Yttrium oxide powder and preparation method thereof

Abstract

The invention provides yttrium oxide powder and a preparation method thereof, and the preparation method comprises the following steps: uniformly mixing yttrium salt and a solvent to obtain a yttrium salt solution, adding a first dispersing agent, and mixing until the first dispersing agent is dissolved in the yttrium salt solution to obtain a first solution; heating the first solution to a first temperature, dropwise adding a precipitant, continuously stirring, and continuously stirring for a preset time after the precipitant is dropwise added to obtain a second solution; standing and aging the second solution, then adding a second dispersing agent into the second solution, mixing, and continuing standing and aging to obtain a third solution; filtering the third solution to obtain a precursor; and washing and drying the precursor to obtain powder, and calcining the powder to obtain the yttrium oxide powder. According to the yttrium oxide powder and the preparation method thereof, agglomeration of the yttrium oxide powder can be reduced, and the yttrium oxide powder which is loose, high in specific surface area and excellent in sintering performance is obtained.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of inorganic ceramic material preparation, and particularly relates to a yttrium oxide powder and a preparation method thereof. BACKGROUND

[0002] Yttrium oxide (Y2O3) powder occupies a key position in the semiconductor field due to excellent dielectric properties, high band gap and chemical stability, can be used as a high-k gate insulating layer to replace traditional silicon dioxide to reduce device leakage current, and can be used as a thin film precursor for atomic layer deposition and chemical vapor deposition for the preparation of thin films of logic chips, power semiconductors and other devices. However, the quality requirements of such semiconductor applications for yttrium oxide powder are extremely strict, and the yttrium oxide powder needs to have high purity, ultra-fine particle size and low agglomeration.

[0003] The coprecipitation method has become a mainstream method for preparing yttrium oxide powder due to simple process, low cost and easy industrialization. However, in the method, the yttrium-based precipitation particles have high surface energy and are prone to agglomeration due to intermolecular forces, and this phenomenon will be further intensified during the aging, drying and calcination processes, resulting in large particle size and poor dispersibility of the powder.

[0004] The prior art mainly uses a single dispersant to solve the agglomeration problem, but the control effect is limited: the adsorption stability of small molecule electrostatic repulsion type dispersants decreases during the aging stage, and it is difficult to continuously inhibit agglomeration; the addition time of high molecular space steric type dispersants is difficult to control, and early addition is easy to interfere with the precipitation reaction, and late addition cannot repair the formed agglomerates. In addition, the dispersant dosage lacks precise matching basis, and the addition time is described vaguely, resulting in poor process repeatability, large product performance fluctuation, and difficulty in meeting the strict requirements of high-end fields on the high dispersibility of the powder. Therefore, in view of the technical problems of the prior art, it is of important industrial application value to develop a yttrium oxide powder preparation method of "double dispersant cooperation + precise process control". SUMMARY

[0005] The application provides a yttrium oxide powder and a preparation method thereof, which can reduce the agglomeration of the yttrium oxide powder and obtain a loose, high specific surface area and excellent sintering performance yttrium oxide powder.

[0006] To solve the above technical problems, the application provides a preparation method of a yttrium oxide powder, which at least comprises the following steps:

[0007] The yttrium salt is uniformly mixed with the solvent to obtain a yttrium salt solution, then a first dispersant is added and mixed until the first dispersant is dissolved in the yttrium salt solution to obtain a first solution;

[0008] After the first solution is heated to a first temperature, a precipitant is added dropwise and stirring is continued, and after the addition of the precipitant is completed, stirring is continued for a preset time to obtain a second solution;

[0009] The second solution is aged, and then a second dispersant is added to the second solution and mixed, and the aging is continued to obtain a third solution;

[0010] The third solution is filtered to obtain a precursor; and

[0011] The precursor is washed and dried to obtain a powder, and then calcination is performed to obtain a yttrium oxide powder.

[0012] In an embodiment of the present application, one or more of the following features is included:

[0013] The concentration of the yttrium salt solution is 0.05 mol / L-1 mol / L;

[0014] The first dispersant is a small molecule electrostatic repulsion type dispersant;

[0015] The small molecule electrostatic repulsion type dispersant includes one or a combination of citric acid, malic acid, tartaric acid or a salt thereof;

[0016] The addition amount of the small molecule electrostatic repulsion type dispersant is 0.3 mol%-2 mol% of yttrium ions;

[0017] In an embodiment of the present application, one or more of the following features is included:

[0018] The first temperature is 30°C-85°C;

[0019] The precipitant includes at least one of oxalic acid, hydroxide, carbonate and ammonia;

[0020] The molar ratio of the precipitant to yttrium ions is (3-10):1;

[0021] The concentration of the precipitant is 0.3 mol / L-5 mol / L;

[0022] The rate of adding the precipitant dropwise to the first solution is 0.5 mL / min-5 mL / min;

[0023] The rate of continuously stirring the precipitant and the first solution is 100 rpm-800 rpm;

[0024] The preset time is 30 min-300 min.

