Wide-temperature-range gamma-Y2Si2O7 material and preparation method thereof

Abstract

The invention belongs to the field of high-temperature-resistant ceramic materials, and discloses a wide-temperature-range gamma-Y2Si2O7 material and a preparation method thereof. The preparation method comprises the following steps: heating and stirring Y2O3 sol and an ethanol solution containing Yb < 3 + > and Er < 3 + > to obtain a transparent solution, then heating and stirring the transparent solution and SiO2 sol under the condition of polyethylene glycol to obtain mixed sol, heating in a sealed pressure container, and then drying and calcining to obtain the composite material. According to the preparation method disclosed by the invention, the gamma-Y2Si2O7 is subjected to atomic-scale solid solution by using the same-family rare earth elements with different ion radiuses, so that the calcination temperature is reduced, the defects of high gamma phase generation temperature and low stable temperature in the Y2Si2O7 are effectively overcome, the prepared gamma-Y2Si2O7 has a wider stable existence temperature range, and the use temperature range of the gamma-Y2Si2O7 is greatly expanded.

Description

Technical Field

[0001] This invention relates to the field of high-temperature resistant ceramic materials technology, and in particular to a wide-temperature-range γ-Y2Si2O7 material and its preparation method. Background Technology

[0002] Y₂Si₂O₇, as an excellent high-temperature functional and structural material, possesses numerous advantages such as high temperature resistance, corrosion resistance, low thermal expansion, and oxidation resistance, making it widely used as a high-temperature thermal barrier coating and environmental barrier coating. However, with increasing temperature, Y₂Si₂O₇ gradually undergoes interconversions between α, β, γ, and δ crystal structures. Among these, the γ-phase structure of Y₂Si₂O₇ exhibits the most outstanding physicochemical properties. However, current research and applications face the challenge that the formation temperature of γ-Y₂Si₂O₇ needs to reach above 1400℃, while above 1535℃ it rapidly transforms into the metastable δ-Y₂Si₂O₇. Therefore, its high formation temperature and low stable existence temperature result in a narrow application temperature range for γ-Y₂Si₂O₇, significantly limiting its application scope in the high-temperature aerospace field.

[0003] Therefore, there is an urgent need to find a method and materials that can reduce the formation temperature of γ-Y2Si2O7 while significantly increasing the phase transition temperature of γ-Y2Si2O7 to δ-Y2Si2O7. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above and provide a γ-Y2Si2O7 material with wide temperature range stability.

[0005] To address the aforementioned technical problems, this invention, based on the characteristics, current research status, and existing issues of γ-Y₂Si₂O₇ ceramics, and leveraging the advantage of effective solid solution between rare earth ions of different radii within the same group, provides Yb 3+ and Er 3+ Simultaneously, a novel material system of highly stable γ-Y2Si2O7 material was formed by solid solution with Y2Si2O7, and a preparation method capable of obtaining a wide stable temperature range was also developed.

[0006] Based on this, the technical solution proposed by the present invention is as follows: A method for preparing a γ-Y2Si2O7 material with a wide temperature range includes the following steps: (1) Dilute the nano-sized Y2O3 sol with water and heat and stir in a closed environment to add Yb 3+ and Er 3+ An ethanol solution was added to the diluted Y2O3 sol, and the mixture was heated and stirred in a sealed environment until it became transparent, thus obtaining Y2O3-Yb2O3-Er2O3 sol. (2) After diluting the nano-sized SiO2 sol with anhydrous ethanol, add it to the Y2O3-Yb2O3-Er2O3 sol in step (1) to obtain a mixed solution, then add polyethylene glycol to form a new solution, heat and stir to obtain Y2O3-Yb2O3-Er2O3-SiO2 sol; (3) The Y2O3-Yb2O3-Er2O3-SiO2 sol is heated and kept warm in a sealed pressure vessel to obtain a wet gel, and then dried to obtain a dry Y2O3-Yb2O3-Er2O3-SiO2 gel. (4) The Y2O3-Yb2O3-Er2O3-SiO2 dry gel is calcined to obtain the wide-temperature-range γ-Y2Si2O7 material.

