A method for low temperature sintering of yttria ceramics

Abstract

The present application relates to the technical field of ceramic preparation, and discloses a low-temperature sintering method for yttrium oxide ceramics, which comprises the following steps: mixing yttrium oxide powder with halide complex phase additives containing anhydrous yttrium chloride and anhydrous yttrium fluoride, and pressing the mixture into a green body; first, heating in a dry inert atmosphere to make the additives melt and wet the particles; then, introducing water vapor and controlling the partial pressure, using the priority hydrolysis of yttrium chloride to build a porous framework, and maintaining the communication of exhaust channels; finally, increasing the temperature and the water vapor partial pressure to drive the hydrolysis of yttrium fluoride and complete the densification. The present application uses the step-by-step hydrolysis characteristics of the additives to realize the ordered transition from liquid phase filling to solid phase framework support, and solves the problems of premature closure of exhaust channels and deformation of the green body due to bubbling during low-temperature sintering. The prepared yttrium oxide ceramics have fine grains, high density and no grain boundary impurities, and have excellent mechanical properties and corrosion resistance.

Description

Technical Field

[0001] This invention relates to the field of ceramic preparation technology, specifically to a low-temperature sintering method for yttrium oxide ceramics. Background Technology

[0002] Yttrium oxide ceramics, due to their resistance to plasma erosion, chemical stability, and optical properties, are used in semiconductor etching equipment components, infrared optical windows, and laser substrates. However, because yttrium oxide has a high melting point and low sintering reactivity in pure powder form, high sintering temperatures are required to achieve densification. High-temperature sintering not only increases energy consumption but also easily leads to grain coarsening, thereby reducing the material's mechanical strength and thermal shock resistance.

[0003] To lower the sintering temperature, existing technologies introduce sintering aids such as lithium fluoride, alumina, or silicon dioxide to promote densification through a liquid-phase sintering mechanism. However, these aids remain at the grain boundaries as amorphous or second-phase phases, reducing the grain boundary bonding and material transmittance. Furthermore, they readily react in corrosive environments, thus reducing the service life of yttrium oxide components.

[0004] Low-temperature sintering using halide additives is another approach, but this route faces the challenge of competing between degassing and densification. While the formation of a liquid phase by halide additives at low temperatures can accelerate shrinkage, the premature sealing of the surface pores by the liquid phase can hinder the escape of internal reactive gases. When the gas generation rate exceeds the evacuation rate, closed pores will form inside the ceramic, leading to blistering, deformation, or insufficient density in the sintered body. Existing sintering processes struggle to simultaneously address the challenges of maintaining degassing channels and eliminating porosity during low-temperature densification, making it impossible to produce yttrium oxide ceramics that combine high density, fine grain structure, and high purity. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a low-temperature sintering method for yttrium oxide ceramics, which solves the technical problems of existing yttrium oxide ceramic sintering technologies being unable to achieve both high density and high purity at low temperatures, and being prone to bubbling and deformation of the green body due to premature closure of the exhaust channels.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention provides a low-temperature sintering method for yttrium oxide ceramics. This method utilizes the difference in hydrolysis characteristics between yttrium chloride and yttrium fluoride, and sequentially completes liquid phase wetting, framework construction, and densification and impurity removal by controlling the temperature and water vapor partial pressure in stages.

[0008] The method includes: mixing yttrium oxide powder with a halide multiphase additive and pressing it into shape, wherein the halide multiphase additive comprises anhydrous yttrium chloride and anhydrous yttrium fluoride.

[0009] The sintering process employs a segmented temperature and atmosphere control strategy:

[0010] First, the green blank is heated to the first temperature range of 750℃~800℃ under a dry and inert atmosphere and held at this temperature. During this stage, a low eutectic liquid phase formed by anhydrous yttrium chloride and anhydrous yttrium fluoride is used to wet the surface of yttrium oxide particles and fill the interparticle gaps without hydrolysis, thereby promoting particle rearrangement and increasing the density of the green blank.