[0025] In an embodiment of the present application, the addition time of the second dispersant is within 0-30 min of the aging stage.

[0026] In an embodiment of the present application, one or more of the following features is included:

[0027] The second dispersant is a high-molecular steric-hindrance dispersant.

[0028] The high-molecular steric-hindrance dispersant includes one of polyvinylpyrrolidone, polyethylene glycol or sodium carboxymethyl cellulose, or a combination thereof.

[0029] The high-molecular steric-hindrance dispersant is added in an amount of 0.05-1 mol% of yttrium ions.

[0030] In an embodiment of the present application, one or more of the following features is included:

[0031] The time for the continued aging is 5-48 hours.

[0032] The solvent for washing the precursor includes one of deionized water, ethanol, isopropanol, acetone and n-propanol, or a combination thereof.

[0033] In an embodiment of the present application, the temperature for drying the precursor is 70-120℃, and the time for drying the precursor is 8-48 hours.

[0034] In an embodiment of the present application, when calcining the powder, the powder is first heated to a calcination temperature at a preset heating rate, and then held for a first time, and then cooled to room temperature at a preset cooling rate to obtain the yttrium oxide powder.

[0035] In an embodiment of the present application, one or more of the following features is included:

[0036] The preset heating rate is 0.5-8℃ / min.

[0037] The calcination temperature is 550-950℃.

[0038] The first time is 2-12 hours.

[0039] The preset cooling rate is 1-10℃ / min.

[0040] The present application also provides a yttrium oxide powder obtained by the above preparation method.

[0041] In summary, the present application provides a kind of yttria powder and preparation method thereof, by adding two kinds of dispersants with different action mechanisms in time period in the process of precipitation reaction, introducing small molecule electrostatic repulsion type dispersant in nucleation stage to quickly adsorb particle surface, increase particle spacing and reduce surface hydroxyl exposure, introducing high molecular space steric type dispersant in particle growth and aging stage to occupy active adsorption site, form permeable isolation layer and continuously shield surface hydroxyl, so as to inhibit primary agglomeration and secondary aggregation respectively, and then finally obtain loose, high specific surface area and excellent sintering performance yttria powder, effectively overcome the defects of uneven particle size, hard agglomeration and sintering performance decline in prior art. BRIEF DESCRIPTION OF DRAWINGS

[0042] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0043] Figure 1 The flow chart of the preparation method of the yttria powder of the present application.

[0044] Figure 2 The scanning electron microscope characterization graph of the yttria powder in Example 1 of the present application.

[0045] Figure 3 The scanning electron microscope characterization graph of the yttria powder in Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0046] The embodiments of the present application will be described in detail below through specific, concrete examples, and those skilled in the art can easily understand other advantages and effects of the present application from the content disclosed in the present specification. The present application can also be implemented or applied in other different specific embodiments, and various modifications or changes can be made to the details in the present specification based on different views and applications without departing from the spirit of the present application.

[0047] It should be understood that the present application can be implemented in different forms, and should not be interpreted as being limited to the embodiments presented herein. On the contrary, these embodiments are provided to make the disclosure complete and complete, and to fully convey the scope of the present application to those skilled in the art.

[0048] The technical solutions of the present application will be further described in detail below in combination with the embodiments, and obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0049] Referring to Figure 1 As shown in the figure, the application provides a preparation method of yttrium oxide powder, at least comprising steps S11-S15.

[0050] Step S11, the yttrium salt is mixed with the solvent to obtain a yttrium salt solution, then the first dispersant is added and mixed until the first dispersant is dissolved in the yttrium salt solution to obtain a first solution.

[0051] Step S12, after the first solution is heated to a first temperature, the precipitant is added dropwise and the stirring is continued, after the addition of the precipitant is completed, the stirring is continued for a preset time to obtain a second solution.

[0052] Step S13, the second dispersant is added to the second solution and mixed, and then the solution is aged for a preset time to obtain a third solution.

[0053] Step S14, the third solution is filtered to obtain a precursor.

[0054] Step S15, the precursor is washed and dried to obtain a powder, and then the powder is calcined to obtain the yttrium oxide powder.

[0055] Referring to Figure 1 As shown in the figure, in an embodiment of the application, in step S11, the yttrium salt and the solvent are mixed to obtain a yttrium salt solution. The yttrium salt includes at least one of soluble yttrium salts such as yttrium nitrate hexahydrate, yttrium chloride and yttrium sulfate, the solvent is deionized water or the like, and the concentration of the yttrium salt solution is 0.05 mol / L-1 mol / L.

