform overall distribution of Y2O3 while utilizing clustered Y2O3 to ensure that the ceramics still have good densification sintering ability in the later stages of sintering. On the one hand, the uniform overall distribution of Y2O3 (avoiding excessively high local Y concentrations) can limit the degree of AlON decomposition in the early and middle stages of sintering, controlling the α-Al2O3 content in the sample to a low level, thereby preventing particle agglomeration / coarsening before entering the later stages of sintering. On the other hand, the clustered Y2O3 particles can ensure that there is a sufficient concentration of Y in the ceramic to promote sintering densification, allowing AlON to still be efficiently discharged from the pores in the later stages of sintering. Thus, a wide-band high-transmittance AlON ceramic can be prepared by pressureless sintering under short holding time conditions. The ceramic preparation process of this invention has a short holding time; the ceramic obtained after holding for 4 hours has the advantages of a wide range of high transmittance wavelengths and high transmittance. The ceramic prepared by this invention exhibits a transmittance of ≥80% in the 350–4480 nm wavelength range, with a maximum transmittance of 87.5%, and a transmittance of 81.2% at 400 nm. Furthermore, this ceramic possesses high hardness, with HV > 17 GPa. The preparation process of the clustered Y₂O₃ powder in this invention is simple and low-cost; the pressureless sintering equipment is readily available and has low investment costs; the sintering process involves short holding time, resulting in good energy-saving effects, high efficiency, and low preparation costs, making it easy to industrialize; the prepared ceramic has a wide wavelength transmission range and good light transmittance, offering broader application prospects. Attached Figure Description

[0036] Figure 1 (a) XRD patterns of Y2O3 powder obtained in Example 1, Y2O3 powder used in Comparative Example 1 and Comparative Example 2; Figure 1 (b) is a SEM image of the Y2O3 powder obtained in Example 1; Figure 1 (c) is a SEM image of the Y2O3 powder used in Comparative Example 1; Figure 1 (d) is a SEM image of the Y2O3 powder used in Comparative Example 2.

[0037] Figure 2This is a TEM image of the Y2O3 powder obtained in Example 1.

[0038] Figure 3 (a) and (b) are SEM images and EDS distribution diagrams of the AlON / Y2O3 mixed powder after ball milling in Example 1; Figure 3 (c) and (d) are SEM images and EDS distribution diagrams of the AlON / Y2O3 mixed powder after ball milling in Comparative Example 1. Figure 3 (e) and (f) are SEM images and EDS distribution diagrams of Y element in the AlON / Y2O3 mixed powder after ball milling in Comparative Example 2.

[0039] Figure 4 The transmittance curves are for the AlON transparent ceramics obtained in Example 1, Comparative Example 1, and Comparative Example 2.

[0040] Figure 5 The fracture morphology images are of the AlON transparent ceramics obtained in Example 1(a), Comparative Example 1(b), and Comparative Example 2(c).

[0041] Figure 6 The graph shows the change in α-Al2O3 content during the heating process of the AlON transparent ceramics obtained in Example 1, Comparative Example 1, and Comparative Example 2.

[0042] Figure 7 The diagram shows the microstructure evolution process of the AlON transparent ceramics obtained in Example 1, Comparative Example 1, and Comparative Example 2 during the heating process.

[0043] Figure 8 The graph shows the densification process curves of the AlON transparent ceramics obtained in Example 1, Comparative Example 1, and Comparative Example 2. Detailed Implementation

[0044] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the invention, but do not limit the invention in any way.

[0045] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; the reagents and materials described are commercially available unless otherwise specified.

[0046] One of the specific implementation methods:

[0047] ① Preparation of nano-Y2O3 raw material powder:

[0048] S1: Weigh yttrium nitrate and citric acid in a molar ratio of 1:3, add 50 mL of deionized water, and stir to dissolve until a clear solution is formed;

[0049] S2: Weigh ethylene glycol according to the molar ratio of citric acid to ethylene glycol 3:1, add it to the transparent solution obtained in S1, heat it in an oil bath to 70-90°C, and stir continuously until a viscous sol is formed.