[0007] In terms of preparation method, a stable Y₂O₃-Yb₂O₃-Er₂O₃-SiO₂ sol was first obtained. This sol has a nanoscale particle size, thus exhibiting high reactivity. It can complete the full reaction between rare earth oxides Y₂O₃, Yb₂O₃, Er₂O₃ and SiO₂ at a very low temperature, with the reaction temperature for the formation of rare earth disilicates being 1300℃. Compared with the traditional solid-state sintering reaction of micron-sized rare earth oxides with silicon dioxide, the reaction temperature of this sol is reduced by nearly 300℃. Furthermore, starting from a liquid-phase sol allows for better uniform solid solution of Y₂O₃-Yb₂O₃-Er₂O₃-SiO₂ at the nanoscale, enabling the material system to achieve compositional homogeneity at a more microscopic level.

[0008] Furthermore, this invention, taking into account the characteristics of the sol itself, employs solvothermal confined curing technology to effectively avoid sol instability caused by solvent reduction during ordinary drying and curing processes. Such sol instability leads to the initial instability and segregation of one phase in the Y2O3-Yb2O3-Er2O3-SiO2 sol during curing, significantly resulting in uneven component distribution and consequently, gel component inhomogeneity, ultimately preventing the acquisition of wide-temperature-range stable γ-Y2Si2O7. Therefore, this invention, utilizing solvothermal confined curing technology, is more conducive to obtaining component-uniform, wide-temperature-range γ-Y2Si2O7.

[0009] In the above preparation method, preferably, in step (1), the solid content of the Y2O3 sol is 20wt%~40wt%, the pH value is 7.5~10.5, and the particle size is 4~10nm; in the process of diluting the Y2O3 sol with water, the mass ratio of Y2O3 sol to water is 1:1~4, the temperature of closed heating and stirring is 60~90℃, the stirring speed is 420-540r / min, and the stirring time is 4~10h.

[0010] Preferably, in step (1), the Yb-containing 3+ and Er 3+ The ethanol solution is obtained by adding Yb(NO3)3 and Er(NO3)3 to anhydrous ethanol and mixing and stirring until dissolved, wherein the atomic molar ratio of Yb to Er is 1:1; the mass ratio of Yb(NO3)3 and Er(NO3)3 to ethanol is 1:5~10, and the stirring time is 5~10h; the temperature for continued heating and stirring until transparent is 80~120℃, the rotation speed is 480~600r / min, and the oil bath time is 4~10h; in the Y2O3-Yb2O3-Er2O3 sol, the atomic molar ratio of (Yb+Er):Y is 3:3~7.

[0011] Preferably, in step (2), the solid content of the SiO2 sol is 15%~40wt%, the particle size is 10~60nm, the pH value is 7.5~9, and the mass ratio of SiO2 sol to anhydrous ethanol is 1:1~4 during the process of stirring and diluting the SiO2 sol with anhydrous ethanol.

[0012] Preferably, in step (2), the mixing ratio of the diluted SiO2 sol to the Y2O3-Yb2O3-Er2O3 sol satisfies the ratio of Si atoms to Y atoms. 3+ +Yb 3+ +Er 3+ The molar ratio between them is 1:1; the relative molecular mass of the polyethylene glycol is 200~600, and the mass ratio of the polyethylene glycol to the mixed solution is 2~5:10.

[0013] Preferably, in step (2), the heating and stirring method is to first heat and stir in a closed manner for 2 to 4 hours, and then heat and stir in an open manner for 4 to 8 hours. The heating temperature is 60 to 90°C, and the stirring speed is 450 to 540 r / min.

[0014] Preferably, in step (3), the internal solution loading of the sealed pressure vessel is 1 / 2 to 2 / 3 of the total volume, the heating temperature after sealing the pressure vessel is 140 to 180°C, and the holding time is 2 to 6 hours; the drying temperature regime is as follows: holding at 80°C for 2 hours, at 100°C for 2 hours, at 120°C for 2 hours, at 150°C for 1 hour, and at 200°C for 1 hour.

[0015] Preferably, in step (4), the calcination temperature is 1200~1500℃ and the calcination time is 1~6h.

[0016] This invention proposes a method for obtaining an ultra-fine, uniform γ-Y₂Si₂O₇ material with a wide temperature range by combining rare-earth ion doping modification with sol-gel and solvothermal techniques, along with its preparation method. By introducing rare-earth ions of the same group, this invention effectively lowers the formation temperature of γ-Y₂Si₂O₇ without reducing the melting point of Y₂Si₂O₇ itself, while significantly increasing the phase transition temperature of γ-Y₂Si₂O₇ to δ-Y₂Si₂O₇. This greatly expands the temperature range of γ-Y₂Si₂O₇ with its excellent physical and chemical properties, providing an ideal solution to the phase transition problem in its application at high temperatures.