[0056] Referring to Figure 1As shown in the embodiment of the present application, after obtaining the yttrium salt solution, in step S11, the first dispersing agent is added to the yttrium salt solution and mixed until the first dispersing agent is completely dissolved in the yttrium salt solution, obtaining a transparent and uniform first solution. The first dispersing agent is a small molecule electrostatic repulsion type dispersing agent, for example, including one or a combination of citric acid, malic acid, tartaric acid or its salt. Because the first dispersing agent has a small molecular weight and a fast diffusion speed, it can quickly enter the gap between particles and uniformly adsorb on the particle surface in the early nucleation stage of the precipitation reaction, immediately establishing a surface charge layer and generating an electrostatic repulsive force. The adsorption layer of the first dispersing agent not only increases the physical distance between particles, reducing collision and agglomeration, but also shields part of the surface hydroxyl groups, reducing the probability of hydroxyl adsorption on the particle surface, and preliminarily forming a surface protection layer. For example, the addition amount of the small molecule electrostatic repulsion type dispersing agent is 0.3mol% to 2mol% of yttrium ions. When the addition amount of the small molecule electrostatic repulsion type dispersing agent is less than 0.3mol% of yttrium ions, it is difficult to form a continuous coating layer, and the dispersion stability decreases significantly, and the particles are easily aggregated in the early stage of the reaction. When the addition amount of the small molecule electrostatic repulsion type dispersing agent is higher than 2mol / L of yttrium ions, the excess dispersing agent will strongly complex with Y 3+ , delaying the precipitation reaction or changing the nucleation kinetics, resulting in uneven particle size and byproduct generation.

[0057] For reference Figure 1 As shown in the embodiment of the present application, after obtaining the first solution, in step S12, the first solution is heated to a first temperature and kept for a period of time, for example, the precipitant is added dropwise to the first solution by peristaltic pump and continuously stirred, and after the dropwise addition is completed, the stirring is continued for a preset time. In the stirring process, the precipitant and the yttrium salt react to generate a precipitate, obtaining a second solution. For example, the first temperature is 30°C to 85°C, the molar ratio of the precipitant to yttrium ions is (3-10):1, the precipitant includes at least one of oxalic acid solution, hydroxide solution, carbonate solution, and ammonia water, the hydroxide includes at least one of sodium hydroxide and potassium hydroxide, the carbonate includes at least one of sodium carbonate and ammonium carbonate, the concentration of the precipitant is 0.3mol / L to 5mol / L, the rate of adding the precipitant dropwise to the first solution is 0.5mL / min to 5mL / min, the rate of continuously stirring the precipitant and the first solution is 100rpm to 800rpm, and the preset time is 30min to 300min. In this embodiment, the reaction process of the precipitant and the yttrium salt is described by taking the precipitant as oxalic acid solution. The oxalic acid solution and the yttrium salt react to generate white and loose yttrium oxalate precipitate.

[0058] For reference Figure 1As shown, in an embodiment of the present application, after obtaining the second solution, the second solution is aged in step S13, then a second dispersant is added to the second solution and mixed, and the aging continues, to obtain a third solution. The second dispersant is a high-molecular steric-hindrance dispersant, such as one or a combination of polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), and sodium carboxymethyl cellulose (CMC-Na). The second dispersant is adsorbed on the particle surface when the precipitation reaction ends and enters the aging stage, and the functional groups on the molecular chain thereof can react with the hydroxyl groups or metal ion centers on the particle surface, to occupy the surface adsorption sites and reduce the adsorption of the surface hydroxyl groups, thereby significantly reducing the possibility of hard agglomeration between the particles, greatly improving the sintering activity of the powder, reducing the sintering temperature, and improving the densification degree of the yttrium oxide sintered body. At the same time, the extended structure of the high-molecular chain provides significant steric hindrance to prevent the powder from agglomerating. The addition amount of the high-molecular steric-hindrance dispersant is 0.05 mol% to 1 mol% of the yttrium ions. When the addition amount of the high-molecular steric-hindrance dispersant is less than 0.05 mol% of the yttrium ions, it is difficult to form a continuous coating layer, and the steric hindrance and hydroxyl shielding effect are insufficient. When the addition amount of the high-molecular steric-hindrance dispersant is more than 1 mol% of the yttrium ions, the viscosity of the system is significantly increased, affecting the solid-liquid separation and washing efficiency, and possibly causing carbon residue pollution after calcination, thereby being not conducive to obtaining high-purity loose yttrium oxide powder.

[0059] Please refer to Figure 1 As shown, in an embodiment of the present application, in step S13, the second dispersant is added within 0-30 min of the aging stage, which is a time window when the particle surface is still active and has not yet significantly agglomerated. If the second dispersant is added too late, the particle agglomeration has become partially irreversible, and the coating effect is reduced. Therefore, adding the second dispersant within this window can obtain the powder with the most uniform particle size distribution and the best dispersibility.