[0011] Subsequently, the temperature is raised to a second temperature range of 820℃ to 880℃, while a controlled first water vapor partial pressure of 2.0 kPa to 5.0 kPa is introduced. During this stage, taking advantage of the higher hydrolysis rate of anhydrous yttrium chloride compared to anhydrous yttrium fluoride, the chloride component in the liquid phase is preferentially hydrolyzed into a solid product. This solid product forms a porous support framework within the green body, thereby delaying the closure of the sintering neck, maintaining unobstructed gas transport channels, and preventing the formation of closed pores.

[0012] Finally, the temperature is raised to a third temperature range of 950℃ to 1100℃, and the partial pressure of water vapor is adjusted to a second water vapor pressure of 10 kPa to 25 kPa. Under these conditions, the remaining anhydrous yttrium fluoride component undergoes a hydrolysis reaction, while the dissolution and precipitation mechanism at the liquid-solid interface promotes mass transfer, completing the densification process. The hydrogen halide gas generated during the hydrolysis reaction is discharged through unsealed pore channels, achieving the removal of sintering aids and the self-purification of the matrix.

[0013] In a preferred embodiment, the molar ratio of anhydrous yttrium chloride to anhydrous yttrium fluoride in the halide multiphase additive is controlled between 2:1 and 4:1. At this ratio, the higher chlorine content provides sufficient liquid phase at low temperatures to ensure wetting and forms a adequate supporting framework in the intermediate temperature range; the appropriate fluorine content maintains mass transfer capacity at high temperatures, preventing excessive grain growth.

[0014] Furthermore, to ensure the uniformity of the additive distribution and its reactivity, the halide multiphase additive is preferably prepared by wet ball milling with an anhydrous organic solvent in an inert environment with extremely low water and oxygen content, and then sealed and stored after drying to remove the solvent. This pretreatment prevents the additive from absorbing moisture and hydrolyzing before sintering, ensuring the controllability of the hydrolysis reaction at each stage.

[0015] In this method, the amount of halide multiphase additive added is preferably 10.0% to 15.0% of the total mass of the mixed powder, and the molding pressure is preferably 200 MPa to 350 MPa. Appropriate addition balances the liquid phase filling efficiency with the final residual amount, while the molding pressure ensures the initial packing density of the green body and reduces the probability of deformation during sintering shrinkage.

[0016] Regarding process parameters, the heating rate and holding time are set according to the reaction kinetics characteristics of each stage. The first stage uses relatively rapid heating combined with short holding time to reduce volatilization; the second stage uses a slower heating rate and a longer holding time to match the hydrolysis rate of chloride and prevent the destruction of the skeleton structure due to excessively fast reaction rate; the high temperature and long holding time in the third stage ensures sufficient densification and complete removal of anionic impurities.

[0017] This invention provides a low-temperature sintering method for yttrium oxide ceramics. It has the following beneficial effects:

[0018] 1. This invention solves the problem of premature closure of the exhaust channel during sintering by controlling the stepwise hydrolysis reaction of anhydrous yttrium chloride and anhydrous yttrium fluoride. The solid products generated by the preferential hydrolysis of yttrium chloride are used to construct a supporting framework, maintaining the connectivity of the internal pore channels of the sintered body. This prevents gas obstruction, bubbling, or deformation of the green body caused by excessive liquid phase or excessively rapid surface closure, thus ensuring the structural integrity of the sintered body.

[0019] 2. The halide multiphase additive used in this invention can achieve complete conversion into the matrix material. Under a sintering atmosphere containing water vapor, yttrium ions in the additive are converted into yttrium oxide matrix, while anions escape in gaseous form, avoiding the impurity phase or glassy phase formed by the residue at the grain boundaries of traditional non-volatile additives, thus improving the chemical purity and grain boundary bonding of the material.