[0017] Based on a general inventive concept, the present invention also provides a wide-temperature-range γ-Y2Si2O7 material obtained by the above preparation method, wherein the phase transition temperature of γ-Y2Si2O7 to δ-Y2Si2O7 is above 1700℃, more preferably above 1800℃, and the γ-Y2Si2O7 material does not contain other dopants.

[0018] Preferably, the aforementioned wide-temperature-range γ-Y₂Si₂O₇ material is doped with Yb. 3+ and Er 3+ Rare earth ions, of which Yb 3+ and Er 3+ The molar ratio is 1:1, Yb 3+ and Er 3+ Total ions and Y 3+ The molar ratio of ions is 3:3~7.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention uses Yb 3+ and Er 3+ Rare earth ion doping solid solution, because it belongs to the same rare earth group elements and has the same number of outermost electrons, has better compatibility with the Y₂Si₂O₇ crystal structure during the solid solution process. This solid solution does not form a new ternary glass phase as with other alkaline earth metal or transition metal ion doping solid solutions, thus avoiding a decrease in melting point and heat resistance. In other words, the Yb of this invention... 3+ and Er 3+ Rare earth ions can improve the upper and lower limits of the stable temperature range of γ-Y2Si2O7 crystals without reducing other physicochemical properties.

[0020] (2) This invention starts from nanoscale sol, which completely avoids the problems of uneven reaction and excessively high synthesis temperature caused by starting from micron-scale rare earth oxide powder. It is more conducive to generating high-purity phase γ-Y2Si2O7 at low temperature, which greatly reduces the generation temperature of γ-Y2Si2O7. At present, the temperature of Y2Si2O7 generated by the solid-phase reaction of micron-scale rare earth oxides and silica powder in traditional technology is not lower than 1600℃, and there are a large number of incompletely reacted Y2SiO5 and SiO2. The purity of Y2Si2O7 phase is low, and the purity of γ-Y2Si2O7 phase is even lower.

[0021] (3) The present invention uses a solvothermal confined curing method to synthesize Y2Si2O7, which avoids the problem that a certain phase in the Y2O3-SiO2 sol will become unstable and precipitate first due to the large reduction of solvent during the natural drying process. At the same time, due to the increase of internal pressure during the self-pressurization process, the sol system exhibits an explosive structure, which greatly improves the reactivity and sintering activity between Y2O3 and SiO2.

[0022] (4) The gamma-phase yttrium silicate (γ-Y2Si2O7) material prepared by the present invention, compared with the traditional polycrystalline Y2Si2O7, utilizes rare earth elements of the same group with different ionic radii to perform atomic-level solid solution on it, effectively overcoming the defects of high gamma phase formation temperature and low stability temperature in Y2Si2O7, so that γ-Y2Si2O7 has a wider stable existence temperature range, greatly expanding the operating temperature range of γ-Y2Si2O7. It can not only solve the phase transformation problem of Y2Si2O7 in the thermal barrier coating of aero-engines, but also be applicable to other thermal structural components, such as thermal insulation materials. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a process flow diagram of the preparation method of the present invention.

[0025] Figure 2 The image shows the XRD pattern of the dry gel powder obtained after drying the Y2O3-Yb2O3-Er2O3-SiO2 sol in Example 3 of this invention.

[0026] Figure 3The graph shows the linear shrinkage of the dry gel powder obtained by drying the Y2O3-Yb2O3-Er2O3-SiO2 sol in Example 3 of this invention, after being pressed into blocks and heat-treated at different temperatures. Detailed Implementation

[0027] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0028] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0029] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0030] Example 1: A γ-Y₂Si₂O₇ material with wide temperature range stability according to the present invention, wherein γ-Y₂Si₂O₇ is doped with Yb 3+ and Er 3 + Rare earth ions. The preparation method of this γ-Y₂Si₂O₇ material, such as... Figure 1 As shown, the specific process steps include the following: (1) Dilution treatment of Y2O3 sol: Select Y2O3 sol with a particle size of 4nm, a solid content of 20wt% and a pH value of 8, and then add deionized water for dilution. During the dilution process, the mass ratio of Y2O3 sol to deionized water is 1:1. The temperature of the closed oil bath stirring is 60℃, the stirring speed is 450r / min, and the stirring time is 4h to obtain low concentration Y2O3 sol.