[0050] S3: The viscous sol obtained in S2 is kept in an oven at 70-90℃ for 20-26 hours to form a gel;

[0051] S4: The gel obtained in S3 is heated to 220-250℃ in a muffle furnace at a rate of 5-30℃ / min and held for 1-4 hours to foam and form a porous precursor.

[0052] S5: Grind the porous precursor, pass it through a 50-mesh sieve, and heat it in a muffle furnace at 10-20℃ / min to 850-950℃ and hold it for 1-4 hours to obtain pure phase Y2O3 powder.

[0053] ② Raw material mixing: The Y2O3 raw material powder obtained in step (1) is ball-milled in anhydrous ethanol at a speed of 150-180 rpm for 8-14 hours using silicon nitride balls with a diameter of 3-5 mm to obtain ball-milled Y2O3 powder. The ball-to-material ratio of the ball-milled Y2O3 raw material powder is 8-11:1. Then, AlON powder and the ball-milled Y2O3 powder obtained in the above steps are weighed, wherein the amount of Y2O3 powder is 0.2-0.4% of the mass of AlON powder. The two are placed in a ball milling jar and ball-milled in anhydrous ethanol at 150-180 rpm for 12-14 hours using silicon nitride balls as the grinding medium. Then, the mixture is ball-milled at 180-240 rpm for 16-20 hours to obtain a slurry. After drying and granulation, AlON / Y2O3 mixed powder is obtained.

[0054] ③ Green body forming: The AlON / Y2O3 mixed powder obtained in step (2) is first pre-formed by unidirectional pressure at 30-60MPa, and then cold isostatically pressed at 100-180MPa to obtain the green body;

[0055] ④ Pressureless sintering: The green body obtained in step (3) is placed in a vacuum atmosphere graphite furnace and heated to 1860-1900℃ at 10-30℃ / min under nitrogen atmosphere and held for 3.5-5.5h to prepare AlON transparent ceramics by pressureless sintering.

[0056] ⑤ Processing: Grinding and polishing the AlON transparent ceramic.

[0057] Example 1

[0058] A rapid pressureless sintering method for preparing broadband high-transmittance AlON ceramics

[0059] First, weigh 3.8301g of yttrium nitrate (99.99% purity) and 5.7636g of citric acid (99.5% purity), add 50mL of deionized water, and stir until a transparent solution is formed. Then, add 0.62g of ethylene glycol (99% purity), heat the resulting solution to 80℃ in an oil bath, and stir continuously until a viscous sol is formed. Then, continue to keep it at 80℃ in an oven for 24h to form a gel. Transfer the gel to a muffle furnace, heat it to 240℃ at 10℃ / min and keep it at that temperature for 2h to form a porous precursor through foaming. Grind the porous precursor, pass it through a 50-mesh sieve, and place it in a muffle furnace, heat it to 900℃ at 10℃ / min and keep it at that temperature for 2h to obtain Y2O3 raw material powder.

[0060] The phase composition and microstructure of the prepared Y2O3 raw material powder are shown in the figure. Figure 1 (a), (b) and Figure 2 This indicates that pure-phase Y2O3 powder was obtained, and the primary particle size of the powder is granular, with multiple particles forming clusters.

[0061] The Y₂O₃ powder obtained above was ball-milled at 170 rpm for 12 hours using a planetary ball mill. The grinding balls used were silicon nitride balls with a diameter of 4 mm, and the ball-to-powder ratio was 10:1. After ball milling, the primary particle size of the Y₂O₃ powder was 20–100 nm, the average particle size was 51 nm, and the specific surface area was 25 m². 2 / g.