[0020] 3. This invention achieves low-temperature densification of yttrium oxide ceramics, suppressing excessive grain growth. Compared to traditional high-temperature sintering processes, the ceramics prepared by this method have a fine and uniform microstructure. This fine-grained structure enables the material to exhibit excellent mechanical properties and good acid corrosion resistance. Attached Figure Description

[0021] Figure 1 The figures are comparison charts of relative density and residual impurities of the present invention, wherein (a) is a comparison chart of relative density of yttrium oxide ceramics in each experimental group; and (b) is a comparison chart of total amount of residual halogen impurities in each experimental group.

[0022] Figure 2 This is a comparison chart showing the relationship between grain size and mechanical properties of samples under different processes according to the present invention. Detailed Implementation

[0023] Preparation Examples 1-3:

[0024] Preparation Example 1:

[0025] This preparation example provides a halide multiphase additive for low-temperature sintering of yttrium oxide ceramics, wherein the molar ratio of yttrium chloride to yttrium fluoride is 2:1. The specific preparation steps are as follows:

[0026] In an inert atmosphere glove box with both water and oxygen content below 0.1 ppm, 39.05 g of anhydrous yttrium chloride powder and 14.59 g of anhydrous yttrium fluoride powder were accurately weighed. The weighed powders were placed in a clean polytetrafluoroethylene ball mill jar, 200 mL of anhydrous ethanol was added as a dispersion medium, and 500 g of high-purity zirconia grinding balls were added. The ball mill jar was sealed and removed from the glove box, and placed on a planetary ball mill. The mixture was ball milled at 300 r / min for 6 hours. After ball milling, the slurry was rotary dried at 70 °C to constant weight under a dry nitrogen flow. The obtained powder was passed through a 200-mesh nylon sieve and immediately transferred to a vacuum aluminum-plastic bag for sealed storage to obtain halide multiphase additive A.

[0027] Preparation Example 2:

[0028] This preparation example provides a halide multiphase additive for low-temperature sintering of yttrium oxide ceramics, wherein the molar ratio of yttrium chloride to yttrium fluoride is 3:1. The specific preparation steps are as follows:

[0029] The operating environment and ball milling process parameters were kept the same as in Preparation Example 1. The only difference was the amount of raw materials weighed. 58.58 g of anhydrous yttrium chloride powder and 14.59 g of anhydrous yttrium fluoride powder were accurately weighed. The mixture, drying and sieving processes were carried out in the same manner as in Preparation Example 1, and the halide multiphase additive B was finally obtained and stored in a sealed container.

[0030] Preparation Example 3:

[0031] This preparation example provides a halide multiphase additive for low-temperature sintering of yttrium oxide ceramics, wherein the molar ratio of yttrium chloride to yttrium fluoride is 4:1. The specific preparation steps are as follows:

[0032] The operating environment and ball milling process parameters were kept the same as in Preparation Example 1. The only difference was the amount of raw materials weighed. 78.10 g of anhydrous yttrium chloride powder and 14.59 g of anhydrous yttrium fluoride powder were accurately weighed. The mixture, drying and sieving processes were carried out in the same manner as in Preparation Example 1, and the halide multiphase additive C was finally obtained and stored in a sealed container.

[0033] Examples 1-6:

[0034] Example 1:

[0035] This embodiment provides a low-temperature sintering method for yttrium oxide ceramics, including the following steps:

[0036] (1) Preparation of green body: In a glove box, weigh 88.0g of high-purity yttrium oxide powder and 12.0g of halide multiphase additive B obtained in Preparation Example 2 (chlorofluorine molar ratio 3:1, additive addition amount accounts for 12.0% of the total mass of mixed powder); place the mixed powder in a ball mill jar containing anhydrous ethanol and ball mill for 4 hours, dry and sieve, and then mold and press at 15MPa and cold isostatic pressing at 200MPa to obtain a round green body with a relative density of about 55%;

[0037] (2) Liquid phase wetting: Place the green blank in a tube furnace, introduce high-purity argon gas with a flow rate of 300 sccm, heat it to 780°C at a rate of 8°C / min, and keep it at this temperature for 45 minutes to allow the additives to fully melt and wet the yttrium oxide particles.