[0031] (2) Yb 3+ and Er 3+ Solution preparation: Mix Yb(NO3)3·5H2O and Er(NO3)3·6H2O with ethanol at a mass ratio of 1:5 and stir for 6 hours. A transparent Yb solution will be obtained after stirring. 3+ and Er 3+ Ethanol solution.

[0032] (3) Preparation of Y2O3-Yb2O3-Er2O3 ternary cationic sol: The Yb2O3-Yb2O3-Er2O3 ternary cationic sol prepared in step (2) is used as follows: 3+ and Er 3+Ethanol solution was gradually added to the low-concentration Y2O3 sol diluted in step (1), and the mixture was stirred in a closed oil bath at 90°C until transparent. The stirring speed was 480 r / min, and the oil bath time was 5 h, to obtain Y2O3-Yb2O3-Er2O3 sol; Yb 3+ and Er 3+ As the solution was gradually added to the diluted Y₂O₃ sol, the atomic molar ratio of Yb to Er in the total solution was 1:1, and the atomic molar ratio of (Yb+Er)∶Y was 4:6.

[0033] (4) SiO2 sol dilution treatment: Select SiO2 sol with a solid content of 25wt%, a particle size of 30nm, and a pH value of 7.5, and then dilute it with anhydrous ethanol. The mass ratio of SiO2 sol to anhydrous ethanol during the dilution process is 1:2.

[0034] (5) Preparation of Y2O3-Yb2O3-Er2O3-SiO2 sol: The SiO2 sol diluted in step (4) is gradually added to the Y2O3-Yb2O3-Er2O3 sol prepared in step three, wherein Si atoms and rare earth ions (Y 3+ +Yb 3+ +Er 3+ A mixed solution is obtained by adding polyethylene glycol (PEG) with a relative molecular mass of 400 to the mixed solution at a mass ratio of PEG to the mixed solution of 2:10. Then, the mixture is stirred in a closed oil bath at a speed of 450 r / min and a temperature of 70℃ for 3 hours. After the closed oil bath, an open oil bath is carried out at the same temperature and speed for 6 hours. After the open oil bath, a uniform and transparent Y2O3-Yb2O3-Er2O3-SiO2 sol is obtained.

[0035] (6) Curing of Y2O3-Yb2O3-Er2O3-SiO2 sol: The Y2O3-Yb2O3-Er2O3-SiO2 sol prepared in step (5) is gradually added to a pressure vessel lined with polytetrafluoroethylene. The liquid loading volume inside the pressure vessel is 2 / 3 of the total volume. The pressure vessel is sealed and kept at 160℃ for 4 hours. After the pressure vessel is kept at 160℃ and cooled, a uniform and transparent Y2O3-Yb2O3-Er2O3-SiO2 wet gel can be obtained in the pressure vessel.

[0036] (7) Drying of Y2O3-Yb2O3-Er2O3-SiO2 gel: The Y2O3-Yb2O3-Er2O3-SiO2 wet gel cured in step (6) is placed in an oven for drying. The drying temperature regime is 80℃ for 2h → 100℃ for 2h → 120℃ for 2h → 150℃ for 1h → 200℃ for 1h. After drying, Y2O3-Yb2O3-Er2O3-SiO2 dry gel can be obtained.

[0037] (8) Calcination of Y2O3-Yb2O3-Er2O3-SiO2 dry gel: The dry gel block after drying in step (7) was further placed in a muffle furnace and calcined at 1400℃ for 5h to finally obtain a wide temperature range γ-Y2Si2O7 material.

[0038] The wide-temperature-range γ-Y2Si2O7 material prepared according to the preparation method in Example 1 maintains a high-temperature non-phase-transformation temperature above 1750℃.

[0039] Example 2: A γ-Y₂Si₂O₇ material with wide temperature range stability according to the present invention, wherein γ-Y₂Si₂O₇ is doped with Yb 3+ and Er 3 + Rare earth ions. The preparation method of this γ-Y₂Si₂O₇ material, such as... Figure 1 As shown, the specific process steps include the following: (1) Dilution treatment of Y2O3 sol: Select Y2O3 sol with a particle size of 4nm, a solid content of 30wt%, and a pH value of 9, and then add deionized water for dilution. During the dilution process, the mass ratio of Y2O3 sol to deionized water is 1:2. The temperature of the closed oil bath stirring is 80℃, the stirring speed is 480r / min, and the stirring time is 6h to obtain low concentration Y2O3 sol.