[0060] Please refer to Figure 1 As shown, in an embodiment of the present application, in step S13, the aging continues for 5 h to 48 h. According to the Ostwald ripening principle, during the aging process, unstable small particles are dissolved and redeposited onto more stable particles, thereby spontaneously optimizing the size uniformity and crystalline integrity of the precursor particles, ensuring that the precursor is fully crystallized and the uniformity of the particles is optimized, and the aging time of 5 h to 48 h is the best time window that balances the optimization effect and process efficiency.

[0061] Please refer to Figure 1As shown, in one embodiment of the present invention, after obtaining the precursor, in steps S14 and S15, the third solution is filtered to obtain the precursor. Then, the precursor is washed alternately with, for example, deionized water and organic solvent until the anions in the residual yttrium salt in the precursor are removed. The deionized water has high purity and can efficiently remove most inorganic salt impurities. The organic solvent includes, for example, one or a combination of ethanol, isopropanol, acetone and n-propanol. Since the surface tension of the organic solvent is much lower than that of deionized water, the organic solvent can replace the water on the surface and in the pores of the precursor particles. This can fundamentally avoid the hard agglomeration of particles caused by the huge capillary force generated by water evaporation during the drying process, thereby obtaining a loose and easily dispersed precursor powder. Specifically, in this embodiment, for example, the precursor is first washed with deionized water and then filtered to obtain a first filter cake. Then, the first filter cake is washed a second time with ethanol and filtered again to obtain a second filter cake and filtrate. Next, the filtrate is tested to see if it contains anions from the yttrium salt. If the filtrate still contains anions from the yttrium salt, the filter cake is washed repeatedly with alternating amounts of deionized water and ethanol to remove all anions, such as NO3. - SO4 2- and Cl - At least one of the following. Among them, NO3... - SO4 can be qualitatively detected using the brown ring method. 2- Qualitative detection can be performed using barium chloride solution; Cl - Qualitative detection can be performed using AgNO3 solution.

[0062] Please see Figure 1 As shown, in one embodiment of the present invention, after washing the precursor, in step S15, the precursor is placed in an oven for atmospheric pressure drying to obtain a white powder. The drying temperature of the precursor is, for example, 70℃-120℃, and the drying time is, for example, 8h-48h. In other embodiments of the present invention, spray drying or freeze drying may be used instead of atmospheric pressure drying.

[0063] Please see Figure 1As shown, in an embodiment of the present application, after obtaining the powder, the powder is placed in an alumina crucible, and the crucible is placed in a muffle furnace to calcine the powder and obtain yttrium oxide powder. Specifically, during calcination, the powder is first heated to a calcination temperature at a preset heating rate, and then held for a first time, and then cooled to room temperature at a preset cooling rate, and the crucible is taken out to obtain white yttrium oxide powder from the crucible. The preset heating rate is, for example, 0.5-8 ℃ / min, the calcination temperature is, for example, 550-950 ℃, the first time is, for example, 2-12 h, and the preset cooling rate is, for example, 1-10 ℃ / min. By controlling the calcination temperature and the first time, yttrium oxide grain coarsening caused by high temperature can be avoided, and the stable microstructure formed by the pretreatment can further inhibit hard agglomeration during drying / calcination, so that the step of additional high-energy ball milling is not needed, and impurities brought by the ball milling medium to the yttrium oxide powder are avoided. Specifically, the calcination step can achieve a precise balance between the complete phase transition of the precursor and the maintenance of its nanoscale microstructure. Regarding the calcination temperature, from the thermodynamic point of view, the lower limit value 550 ℃ of the calcination temperature ensures sufficient driving force for the complete decomposition of the precursor, so that it can be completely converted into the target crystal phase, thereby obtaining chemical and phase purity. From the kinetic point of view, the upper limit value 950 ℃ of the calcination temperature is a strict control of the yttrium oxide grain growth behavior. In the solid phase reaction, the grain growth rate is exponentially related to the temperature. A too high calcination temperature (>1000 ℃) will activate significant atomic diffusion, especially surface diffusion and grain boundary migration, leading to rapid coarsening of yttrium oxide grains, and a sharp decrease in the specific surface area and sintering activity of yttrium oxide powder. Therefore, limiting the calcination temperature to below 950 ℃ can maintain the system in a relatively slow grain growth kinetics interval, thereby completing the phase transition while maximizing the high specific surface area and high sintering activity of the yttrium oxide powder. Regarding the first time, limiting the first time to be greater than or equal to 2 h can ensure the complete phase transition, i.e., the completion of the reaction kinetics process. However, a too long first time (>12 h) will also accumulate thermal effects and promote yttrium oxide grain growth. Therefore, limiting the first time to 2-12 h is the optimal process window found between ensuring the completeness of the phase transition and inhibiting grain growth, which are two mutually contradictory factors.