[0038] (3) Framework construction: The temperature is increased to 850℃ at a rate of 3℃ / min, and the atmosphere is switched to humid argon carrying water vapor. The water vapor partial pressure in the furnace is controlled to be 3.5kPa. Under these conditions, the process is maintained for 90 minutes, and a porous framework is constructed by preferential hydrolysis of chloride.

[0039] (4) Densification and self-purification: The temperature is increased to 1000℃ at a rate of 4℃ / min, while the water vapor partial pressure is adjusted to 15kPa. Under these conditions, the temperature is maintained for 3 hours to drive the hydrolysis of fluoride and complete densification.

[0040] (5) Cooling: Cut off the water vapor, purge with dry argon gas for 30 minutes, and then let the furnace cool naturally to room temperature.

[0041] Example 2:

[0042] This embodiment provides a low-temperature sintering method for yttrium oxide ceramics, including the following steps:

[0043] (1) Preparation of green body: In a glove box, weigh 90.0g of high-purity yttrium oxide powder and 10.0g of halide multiphase additive B obtained in Preparation Example 2 (the amount of additive added accounts for 10.0% of the total mass of the mixed powder); ball mill, dry and shape according to the same process as in Example 1 to obtain green body;

[0044] (2) Liquid phase wetting: Place the green blank in a tube furnace, introduce high-purity argon gas with a flow rate of 200 sccm, heat it to 750°C at a rate of 5°C / min, and hold it at this temperature for 60 minutes;

[0045] (3) Skeleton construction: The temperature is slowly increased to 820℃ at a rate of 2℃ / min, while the atmosphere is switched to introduce water vapor and the water vapor partial pressure in the furnace is controlled to be 2.0kPa. Under these conditions, it is maintained for 120 minutes.

[0046] (4) Densification and self-purification: The temperature was increased to 950℃ at a rate of 3℃ / min, the water vapor partial pressure was adjusted to 10kPa, and the temperature was maintained for 4 hours.

[0047] (5) Cooling: Cut off the water vapor, purge with dry argon gas and then cool with the furnace.

[0048] Example 3:

[0049] This embodiment provides a low-temperature sintering method for yttrium oxide ceramics, including the following steps:

[0050] (1) Preparation of green body: In a glove box, weigh 85.0g of high-purity yttrium oxide powder and 15.0g of halide multiphase additive B obtained in Preparation Example 2 (the amount of additive added accounts for 15.0% of the total mass of the mixed powder); ball mill, dry and shape according to the same process as in Example 1 to obtain green body;

[0051] (2) Liquid phase wetting: Place the green blank in a tube furnace, introduce high-purity nitrogen gas with a flow rate of 500 sccm, heat it to 800℃ at a rate of 10℃ / min, and keep it at this temperature for 30 minutes.

[0052] (3) Skeleton construction: The temperature is increased to 880℃ at a rate of 5℃ / min, while the atmosphere is switched to introduce water vapor and the water vapor partial pressure in the furnace is controlled to be 5.0kPa. Under these conditions, it is maintained for 60 minutes.

[0053] (4) Densification and self-purification: The temperature was increased to 1100℃ at a rate of 5℃ / min, the water vapor partial pressure was adjusted to 25kPa, and the temperature was maintained for 2 hours.

[0054] (5) Cooling: Cut off the water vapor, purge with dry nitrogen and then cool with the furnace.

[0055] Example 4:

[0056] This embodiment provides a low-temperature sintering method for yttrium oxide ceramics, including the following steps:

[0057] (1) Preparation of green body: In a glove box, weigh 88.0g of high-purity yttrium oxide powder and 12.0g of halide multiphase additive A obtained in Preparation Example 1 (chlorofluorine molar ratio 2:1, additive addition amount accounts for 12.0% of the total mass of mixed powder); the remaining mixing and molding steps are completely consistent with those in Example 1;

[0058] (2) Sintering process: The heating program, holding time and atmosphere control parameters in steps (2) to (5) are consistent with those in Example 1.