[0040] (2) Yb 3+ and Er 3+ Solution preparation: Mix Yb(NO3)3·5H2O and Er(NO3)3·6H2O with ethanol at a mass ratio of 1:8 and stir for 6 hours. A transparent Yb solution will be obtained after stirring. 3+ and Er 3+ Ethanol solution.

[0041] (3) Preparation of Y2O3-Yb2O3-Er2O3 ternary cationic sol: The Yb2O3-Yb2O3-Er2O3 ternary cationic sol prepared in step (2) is used as follows: 3+ and Er 3+Ethanol solution was gradually added to the low-concentration Y2O3 sol diluted in step (1), and the mixture was stirred in a closed oil bath at 90°C until transparent. The stirring speed was 480 r / min, and the oil bath time was 5 h, to obtain Y2O3-Yb2O3-Er2O3 sol; Yb 3+ and Er 3+ As the solution was gradually added to the diluted Y₂O₃ sol, the atomic molar ratio of Yb to Er in the total solution was 1:1, and the atomic molar ratio of (Yb+Er)∶Y was 3:7.

[0042] (4) SiO2 sol dilution treatment: Select SiO2 sol with a solid content of 30wt%, a particle size of 60nm, and a pH value of 7.5, and then dilute it with anhydrous ethanol. The mass ratio of SiO2 sol to anhydrous ethanol during the dilution process is 1:3.

[0043] (5) Preparation of Y2O3-Yb2O3-Er2O3-SiO2 sol: The SiO2 sol diluted in step (4) is gradually added to the Y2O3-Yb2O3-Er2O3 sol prepared in step three, wherein Si atoms and rare earth ions (Y 3+ +Yb 3+ +Er 3+ A mixed solution is obtained by adding polyethylene glycol with a relative molecular mass of 400 to the mixed solution at a molar ratio of 1:1. Then, polyethylene glycol is added to the mixed solution at a mass ratio of 4:10 to the mixed solution. The solution is then stirred in a closed oil bath at a speed of 510 r / min and a temperature of 80℃ for 2 hours. After the closed oil bath, an open oil bath is then performed at the same temperature and speed for 8 hours. After the open oil bath, a uniform and transparent Y₂O₃-Yb₂O₃-Er₂O₃-SiO₂ sol is obtained.

[0044] (6) Curing of Y2O3-Yb2O3-Er2O3-SiO2 sol: The Y2O3-Yb2O3-Er2O3-SiO2 sol prepared in step (5) is gradually added to a pressure vessel lined with polytetrafluoroethylene. The liquid loading volume inside the pressure vessel is 1 / 2 of the total volume. The pressure vessel is sealed and kept at 180℃ for 2 hours. After the pressure vessel is kept at 180℃ and cooled, a uniform and transparent Y2O3-Yb2O3-Er2O3-SiO2 wet gel can be obtained in the pressure vessel.

[0045] (7) Drying of Y2O3-Yb2O3-Er2O3-SiO2 gel: The Y2O3-Yb2O3-Er2O3-SiO2 wet gel cured in step (6) is placed in an oven for drying. The drying temperature regime is 80℃ for 2h → 100℃ for 2h → 120℃ for 2h → 150℃ for 1h → 200℃ for 1h. After drying, Y2O3-Yb2O3-Er2O3-SiO2 dry gel can be obtained.

[0046] (8) Calcination of Y2O3-Yb2O3-Er2O3-SiO2 dry gel: The dry gel block after drying in step (7) was further placed in a muffle furnace and calcined at 1500℃ for 4 hours to finally obtain a wide temperature range γ-Y2Si2O7 material.

[0047] The wide-temperature-range γ-Y2Si2O7 material prepared according to the preparation method in Example 2 maintains a high-temperature non-phase-transformation temperature above 1700℃.

[0048] Example 3: A γ-Y₂Si₂O₇ material with wide temperature range stability according to the present invention, wherein γ-Y₂Si₂O₇ is doped with Yb 3+ and Er 3 + Rare earth ions. The preparation method of this γ-Y₂Si₂O₇ material, such as... Figure 1 As shown, the specific process steps include the following: (1) Dilution treatment of Y2O3 sol: Select Y2O3 sol with a particle size of 8nm, a solid content of 35wt% and a pH value of 10, and then add deionized water for dilution. During the dilution process, the mass ratio of Y2O3 sol to deionized water is 1:3. The temperature of the closed oil bath stirring is 90℃, the stirring speed is 540r / min, and the stirring time is 6h to obtain low concentration Y2O3 sol.