[0064] Please refer to Figure 1 As shown, the present application provides a method for preparing yttrium oxide powder, which adds two kinds of dispersants with different action mechanisms at different time periods during the precipitation reaction. A small-molecule electrostatic repulsion type dispersant is introduced at the nucleation stage to quickly adsorb the particle surface, increase the particle spacing, and reduce the exposure of surface hydroxyl groups. A high-molecular space steric type dispersant is introduced at the particle growth and aging stage to occupy active adsorption sites, form a permeable isolation layer, and continuously shield the surface hydroxyl groups, thereby inhibiting primary agglomeration and secondary aggregation, respectively.

[0065] The combination of the first dispersant and the second dispersant enables the two mechanisms of electrostatic repulsion and steric hindrance to continuously play a role in the whole precipitation process, avoids the problem of weakening effect of a single dispersant at a certain stage, and prevents the interference of the effect caused by the competition for adsorption sites when adding simultaneously. The optimized adding time and proportion control of the combination strategy not only realizes the significant narrowing of the particle size distribution and the long-time maintenance of the dispersibility, but also ensures the normal ripening and crystallization of the particles in the aging process, so that loose, high specific surface area and excellent sintering performance yttrium oxide powder is finally obtained, effectively overcoming the defects of uneven particle size, hard agglomeration and decreased sintering performance in the prior art.

[0066] Referring to Figure 1 The present application also provides a yttrium oxide powder obtained by the above preparation method, which will not be described in detail herein. The specific surface area of the yttrium oxide powder is large, for example, greater than 19 m 2 / g. Moreover, the yttrium oxide powder has high sintering performance, specifically, the relative density of the sintered body obtained by sintering the yttrium oxide powder at 1350°C is, for example, 99.2%-99.8%. In the preparation of the sintered body, the yttrium oxide powder prepared by the present application is first sieved to obtain 200-mesh yttrium oxide powder, then the yttrium oxide powder is dry-pressed into a green body at 5-20 MPa, then the green body is debinded at 600°C for 1 h, then the temperature is increased to 1350°C at a rate of 1-8°C / min, and then the temperature is maintained for 2-10 h, then the temperature is decreased to room temperature at a rate of 0.5-6°C / min, to obtain the sintered body, then the actual density of the sintered body is measured according to the Archimedes drainage method, and the relative density is obtained by comparison with the theoretical density (5.01 g / cm 3 ).

[0067] The present application will be explained in more detail below by reference to examples, which should not be understood as limiting. Suitable modifications can be made within the scope consistent with the gist of the present application, which all fall within the technical scope of the present application.

[0068] Example 1

[0069] Yttrium chloride and deionized water were mixed uniformly to obtain a yttrium salt solution of 0.1 mol / L. Citric acid was weighed as the first dispersant at 0.3 mol% of yttrium ions, and dissolved in the yttrium salt solution to obtain a first solution.

[0070] After heating the first solution to 30°C, 0.3 mol / L oxalic acid solution was added to the first solution at a rate of 2 mL / min, and stirring was continued at a rate of 200 rpm. After the addition was completed, stirring was continued for 30 min to obtain a second solution. The molar ratio of oxalate to yttrium ions was 3:1.

[0071] After obtaining the second solution, the second solution was aged, at the 10th minute of the aging time, 0.05 mol% of yttrium ions, polyvinylpyrrolidone was weighed as a second dispersant, dissolved in the second solution, and continued to be aged for 8 h to obtain a third solution; the third solution was filtered to obtain a precursor. Then deionized water was used to first wash the precursor for the first time and then filter to obtain a first filter cake. Then ethanol was used to continue to wash the first filter cake for the second time and then filter to obtain a second filter cake and a filtrate. Then silver nitrate solution was used to detect whether the filtrate contained Cl - If the filtrate still contained Cl - , the filter cake was continuously washed with deionized water and ethanol alternately until the filtrate did not contain Cl - .

[0072] After washing the precursor, the precursor was placed in an oven at 105°C for normal pressure drying for 9 h to obtain a white powder. The powder was placed in an alumina crucible, and the crucible was placed in a muffle furnace. The powder was heated to 850°C at a rate of 6°C / min, and then held for 2.5 h. Then the powder was cooled to room temperature at a rate of 4°C / min. The crucible was removed, and a white yttrium oxide powder was obtained from the crucible.

[0073] Example 2

[0074] Yttrium nitrate hexahydrate and deionized water were mixed uniformly to obtain a yttrium salt solution of 0.5 mol / L. 1 mol% of yttrium ions, malic acid was weighed as a first dispersant, dissolved in the yttrium salt solution to obtain a first solution.

[0075] After heating the first solution to 45°C, 0.5 mol / L oxalic acid solution was added to the first solution at a rate of 3 mL / min, and stirring was continued at a rate of 300 rpm. After the addition was completed, stirring was continued for 120 min to obtain a second solution. The molar ratio of oxalate to yttrium ions was 7:1.