[0062] AlON powder and the ball-milled Y₂O₃ powder (0.3 wt.%) were weighed and ball-milled in anhydrous ethanol at 170 rpm for 12 h using silicon nitride balls as the milling medium. The milling speed was then increased to 210 rpm, and the mixture was continued for 18 h. The morphology and Y element distribution of the resulting AlON / Y₂O₃ powder after ball milling are shown in [Figure / Reference]. Figure 3 As shown in (a) and (b), the different forms of Y2O3 powder are relatively evenly distributed in the mixed powder, and Y2O3 clusters composed of approximately 40 Y2O3 individual particles can be observed. In the AlON / Y2O3 powder obtained after ball milling and mixing, the mass of Y2O3 clusters composed of 6 to 60 individual particles accounts for 64% of the mass of the Y2O3 raw material powder.

[0063] The ball-milled AlON / Y2O3 mixed powder was first pre-formed under 50 MPa pressure for 5 min, and then cold isostatically pressed at 120 MPa to obtain a green body. The green body was placed in a graphite furnace and heated to 1880℃ at 15℃ / min in a nitrogen atmosphere, and held for 4 h to obtain AlON transparent ceramic. The prepared AlON transparent ceramic was ground and polished to a thickness of 2 mm on both sides, and the transmittance was measured. Figure 4The transmittance curve of the prepared AlON transparent ceramic shows that the prepared AlON ceramic has good light transmittance. The transmittance is ≥80% in a wide wavelength range of 350-4480nm, the maximum transmittance is 87.5% (3600nm), and the transmittance at 400nm is 81.2%. Figure 5 (a) is a fracture morphology diagram of the prepared AlON transparent ceramic. It can be seen that no obvious pores were observed in the prepared AlON transparent ceramic. Figure 6 The graph shows the change in α-Al2O3 content during the heating process. It can be seen that the content of α-Al2O3 produced by the decomposition of AlON remains at a low level (22 wt.%). Figure 7 The image shows the changes in fracture morphology during the heating process. It can be seen that no obvious particle agglomeration / coarsening phenomenon occurred during the heating process of this ceramic. Figure 8 The densification process curve shows that the ceramic has a good densification effect during the heating process, and the relative density of the ceramic reaches 99.85% after heat preservation and sintering.

[0064] Comparative Example 1

[0065] Comparative Example 1 followed the method of Example 1, except that the average particle size of the nano-Y2O3 was 30.4 nm, and the particles were in a soft aggregate state (see Example 1). Figure 1 (a) and (c)), all other experimental conditions were the same as in Example 1. Compared with Example 1, Y2O3 was more uniformly distributed in the ball-milled AlON / Y2O3 mixed powder, and the locally enriched Y2O3 consisted of smaller and fewer particles (see Example 1). Figure 3 (c) and (d)). The wavelength range of the prepared AlON with a transparency transmittance ≥80% is 370–4200 nm, the maximum infrared transmittance is 83.3%, and the transmittance at 400 nm is 80.4%. The results are shown in […]. Figure 4 The fracture morphology of the ceramic obtained by this method shows that pores can be observed. Figure 5 (b) The α-Al2O3 content was low during the heating process. Figure 6 No local particle aggregation / coarsening was observed in the early and middle stages of sintering. Figure 7 The densification process is relatively fast during the heating stage. Figure 8 The relative density of the ceramic after heat preservation sintering is 99.74%.

[0066] Comparative Example 2

[0067] Comparative Example 2 follows the method of Example 1, except that the Y2O3 sintering aid used is a pure-phase micron-sized lamellar powder. Figure 1 (a) and (d)). Severe local enrichment of Y2O3 was observed in the ball-milled AlON / Y2O3 mixed powder. Figure 3(e) and (f)). The transmittance curves of the prepared AlON transparent ceramics are shown in (e) and (f). Figure 4 The transmission range is narrow, with transmittance ≥80% only in the 2440–4150 nm band, a maximum transmittance of 82.8%, and a transmittance of 66.9% at 400 nm. The fracture morphology of the ceramics obtained by this method shows a large number of large-sized pores. Figure 5 (c) The α-Al2O3 content is relatively high during the heating process. Figure 6 This leads to localized particle aggregation / coarsening in the early stages of sintering. Figure 7 The densification process is relatively slow in the early and middle stages of sintering. Figure 8 As a result, the relative density of the sample after heat preservation and sintering was also low (99.41%).