[0049] (2) Yb 3+ and Er 3+ Solution preparation: Mix Yb(NO3)3·5H2O and Er(NO3)3·6H2O with ethanol at a mass ratio of 1:10 and stir for 5 hours. A transparent Yb solution will be obtained after stirring. 3+ and Er 3+ Ethanol solution.

[0050] (3) Preparation of Y2O3-Yb2O3-Er2O3 ternary cationic sol: The Yb2O3-Yb2O3-Er2O3 ternary cationic sol prepared in step (2) is used as follows: 3+ and Er 3+Ethanol solution was gradually added to the low-concentration Y2O3 sol diluted in step (1), and the mixture was stirred in a closed oil bath at 90°C until transparent. The stirring speed was 480 r / min, and the oil bath time was 5 h, to obtain Y2O3-Yb2O3-Er2O3 sol; Yb 3+ and Er 3+ As the solution is gradually added to the diluted Y2O3 sol, the atomic molar ratio of Yb to Er in the total solution is 1:1, and the atomic molar ratio of (Yb+Er)∶Y is 1:1.

[0051] (4) SiO2 sol dilution treatment: Select SiO2 sol with a solid content of 40wt%, a particle size of 40nm, and a pH value of 7.5, and then dilute it with anhydrous ethanol. The mass ratio of SiO2 sol to anhydrous ethanol during the dilution process is 1:4.

[0052] (5) Preparation of Y2O3-Yb2O3-Er2O3-SiO2 sol: The SiO2 sol diluted in step (4) is gradually added to the Y2O3-Yb2O3-Er2O3 sol prepared in step three, wherein Si atoms and rare earth ions (Y 3+ +Yb 3+ +Er 3+ A mixed solution is obtained by adding polyethylene glycol (PEG) with a relative molecular mass of 600 to the mixed solution at a molar ratio of 1:1. Then, a closed oil bath is stirred at a speed of 510 r / min and a temperature of 80℃ for 2 hours. After the closed oil bath, an open oil bath is then conducted at the same temperature and speed for 10 hours. After the open oil bath, a uniform and transparent Y₂O₃-Yb₂O₃-Er₂O₃-SiO₂ sol is obtained.

[0053] (6) Curing of Y2O3-Yb2O3-Er2O3-SiO2 sol: The Y2O3-Yb2O3-Er2O3-SiO2 sol prepared in step (5) is gradually added to a pressure vessel lined with polytetrafluoroethylene. The liquid loading volume inside the pressure vessel is 1 / 2 of the total volume. The pressure vessel is sealed and kept at a temperature of 140℃ for 2 hours. After the pressure vessel is kept at a temperature of 140℃ and cooled, a uniform and transparent Y2O3-Yb2O3-Er2O3-SiO2 wet gel can be obtained in the pressure vessel.

[0054] (7) Drying of Y2O3-Yb2O3-Er2O3-SiO2 gel: The Y2O3-Yb2O3-Er2O3-SiO2 wet gel cured in step (6) is placed in an oven for drying. The drying temperature regime is 80℃ for 2h → 100℃ for 2h → 120℃ for 2h → 150℃ for 1h → 200℃ for 1h. After drying, Y2O3-Yb2O3-Er2O3-SiO2 dry gel can be obtained.

[0055] (8) Calcination of Y2O3-Yb2O3-Er2O3-SiO2 dry gel: The dry gel block after drying in step (7) was further placed in a muffle furnace and calcined at 1300℃ for 6 hours to finally obtain a wide temperature range γ-Y2Si2O7 material.

[0056] The γ-Y2Si2O7 material with a wide temperature range prepared according to the preparation method in Example 3 has a high temperature resistance above 1800℃ and a purity of 98.7%. No other impurity phases were observed in XRD.

[0057] XRD analysis was performed on the dry gel powder obtained after drying the Y2O3-Yb2O3-Er2O3-SiO2 sol in step (7) of Example 3: The phase composition of the gel powder (molar ratio corresponding to Y2Si2O7 crystal phase) was analyzed using a D8 Advance X-ray diffractometer. The test conditions were: CuKα rays, tube current 40mA, tube voltage 40kV, 2θ = 15~90°, and scanning speed 4° / min.