[0059] Example 5:

[0060] This embodiment provides a low-temperature sintering method for yttrium oxide ceramics, including the following steps:

[0061] (1) Preparation of green body: In a glove box, weigh 88.0g of high-purity yttrium oxide powder and 12.0g of halide multiphase additive C obtained in Preparation Example 3 (chlorofluorine molar ratio 4:1, additive addition amount accounts for 12.0% of the total mass of mixed powder); the remaining mixing and molding steps are completely consistent with those in Example 1;

[0062] (2) Sintering process: The heating program, holding time and atmosphere control parameters in steps (2) to (5) are consistent with those in Example 1.

[0063] Example 6:

[0064] This embodiment provides a low-temperature sintering method for yttrium oxide ceramics, including the following steps:

[0065] (1) Preparation of green body: In a glove box, weigh 90.0g of high-purity yttrium oxide powder and 10.0g of halide multiphase additive C obtained in Preparation Example 3 (chlorofluorine molar ratio 4:1, additive addition amount accounts for 10.0% of the total mass of mixed powder); the remaining mixing and molding steps are completely consistent with those in Example 1;

[0066] (2) Sintering process: The heating program, holding time and atmosphere control parameters in steps (2) to (5) are consistent with those in Example 1.

[0067] Comparative Examples 1-6:

[0068] Comparative Example 1: The difference from Example 1 is that the auxiliary component is only anhydrous yttrium chloride (…). It does not contain anhydrous yttrium fluoride, and the total amount of additives remains at 12.0g. All other formulations and process parameters are the same.

[0069] Comparative Example 2: The difference from Example 1 is that the auxiliary component is only anhydrous yttrium fluoride (… It does not contain anhydrous yttrium chloride, and the total amount of additives remains at 12.0g. All other formulations and process parameters are the same.

[0070] Comparative Example 3: Compared with Example 1, the difference is that the inert atmosphere heat preservation of the "liquid phase wetting" stage in step (2) was omitted in the sintering process, and the operation of step (3) was carried out directly in an atmosphere containing water vapor at a temperature of 8℃ / min to 850℃. The rest are the same.

[0071] Comparative Example 4: Compared with Example 1, the difference is that the low temperature and low humidity heat preservation of the "skeleton construction" stage in step (3) is omitted in the sintering process. After step (2) is completed, the temperature is directly and rapidly raised to 1000℃ and the water vapor partial pressure is increased to carry out the operation of step (4). The rest are the same.

[0072] Comparative Example 5: Compared with Example 1, the difference is that the additive was replaced with an equal mass of the traditional sintering aid lithium fluoride (LiF), while the rest of the formulation and process parameters were the same.

[0073] Comparative Example 6: Compared with Example 1, the difference is that the molar ratio of yttrium chloride to yttrium fluoride in the additives is adjusted to 1:3 (i.e., a fluorine-rich system, which is beyond the scope of the invention), while the rest of the formulation and process parameters are the same.

[0074] Test Example 1-2:

[0075] Test Example 1:

[0076] Experimental steps:

[0077] Yttrium oxide ceramic samples prepared in Examples 1 to 6 and Comparative Examples 1 to 6 were selected for performance characterization. First, according to ASTM C373, the bulk density, relative density, and apparent porosity of each group of samples were determined using the Archimedes water displacement method. The test medium was deionized water at 25°C, and the relative density was calculated based on the theoretical density of yttrium oxide, 5.01 g / cm³. 3 Secondly, the residual chloride and fluoride ion contents inside the sintered body were determined using high-temperature combustion hydrolysis-ion chromatography. After grinding and sieving, the sample was burned in an oxygen-enriched environment at 1100℃, and the absorption liquid was sent to an ion chromatograph for analysis. Finally, the appearance integrity, color, and presence of surface defects such as blistering, cracks, or powdering of the sintered body were visually observed under natural light.

[0078] Test results:

[0079] The test data for each group of samples are summarized in Table 1.