Claims

1. A rapid pressureless sintering preparation method for broadband high-transmittance AlON ceramics, characterized in that: Y₂O₃ raw material powder and AlON raw material powder were ball-milled and mixed, then dried and granulated to obtain AlON / Y₂O₃ mixed powder. The AlON / Y₂O₃ mixed powder was then pre-formed under unidirectional pressure, followed by cold isostatic pressing to obtain a green body. Finally, the green body was pressurelessly sintered under a nitrogen atmosphere to obtain a broadband high-transmittance AlON transparent ceramic. In the AlON / Y2O3 mixed powder, the Y2O3 powder is uniformly distributed in the mixed powder in the form of single particles and clusters composed of 2 to 5 and 6 to 60 single particles. The mass of the Y2O3 powder in the form of clusters composed of 6 to 60 single particles is 50% to 80% of the Y2O3 raw material powder. The Y₂O₃ raw material powder has a primary particle size of 20–100 nm, a primary average particle size of 30–70 nm, and a specific surface area of ​​20–30 m². 2 / g.

2. The method according to claim 1, characterized in that: The Y2O3 raw material powder can be first ball-milled in anhydrous ethanol at a speed of 150-180 rpm for 8-14 h using silicon nitride balls with a diameter of 3-5 mm, and then mixed with AlON powder. The ball-to-powder ratio of the ball-milled Y2O3 raw material powder is 8-11:

1.

3. The method according to claim 1, characterized in that: The Y2O3 raw material powder can be prepared by the following method: S1: Weigh yttrium nitrate and citric acid in a molar ratio of 1:3, add 50 mL of deionized water, and stir to dissolve until a clear solution is formed; S2: Weigh ethylene glycol according to the molar ratio of citric acid to ethylene glycol 3:1, add it to the transparent solution obtained in S1, heat it in an oil bath to 70~90℃, and stir continuously until a viscous sol is formed. S3: The viscous sol obtained in S2 is kept in an oven at 70~90℃ for 20~26 h to form a gel; S4: The gel obtained in S3 is heated to 220-250℃ in a muffle furnace at a rate of 5-30℃ / min and held for 1-4 h to foam and form a porous precursor. S5: Grind the porous precursor, pass it through a 50-mesh sieve, and heat it in a muffle furnace at 10~20℃ / min to 850~950℃ and hold it for 1~4h to obtain pure phase Y2O3 powder.

4. The method according to claim 3, characterized in that: The purity of the yttrium nitrate is ≥99.99%, the purity of the citric acid is ≥99.5%, and the purity of the ethylene glycol is ≥99%.

5. The method according to claim 1, characterized in that: The Y₂O₃ raw material powder and AlON raw material powder are first ball-milled at 150-180 rpm for 12-14 h, and then ball-milled again at 180-240 rpm for 16-20 h to obtain an AlON / Y₂O₃ mixed powder. The D of the obtained mixed powder is... 50 The particle size ranges from 0.8 to 1.4 μm, and the particle size distribution ranges from 0.05 to 8.0 μm. The amount of Y2O3 raw material powder is 0.2 to 0.4% of the mass of AlON raw material powder.

6. The method according to claim 1, characterized in that: The unidirectional pressure preforming is completed at 30~60 MPa, and the cold isostatic pressing is completed at 100~180 MPa.

7. The method according to claim 1, characterized in that: The pressureless sintering process involves a heating rate of 10~30℃ / min, a sintering temperature of 1860~1900℃, and a holding time of 3.5~5.5 h.

8. The method according to claim 1, characterized in that: The method includes a post-processing step: grinding and polishing the AlON transparent ceramic prepared by rapid pressureless sintering.

9. The AlON transparent ceramic prepared by the method of claim 1, characterized in that: The transmittance is ≥80% in the 350~4480 nm band, with a maximum transmittance of 87.5%, and a transmittance of 81.2% at 400 nm. HV>17 GPa.

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