[0076] After obtaining the second solution, the second solution was aged, at the 3rd minute of the aging time, 1 mol% of yttrium ions, polyvinylpyrrolidone was weighed as a second dispersant, dissolved in the second solution, and continued to be aged for 12 h to obtain a third solution; the third solution was filtered to obtain a precursor. Then deionized water was used to first wash the precursor for the first time and then filter to obtain a first filter cake. Then ethanol was used to continue to wash the first filter cake for the second time and then filter to obtain a second filter cake and a filtrate. Then brown ring method was used to detect whether the filtrate contained NO3 - If the filtrate still contained NO3 - , the filter cake was continuously washed with deionized water and ethanol alternately until the filtrate did not contain NO3 - .

[0077] After washing the precursor, the precursor was placed in an oven at 70°C for normal pressure drying for 48h to obtain white powder. After placing the powder in an alumina crucible, the crucible was placed in a muffle furnace, the powder was heated to 580°C at a rate of 2°C / min, and then held for 12h. Then the powder was cooled to room temperature at a rate of 4°C / min. The crucible was removed, and the white yttrium oxide powder was obtained from the crucible.

[0078] Example 3

[0079] Yttrium sulfate and deionized water were mixed uniformly to obtain a yttrium salt solution of 1 mol / L. Tartaric acid was weighed as a first dispersant at 0.5 mol% of yttrium ions, and dissolved in the yttrium salt solution to obtain a first solution.

[0080] The first solution was heated to 35°C and held, and then 1 mol / L oxalic acid solution was added dropwise to the first solution at a rate of 1 mL / min and stirred at a rate of 500 rpm. After the dropwise addition was completed, the stirring was continued for 300 min to obtain a second solution. The molar ratio of oxalate to yttrium ions was 5:1.

[0081] After obtaining the second solution, the second solution was allowed to stand and age. At the 8th minute of the aging time, sodium carboxymethyl cellulose was weighed as a second dispersant at 0.8 mol% of yttrium ions, dissolved in the second solution, and the aging was continued for 24h to obtain a third solution. The third solution was filtered to obtain a precursor. Then deionized water was used to first wash the precursor for the first time and then filter to obtain a first filter cake. Then ethanol was used to second wash the first filter cake and filter again to obtain a second filter cake and a filtrate. Then barium chloride solution was used to detect whether the filtrate contained SO4 2- If the filtrate still contained SO4 2- , the filter cake was continuously washed with deionized water and ethanol alternately until the filtrate did not contain SO4 2- .

[0082] After washing the precursor, the precursor was placed in an oven at 110°C for normal pressure drying for 8h to obtain white powder. After placing the powder in an alumina crucible, the crucible was placed in a muffle furnace, the powder was heated to 900°C at a rate of 7°C / min, and then held for 6h. Then the powder was cooled to room temperature at a rate of 5°C / min. The crucible was removed, and the white yttrium oxide powder was obtained from the crucible.

[0083] Example 4

[0084] Yttrium nitrate hexahydrate and deionized water were mixed uniformly to obtain a yttrium salt solution of 0.4 mol / L. Sodium citrate was weighed as a first dispersant at 1.5 mol% of yttrium ions, and dissolved in the yttrium salt solution to obtain a first solution.

[0085] The first solution was heated to 65°C and, after being kept at this temperature, 1.5 mol / L oxalic acid solution was added dropwise to the first solution at a rate of 5 mL / min and stirring was continued at a rate of 550 rpm, after the dropwise addition was completed, the stirring was continued for 200 min, and a second solution was obtained. In this process, the molar ratio of oxalate to yttrium ions was 4:1.

[0086] After the second solution was obtained, the second solution was allowed to stand and age, at the 15th min of the aging time, 0.3 mol% of yttrium ions of polyethylene glycol was weighed as a second dispersant, dissolved in the second solution, and the standing and aging was continued for 36 h to obtain a third solution.

[0087] The third solution was filtered to obtain a precursor. Then deionized water was used to first clean the precursor for the first time, and then the first filter cake was obtained by filtering. Then ethanol was used to clean the first filter cake for the second time, and then the second filter cake and filtrate were obtained by filtering again. Then the brown ring method was used to detect whether the filtrate contained NO3 - If the filtrate still contained NO3 - , the filter cake was continuously cleaned with deionized water and ethanol alternately until the filtrate did not contain NO3 - .

[0088] After washing the precursor, the precursor was placed in an oven at 120°C for normal pressure drying for 10 h to obtain a white powder. The powder was placed in an alumina crucible, the crucible was placed in a muffle furnace, the powder was heated to 950°C at a rate of 0.5°C / min, and then the powder was kept at this temperature for 3 h. Then the powder was cooled to room temperature at a rate of 2°C / min, the crucible was taken out, and a white yttrium oxide powder was obtained from the crucible.