[0080] Table 1: Physical properties and residual impurity analysis data of yttrium oxide ceramics under different process conditions

[0081]

[0082] (Note: N / A indicates that the element was not added or was below the detection limit)

[0083] Test conclusion:

[0084] Combined with appendix Figure 1The data in Table 1 show that the relative densities of the samples prepared in Examples 1 to 6 all exceeded 97.5%, and the total residual halogen was controlled at a low level. Among them, the total residual amount in Example 1 was less than 50 ppm, showing the best self-purification effect. This indicates that the halide additives were converted into oxides through hydrolysis and discharged with the carrier gas, achieving densification and self-purification of the material. The comparative experimental results show that the single-component additives (Comparative Examples 1 and 2) could not balance the liquid phase wetting and reaction conversion rate, resulting in densification failure or excessive residual amount, especially the highest halogen residue in Comparative Example 2. In the process comparison, Comparative Example 3 omitted the inert atmosphere wetting step, resulting in solid hydrolysis and crust formation of the additive, blocking the liquid phase flow; Comparative Example 4 omitted the low temperature and low humidity skeleton construction step, and direct high temperature hydrolysis caused the internal gas generation rate to be greater than the diffusion rate, forming closed pores and macroscopic bubbling. Comparative Example 6 used a fluorine-rich formulation, but due to the lack of sufficient easily hydrolyzable components to build a supporting skeleton, it resulted in uneven shrinkage. Experimental results confirm that by regulating the stepwise hydrolysis kinetics of chlorides and fluorides, an orderly transition from liquid-phase filling to solid-phase framework support can be achieved, ensuring the smooth flow of gas channels during low-temperature rapid sintering.

[0085] Test Example 2:

[0086] Experimental steps:

[0087] Ceramic samples prepared in Examples 1 to 6 and Comparative Examples 2 and 5 were processed into standard test strips of 3mm × 4mm × 36mm. According to GB / T6569 standard, a three-point bending test was performed using an electronic universal testing machine with a span of 30mm and a loading rate of 0.5mm / min. The maximum fracture load was recorded, and the bending strength was calculated. The average value of 10 samples in each group was taken. The cross-sections of the tested samples were polished and hot-etched. The microstructure was observed using a scanning electron microscope, and the average grain size was statistically analyzed using the linear intercept method. Furthermore, the weighed samples were immersed in a 5% nitric acid solution at 60℃ for 24 hours for etching. After cleaning and drying, they were weighed again, and the mass loss per unit surface area was calculated to evaluate corrosion resistance.

[0088] Test results:

[0089] The specific data obtained from the experiment are shown in Table 2.

[0090] Table 2: Summary of Grain Size and Mechanical Properties of Yttrium Oxide Ceramics under Different Sintering Processes

[0091]

[0092] Test conclusion:

[0093] Combined with appendix Figure 2As shown in Table 2, the average grain size of samples from Examples 1 to 6 was controlled below 1.2 μm, and the flexural strength generally exceeded 200 MPa. Overall, they exhibited the advantageous characteristics of this invention, combining fine grains (<1.2 μm) with high strength, consistent with the principle of fine grain strengthening. In contrast, although Comparative Example 5 with added LiF additive had a higher density, it showed significant grain coarsening, leading to a decrease in strength. Regarding corrosion resistance, the mass loss of the example samples was significantly lower than that of the comparative examples; Example 1 showed a loss of only 0.08 mg / cm³. 2 Comparative Example 2, however, suffered from insufficient strength due to incomplete densification and severe corrosion due to residual yttrium fluoride. Comparative Example 5 exhibited poor corrosion resistance due to the enrichment of lithium impurities at grain boundaries. The additive ratio had a fine-tuning effect on performance; the low fluoride ratio (Example 2) resulted in the smallest grains, but the reduced liquid phase led to greater strength dispersion. The high fluoride ratio (Example 3) provided sufficient liquid phase, thoroughly eliminated porosity, and achieved a balance between strength and corrosion resistance. In summary, the halide-differential hydrolysis strategy employed in this invention achieves low-temperature densification while inhibiting excessive grain growth and reducing grain boundary impurities, resulting in yttrium oxide ceramics that possess both high strength and excellent chemical corrosion resistance.

