A spheroid-like doped ceria, its preparation method and application

Abstract

The present application relates to a kind of spheroidal doped ceria and its preparation method and application, the preparation method includes the following steps: after cerium salt, doped metal salt, solvent, acidic reagent and precipitant are mixed, hydrothermal reaction is carried out, and the precipitate is obtained, the precipitate is calcined, and the spheroidal doped ceria of the present application is obtained;The doped metal salt includes praseodymium salt and / or neodymium salt.The present application uses cerium salt and praseodymium salt and / or neodymium salt as doped metal salt as raw material, by the design of mixing process and reaction procedure and the selection of preparation process, the preparation of spheroidal doped ceria is realized, the doped ceria of nanometer level particle is obtained, and its appearance is regular and particle size is uniform, and, the preparation method used in the present application is simple, reaction time is short, and can be used for mass production.

Description

Technical Field

[0001] This invention relates to the field of nano-rare earth material preparation technology, and in particular to a spherical doped cerium dioxide, its preparation method and application. Background Technology

[0002] Cerium dioxide, as a typical rare earth material, possesses advantages such as a unique crystal structure, excellent redox capabilities, high melting point, strong chemical reactivity, safety, environmental friendliness, and semiconductor properties. It can be widely used in polishing processes, cosmetics, and catalysts, especially in polishing, where it plays a crucial role as the main abrasive in chemical mechanical polishing (CMP). Furthermore, due to its moderate hardness and strong chemical reactivity, it is widely used in semiconductor manufacturing and precision optical processing. In particular, cerium dioxide with a near-spherical or spherical structure, due to its smooth surface and micro-abrasive wear mechanism, can produce better polishing results.

[0003] In addition, the morphology and particle size of cerium dioxide will affect its performance, especially its application in chemical mechanical polishing (CMP) process. Irregular morphology and large particle size deviation of cerium dioxide will result in poor surface smoothness of the polishing material after polishing, and may even make it unusable in the polishing process.

[0004] Currently, cerium dioxide is mainly prepared using solid-phase, liquid-phase, or gas-phase methods. Existing technology CN109761261A discloses a method for preparing cerium dioxide, which uses a mixed solvent containing amines and alcohols to absorb carbon dioxide and prepare a precipitant. The precipitate cerium salt is then used to prepare basic cerium carbonate (CeCO3OH), which is subsequently calcined at low temperature to produce nano-cerium dioxide powder. This method is energy-saving, green, and environmentally friendly. However, the cerium dioxide powder obtained by this method has a sheet-like, cluster-like, and rod-like structure, and it is impossible to prepare cerium dioxide with a regularly shaped, near-spherical structure.

[0005] Existing technology CN102765742A discloses a method for preparing cerium dioxide microspheres, which uses polyelectrolytes as morphology control agents and prepares cerium carbonate by gas-phase diffusion, followed by calcination heat treatment to obtain cerium oxide with high specific surface area. This preparation method is complex, and the uniformity of the morphology and particle size of the obtained cerium dioxide needs further improvement.

[0006] Currently, many studies have shown that introducing elemental doping can obtain cerium dioxide with different morphologies. By introducing doping elements into cerium dioxide, the inherently irregular morphology can be transformed into a regular and specific morphology. However, there is very little research in the existing technology on obtaining high-performance spherical cerium dioxide materials through elemental doping combined with preparation methods.

[0007] Therefore, providing a simple preparation method to obtain spherical doped cerium dioxide with regular morphology and good particle size uniformity has become an urgent problem to be solved. Summary of the Invention

[0008] To address the aforementioned technical problems, the present invention aims to provide a near-spherical doped cerium dioxide, its preparation method, and its applications. Using cerium salts and praseodymium and / or neodymium salts as doping metal salts as raw materials, the present invention achieves the preparation of near-spherical doped cerium dioxide through the design of the mixing process with acidic reagents and precipitants, as well as the selection of reaction steps and preparation processes. This yields nanoscale doped cerium dioxide particles with regular morphology and uniform particle size. Furthermore, the preparation method employed in this invention is simple, has a short reaction time, and can be used for mass production.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a method for preparing spherical doped cerium dioxide, the method comprising the following steps:

[0011] Cerium salt, doped metal salt, solvent, acidic reagent and precipitant are mixed and subjected to hydrothermal reaction to obtain precipitate. The precipitate is then calcined to obtain the spherical doped cerium dioxide.

[0012] The doped metal salts include praseodymium salts and / or neodymium salts.

[0013] This invention uses cerium salts and praseodymium and / or neodymium salts as doping metal salts as raw materials. By designing the mixing process with acidic reagents and precipitants, as well as the reaction steps and the selection of preparation processes, it achieves the preparation of spherical doped cerium dioxide. This method has a simple preparation process, short reaction time, and can be used for mass production. The doped cerium dioxide prepared is in the nanoscale, and its morphology is regular and uniform with uniform particle size. It can be widely used in semiconductor CMP polishing, high-end optical polishing, or cosmetics and other fields.