[0089] Example 5

[0090] Yttrium nitrate hexahydrate and deionized water were mixed uniformly to obtain a 0.05 mol / L yttrium salt solution. Citric acid was weighed as a first dispersant at 2 mol% of yttrium ions, dissolved in the yttrium salt solution to obtain a first solution.

[0091] The first solution was heated to 75°C and, after being kept at this temperature, 2 mol / L oxalic acid solution was added dropwise to the first solution at a rate of 2 mL / min and stirring was continued at a rate of 750 rpm, after the dropwise addition was completed, the stirring was continued for 180 min, and a second solution was obtained. In this process, the molar ratio of oxalate to yttrium ions was 6:1.

[0092] After the second solution was obtained, the second solution was allowed to stand and age, at the 15th min of the aging time, 0.5 mol% of yttrium ions of sodium carboxymethyl cellulose was weighed as a second dispersant, dissolved in the second solution, and the standing and aging was continued for 48 h to obtain a third solution.

[0093] The third solution is filtered to obtain a precursor. The precursor is then first washed with deionized water and filtered to obtain a first filter cake, and then the first filter cake is further washed with ethanol and filtered again to obtain a second filter cake and a filtrate. The filtrate is then detected by brown ring method to determine whether it contains NO3 - If the filtrate still contains NO3 - , the filter cake is continuously washed with deionized water and ethanol alternately until the filtrate does not contain NO3 - .

[0094] After washing the precursor, the precursor is placed in an oven at 100°C for normal pressure drying for 10h to obtain a white powder. The powder is placed in an alumina crucible, and the crucible is placed in a muffle furnace. The powder is heated to 900°C at a rate of 3°C / min and then kept at 900°C for 6h. Then the powder is cooled to room temperature at a rate of 5°C / min. The crucible is taken out, and a white yttria powder is obtained from the crucible.

[0095] Comparative Example 1

[0096] The difference between the present comparative example and Example 1 is that no first dispersant and second dispersant are added.

[0097] As shown in Table 1, in an embodiment of the present application, the relative density of the yttria sintered body in Examples 1-5 and Comparative Example 1 is tested by, for example, the Archimedes drainage method. Specifically, the yttria powder is sieved to obtain a 200-mesh yttria powder, and then the yttria powder is dry-pressed into a green body at 15MPa. The green body is then debound at 600°C for 1h, and then heated to 1350°C at a rate of 5°C / min and kept at 1350°C for 2h. Then the sintered body is obtained by cooling to room temperature at a rate of 4°C / min. The actual density of the sintered body is measured according to the Archimedes drainage method, and then the relative density is calculated according to the ratio of the actual density to the theoretical density of yttria (5.01g / cm 3 ).

[0098] The actual density of the sintered body is calculated according to the following formula:

[0099] As shown in Table 1, in an embodiment of the present application, the microstructure of the yttria powder in Example 1 and Comparative Example 1 is observed by, for example, a scanning electron microscope. Figure 2 Figure 3 As shown in Table 1, in an embodiment of the present application, the microstructure of the yttria powder in Example 1 and Comparative Example 1 is observed by, for example, a scanning electron microscope. Figure 2 Figure 3 ​​It can be seen that compared with the comparative example 1, the dispersibility of the yttrium oxide powder in the example 1 is better, and the particle is small, thereby indicating that the refinement and homogenization of the yttrium oxide powder can be realized by the preparation method provided in the application.

[0100] As shown in Table 1, in an embodiment of the application, when the specific surface area of the powder is measured by using a specific surface area meter, the standard sample and the sample to be measured are dried at 120 DEG C to remove the surface free water, and the sample to be measured and the standard sample are weighed, and the specific surface area of the powder to be measured is automatically converted by the instrument by comparing the adsorption signal response values of the standard sample and the sample to be measured; and the detection data is recorded after the measurement is completed.

[0101] Table 1, characterization results of the yttrium oxide powder in the example 1-5 and the comparative example 1

[0102] Group Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Sintered body relative density (%) 99.5 99.8 99.4 99.3 99.2 70 Specific surface area (m 2 / g)]]> 23.54 23.86 19.67 21.16 22.22 9.96

[0103] As shown in Table 1, it can be seen from the comparative example 1 and the comparative example 1 that by adding two dispersants with different action mechanisms in different time periods, the specific surface area of the yttrium oxide powder prepared is larger, and the relative density of the sintered body is also higher, thereby indicating that the preparation method provided in the application can improve the specific surface area and the sintering performance of the yttrium oxide powder.

[0104] As shown in Table 1, it can be seen from the comparative example 1-5 that by changing the type of yttrium salt, the concentration of the yttrium salt solution, the type of dispersant, the adding time of the dispersant, the adding amount of the dispersant, the pretreatment temperature, the pretreatment time, the dropping speed of the precipitator, the drying temperature, the calcination temperature and the calcination time and other parameters, the relative density and the specific surface area of the yttrium oxide sintered body can be changed, thereby indicating that by changing the parameters in the preparation process, the sintering performance and the specific surface area of the yttrium oxide powder can be optimized.