Claims

1. A low-temperature sintering method for yttrium oxide ceramics, characterized in that, Includes the following steps: Yttrium oxide powder is mixed evenly with a halide multiphase additive to obtain a mixed powder, and the mixed powder is pressed into a blank to obtain a green body; the halide multiphase additive includes anhydrous yttrium chloride and anhydrous yttrium fluoride; Under a dry, inert atmosphere, the temperature is raised from room temperature to a target temperature within a first temperature range of 750°C to 800°C and held at that temperature, so that the halide multiphase additive melts and wets the yttrium oxide powder particles, forming a liquid-wetted green body. The liquid-wetted green body is then heated to a target temperature within the second temperature range of 820°C to 880°C. During this heating process or the subsequent holding stage, water vapor is introduced and the first water vapor partial pressure is controlled to be 2.0 kPa to 5.0 kPa. The green body is then held at this temperature and pressure, and a porous framework is constructed by preferential hydrolysis of the anhydrous yttrium chloride. After the porous framework is constructed, the temperature is raised to the target temperature in the third temperature range of 950℃ to 1100℃, and the partial pressure of water vapor is adjusted to the second water vapor partial pressure of 10kPa to 25kPa. The temperature and partial pressure are maintained at this temperature to drive the hydrolysis of the anhydrous yttrium fluoride and complete the densification.

2. The low-temperature sintering method for yttrium oxide ceramics according to claim 1, characterized in that, In the halide complex additive, the molar ratio of anhydrous yttrium chloride to anhydrous yttrium fluoride is 2:1 to 4:

1.

3. The low-temperature sintering method for yttrium oxide ceramics according to claim 2, characterized in that, The halide multiphase additive is prepared in advance by the following method: Under an inert atmosphere with water and oxygen content below 0.1 ppm, anhydrous yttrium chloride powder and anhydrous yttrium fluoride powder were weighed, and the molar ratio of the anhydrous yttrium chloride to the anhydrous yttrium fluoride was controlled to be 2:1 to 4:

1. The anhydrous yttrium chloride powder and the anhydrous yttrium fluoride powder were placed in an anhydrous organic solvent and ball-milled and mixed using zirconia grinding balls to obtain a slurry. The anhydrous organic solvent was removed under a dry, inert gas flow and dried to constant weight. After sieving, the product was sealed and stored.

4. The low-temperature sintering method for yttrium oxide ceramics according to claim 1, characterized in that, The amount of the halide complex additive added accounts for 10.0% to 15.0% of the total mass of the mixed powder; the pressing molding includes compression molding and cold isostatic pressing, wherein the pressure of the cold isostatic pressing is 200 MPa to 350 MPa.

5. The low-temperature sintering method for yttrium oxide ceramics according to claim 1, characterized in that, The dry, inert atmosphere is argon or nitrogen; the holding time in the first temperature range is 30 to 60 minutes.

6. The low-temperature sintering method for yttrium oxide ceramics according to claim 1, characterized in that, The time spent in the second temperature range is 60 to 120 minutes.

7. The low-temperature sintering method for yttrium oxide ceramics according to claim 1, characterized in that, The time spent in the third temperature range is 2 to 4 hours.

8. The low-temperature sintering method for yttrium oxide ceramics according to claim 1, characterized in that, The rate at which the blank is heated from room temperature to the first temperature range is 5–10 °C / min; the rate at which it is heated from the first temperature range to the second temperature range is 2–5 °C / min; and the rate at which it is heated from the second temperature range to the third temperature range is 3–5 °C / min.

9. The low-temperature sintering method for yttrium oxide ceramics according to claim 1, characterized in that, It also includes a cooling step: after densification is completed, the supply of water vapor is cut off, dry inert gas is introduced to purge the furnace, and then the furnace is cooled to room temperature.

10. The low-temperature sintering method for yttrium oxide ceramics according to claim 3, characterized in that, The anhydrous organic solvent is anhydrous ethanol; the ball milling mixing time is 4 to 8 hours; and the drying temperature is 60 to 80°C.

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