[0058] See test results Figure 2 As shown in the figure, the spectrum exhibits a "bun" peak characteristic, without any sharp rare earth ion or rare earth silicate characteristic diffraction peaks. This indicates that the Y2O3-Yb2O3-Er2O3-SiO2 dry gel powder dried at 200℃ is in a typical amorphous state. The amorphous state has high surface energy, which can promote the complete reaction of Y2O3-Yb2O3-Er2O3-SiO2 at relatively low temperatures.

[0059] The dry gel powder obtained after drying the Y2O3-Yb2O3-Er2O3-SiO2 sol in step (7) of Example 3 was subjected to XRD analysis after heat treatment at different temperatures: The dried Y₂O₃-Yb₂O₃-Er₂O₃-SiO₂ gel powder (molar ratio corresponding to Y₂Si₂O₇ crystal phase) was heat-treated at different temperatures for 1 h, and then the phase composition of the powder was analyzed using a D8 Advance X-ray diffractometer. The test conditions were: CuKα rays, tube current 40 mA, tube voltage 40 kV, 2θ = 10–80°, and scanning speed 4° / min.

[0060] See test results Figure 2 As shown in the figure, the Y2SiO5 phase is formed at 1000℃, and it is almost completely transformed into the γ-Y2Si2O7 phase at 1300℃. As the temperature further increases, the crystallinity of the γ-Y2Si2O7 phase becomes higher and higher, and it can still maintain a high intensity γ-Y2Si2O7 diffraction peak up to 1800℃. This significantly changes the traditional characteristic of γ-Y2Si2O7 transforming into δ-Y2Si2O7 above 1500℃, thus obtaining a new γ-Y2Si2O7 material with higher temperature phase stability.

[0061] The dry gel powder obtained after drying the Y2O3-Yb2O3-Er2O3-SiO2 sol in step (7) of Example 3 was pressed into blocks, and its linear shrinkage after heat treatment at different temperatures was tested: The dried Y₂O₃-Yb₂O₃-Er₂O₃-SiO₂ gel powder (molar ratio corresponding to Y₂Si₂O₇ crystal phase) was placed in a 40 mm diameter metal mold and pressed into a 40 mm diameter, 5 mm thick circular block at 100 MPa. The circular block was then placed in a heat treatment furnace and heat-treated at different temperatures for 1 hour. The change rate of diameter and thickness before and after heat treatment was measured, and the average value of 5 measurements was taken as the final result.

[0062] See test results Figure 3 As shown in the figure, after heat treatment at 1000℃ to 1600℃, the linear shrinkage gradually increases with increasing temperature in the range of 12% to 24%. Among them, the linear shrinkage increases significantly when the temperature increases from 1000℃ to 1200℃, the change is small from 1200℃ to 1400℃, and there is a significant increase from 1400℃ to 1600℃. This indicates that Y2O3-Yb2O3-Er2O3-SiO2 has good sintering activity.

[0063] In summary, the wide-temperature-range γ-Y₂Si₂O₇ material prepared using the methods described in Examples 1 to 3 exhibits both a low reaction formation temperature and higher temperature stability. Compared to traditional polycrystalline Y₂Si₂O₇, the γ-Y₂Si₂O₇ material of this invention utilizes atomic-level solid solution of rare earth elements of the same group with different ionic radii, effectively overcoming the defects of high gamma phase formation temperature and low stability temperature in Y₂Si₂O₇. This results in a wider stable existence temperature range for γ-Y₂Si₂O₇, significantly expanding its operational temperature range. The solvothermal confined curing method for synthesizing Y₂Si₂O₇ avoids the problem of a certain phase in the Y₂O₃-SiO₂ sol becoming unstable and precipitating first due to a significant reduction in solvent during natural drying, thus greatly improving the reactivity and sintering activity between Y₂O₃ and SiO₂.