[0105] In summary, the application provides a yttrium oxide powder and a preparation method thereof, by adding two dispersants with different action mechanisms in different time periods in the precipitation reaction process, a small-molecule electrostatic repulsion type dispersant is introduced in the nucleation stage to quickly adsorb the particle surface, increase the particle spacing and reduce the surface hydroxyl exposure, a high-molecular space steric type dispersant is introduced in the particle growth and aging stage to occupy the active adsorption site, form a permeable isolation layer and continuously shield the surface hydroxyl, thereby respectively inhibiting the primary agglomeration and the secondary aggregation, and finally a loose, high specific surface area and excellent sintering performance yttrium oxide powder can be obtained, and the defects such as uneven particle size, hard agglomeration and sintering performance decline in the prior art are effectively overcome.

[0106] The above description is only the preferred embodiment of the present application and the explanation of the technical principles applied, and those skilled in the art should understand that the inventive scope of the present application is not limited to the technical solutions formed by the specific combinations of the above technical features, and should also cover other technical solutions formed by the combinations of the above technical features or their equivalent features without departing from the inventive concept, such as the technical solutions formed by the mutual replacement of the above features and the technical features disclosed in the present application (but not limited to) having similar functions.

[0107] In addition to the technical features described in the specification, the remaining technical features are known to those skilled in the art, and in order to highlight the innovative features of the present application, the remaining technical features will not be described here.

Claims

1. A method for preparing yttrium oxide powder, characterized in that, At least the following steps are included: Yttrium salt is mixed evenly with solvent to obtain yttrium salt solution. Then, a first dispersant is added and mixed until the first dispersant dissolves in the yttrium salt solution to obtain a first solution. After heating the first solution to a first temperature, a precipitant is added dropwise while stirring continuously. After the precipitant is completely added, stirring is continued for a preset time to obtain a second solution. The second solution is allowed to stand for aging, then the second dispersant is added to the second solution and mixed, and the solution is allowed to stand for aging again to obtain the third solution; The third solution was filtered to obtain the precursor; as well as The precursor is washed and dried to obtain powder, which is then calcined to obtain yttrium oxide powder.

2. The preparation method according to claim 1, characterized in that, Includes one or more of the following characteristics: The concentration of the yttrium salt solution is 0.05 mol / L to 1 mol / L; The first dispersant is a small molecule electrostatic repulsion dispersant; The small molecule electrostatic repulsion dispersant includes citric acid, malic acid, tartaric acid, or one or a combination thereof, or salts thereof. The amount of the small molecule electrostatic repulsion dispersant added is 0.3 mol% to 2 mol% of yttrium ions.

3. The preparation method according to claim 1, characterized in that, Includes one or more of the following characteristics: The first temperature is 30℃-85℃; The precipitant includes at least one of oxalic acid, hydroxide, carbonate, and ammonia water; The molar ratio of the precipitant to yttrium ions is (3-10):1; The concentration of the precipitant is 0.3 mol / L-5 mol / L; The precipitant is added dropwise to the first solution at a rate of 0.5 mL / min to 5 mL / min; The precipitant and the first solution are continuously stirred at a rate of 100 rpm to 800 rpm; The preset stirring time is 30 min to 300 min.

4. The preparation method according to claim 1, characterized in that, The second dispersant is added within 0-30 minutes of the static aging stage.

5. The preparation method according to claim 1, characterized in that, Includes one or more of the following characteristics: The second dispersant is a sterically hindered polymeric dispersant; The sterically hindered polymeric dispersant includes one or a combination of polyvinylpyrrolidone, polyethylene glycol, or sodium carboxymethyl cellulose. The amount of the sterically hindered polymeric dispersant added is 0.05 mol% to 1 mol of yttrium ions.

6. The preparation method according to claim 1, characterized in that, Includes one or more of the following characteristics: The continued static aging time is 5h-48h; The solvent used to wash the precursor includes one or a combination of deionized water, ethanol, isopropanol, acetone, and n-propanol.

7. The preparation method according to claim 1, characterized in that, The temperature for drying the precursor is 70℃-120℃, and the drying time is 8h-48h.

8. The preparation method according to claim 1, characterized in that, When calcining the powder, the powder is first heated to the calcination temperature at a preset heating rate, then held at that temperature for a first time, and then cooled to room temperature at a preset cooling rate to obtain the yttrium oxide powder.

9. The preparation method according to claim 8, characterized in that, Includes one or more of the following characteristics: The preset heating rate is 0.5℃ / min-8℃ / min; The calcination temperature is 550℃-950℃; The first time period is 2h-12h; The preset cooling rate is 1℃ / min-10℃ / min.

10. A yttrium oxide powder, characterized in that, Obtained by the preparation method according to any one of claims 1-9.

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