Claims

1. A method for preparing a wide-temperature-range γ-Y₂Si₂O₇ material, characterized in that, Includes the following steps: (1) Dilute the nano-sized Y2O3 sol with water and heat and stir in a closed environment to add Yb 3+ and Er 3+ An ethanol solution was added to the diluted Y2O3 sol, and the mixture was heated and stirred in a sealed environment until it became transparent, thus obtaining Y2O3-Yb2O3-Er2O3 sol. (2) After diluting the nano-sized SiO2 sol with anhydrous ethanol, add it to the Y2O3-Yb2O3-Er2O3 sol in step (1) to obtain a mixed solution, then add polyethylene glycol to form a new solution, heat and stir to obtain Y2O3-Yb2O3-Er2O3-SiO2 sol; (3) The Y2O3-Yb2O3-Er2O3-SiO2 sol is heated and kept warm in a sealed pressure vessel to obtain a wet gel, and then dried to obtain a dry Y2O3-Yb2O3-Er2O3-SiO2 gel. (4) The Y2O3-Yb2O3-Er2O3-SiO2 dry gel is calcined to obtain the wide-temperature-range γ-Y2Si2O7 material.

2. The preparation method according to claim 1, characterized in that, In step (1), the solid content of the Y2O3 sol is 20wt%~40wt%, the pH value is 7.5~10.5, and the particle size is 4~10nm; in the process of diluting the Y2O3 sol with water, the mass ratio of Y2O3 sol to water is 1:1~4, the temperature of closed heating and stirring is 60~90℃, the stirring speed is 420-540r / min, and the stirring time is 4~10h.

3. The preparation method according to claim 1, characterized in that, In step (1), the Yb-containing 3+ and Er 3+ The ethanol solution is obtained by adding Yb(NO3)3 and Er(NO3)3 to anhydrous ethanol and mixing and stirring until dissolved, wherein the atomic molar ratio of Yb to Er is 1:1; the mass ratio of Yb(NO3)3 and Er(NO3)3 to ethanol is 1:5~10, and the stirring time is 5~10h; the temperature for continued closed heating and stirring until transparent is 80~120℃, the rotation speed is 480~600r / min, and the oil bath time is 4~10h; in the Y2O3-Yb2O3-Er2O3 sol, the atomic molar ratio of Yb+Er∶Y is 3:3~7, and the γ-Y2Si2O7 material does not contain other doping elements.

4. The preparation method according to claim 1, characterized in that, In step (2), the solid content of the SiO2 sol is 15%~40wt%, the particle size is 10~60nm, and the pH value is 7.5~9. During the process of diluting the SiO2 sol with anhydrous ethanol, the mass ratio of SiO2 sol to anhydrous ethanol is 1:1~4.

5. The preparation method according to claim 1, characterized in that, In step (2), the mixing ratio of the diluted SiO2 sol to the Y2O3-Yb2O3-Er2O3 sol satisfies the ratio of Si atoms to Y atoms. 3+ +Yb 3+ +Er 3+ The molar ratio between them is 1:1; the relative molecular mass of the polyethylene glycol is 200~600, and the mass ratio of the polyethylene glycol to the mixed solution is 2~5:

10.

6. The preparation method according to claim 1, characterized in that, In step (2), the heating and stirring method is to first heat and stir in a closed manner for 2 to 4 hours, and then heat and stir in an open manner for 4 to 8 hours. The heating temperature is 60 to 90°C, and the stirring speed is 450 to 540 r / min.

7. The preparation method according to claim 1, characterized in that, In step (3), the internal solution loading of the sealed pressure vessel is 1 / 2 to 2 / 3 of the total volume, the heating temperature after the sealed pressure vessel is sealed is 140 to 180°C, and the holding time is 2 to 6 hours; the drying temperature regime is as follows: holding at 80°C for 2 hours, 100°C for 2 hours, 120°C for 2 hours, 150°C for 1 hour, and 200°C for 1 hour in sequence.

8. The preparation method according to any one of claims 1 to 7, characterized in that, In step (4), the calcination temperature is 1200~1500℃ and the calcination time is 1~6h.

9. A wide-temperature-range γ-Y₂Si₂O₇ material obtained by the preparation method according to any one of claims 1 to 8, characterized in that, Yb is doped in the γ-Y2Si2O7 3+ and Er 3+ Rare earth ions, the phase transition temperature of the γ-Y2Si2O7 to δ-Y2Si2O7 is above 1700℃.

10. The wide-temperature-range γ-Y₂Si₂O₇ material according to claim 9, characterized in that, Yb in the γ-Y2Si2O7 material 3+ and Er 3+ The molar ratio is 1:1, Yb 3+ and Er 3+ Total ions and Y 3+ The molar ratio of ions is 3:3~7, and the γ-Y2Si2O7 material does not contain other doped ions.

Images