[0014] In the preparation method provided by this invention, praseodymium and / or neodymium salts are directly mixed with cerium salts to introduce dopant elements praseodymium and / or neodymium. This allows the dopant elements praseodymium and / or neodymium to be uniformly dispersed in the cerium dioxide unit cells, thereby producing near-spherical particles. Secondly, this invention adds an acidic reagent to the mixed solution. On the one hand, this fully dissolves the cerium salts and doped metal salts in the solution; on the other hand, the addition of the acidic reagent controls the pH value of the solution and promotes stable crystallization of the mixed solution, forming crystal nuclei, which is beneficial for forming nanoscale particles with regular morphology and uniform particle size. Furthermore, this invention obtains a precipitate by adding a precipitant to the mixed solution and combining it with a hydrothermal reaction. Under calcination conditions, a near-spherical nanostructured doped cerium dioxide with good morphological uniformity is finally prepared.

[0015] Preferably, the mass ratio of the cerium salt to the solvent is 1:(100-200), for example, 1:100, 1:110, 1:120, 1:130, 1:140, 1:150, 1:160, 1:170, 1:180, 1:190 or 1:200, etc.

[0016] Preferably, in the mixed solution, the molar ratio of cerium element in the cerium salt to doped metal element in the doped metal salt is (1000-100000):1; for example, 1000:1, 5000:1, 10000:1, 20000:1, 30000:1, 40000:1, 50000:1, 60000:1, 70000:1, 80000:1, 90000:1, or 100000:1, etc.

[0017] This invention further regulates the molar ratio of cerium element in the cerium salt to the dopant metal element in the dopant metal salt in the mixed solution obtained by mixing, so as to control the relative addition amount of cerium salt and dopant metal salt. If the molar ratio of the two is too small, the addition amount of dopant metal salt will be too large, which will lead to an increase in metal impurities in the final product, a decrease in the uniformity of nanoparticle morphology, and a decrease in performance. If the ratio of the total relative molecular weight of the two is too large, the addition amount of dopant metal salt will be too small, which will lead to particle morphology deformation, which is not conducive to the formation of spherical particles and a decrease in uniformity.

[0018] Preferably, the cerium salt includes any one or a combination of at least two of cerium nitrate, cerium chloride, cerium hydroxide, or cerium sulfate, with cerium nitrate being the most preferred.

[0019] Preferably, the praseodymium salt includes any one or a combination of at least two of praseodymium nitrate, praseodymium chloride, or praseodymium sulfate, with praseodymium nitrate being the most preferred.

[0020] Preferably, the neodymium salt includes any one or a combination of at least two of neodymium nitrate, neodymium chloride, or neodymium sulfate, with neodymium nitrate being the most preferred.

[0021] The present invention introduces doped metal salts into cerium salts, which is beneficial to the uniform doping of praseodymium and / or neodymium elements in cerium dioxide cells. The choice of salt type in the raw materials will also affect the morphology and yield of the resulting doped cerium dioxide.

[0022] Preferably, the doped metal salt includes praseodymium salt and neodymium salt.

[0023] Preferably, when the doped metal salt includes praseodymium salt and neodymium salt, the molar ratio of praseodymium in the praseodymium salt to neodymium in the neodymium salt is (1-100):1, for example, 1:1, 10:1, 20:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1 or 100:1, etc.

[0024] As a preferred embodiment of the present invention, the acidic reagent includes a first acidic reagent and a second acidic reagent.

[0025] In this invention, two different acidic reagents are further used to mix with cerium salt and praseodymium salt. The first acidic reagent promotes the full dissolution of cerium salt and doped metal salts praseodymium and / or neodymium salt in the mixed solution, thereby ensuring the spherical morphology of the obtained doped cerium dioxide and avoiding the presence of undissolved salts that could lead to impurities in subsequent processes and affect the yield of spherical cerium dioxide. The second acidic reagent is introduced to stabilize the acidity in the mixed solution, further preventing the generation of impurities, and to promote crystallization of the mixed solution, forming crystal nuclei, thereby obtaining spherical doped cerium dioxide with a regular and uniform morphology and particle size. Through the synergistic effect of the first and second acidic reagents, this invention not only ensures the successful preparation of spherical doped cerium dioxide but also effectively improves the morphological uniformity and particle size uniformity of the obtained doped cerium dioxide.

[0026] Preferably, the first acidic reagent includes nitric acid.

[0027] Preferably, the second acidic reagent includes any one of acetic anhydride, acetic acid, phosphoric acid, formic acid, or butyric acid.

[0028] Optionally, the acidic reagents used in this invention are all commercially available, wherein the nitric acid is commercially available concentrated nitric acid.

[0029] Preferably, the volume ratio of the first acidic reagent to the second acidic reagent is 1:(0.4-0.8), for example, 1:0.4, 1:0.5, 1:0.6, 1:0.7 or 1:0.8.

[0030] This invention regulates the volume ratio of the first acidic reagent and the second acidic reagent. If the volume ratio is too small, the content of the first acidic reagent will be low, which will lead to insufficient dissolution of cerium salt and doped metal salt, and the reaction will not start normally. If the volume ratio is too large, the content of the second acidic reagent will be low, which will lead to problems such as morphological deformation of cerium dioxide particles, excessive impurities, and reaction errors, thereby affecting the yield of spherical cerium dioxide.

[0031] Preferably, the volume ratio of the first acidic reagent to the solvent is 1:(50-140), for example, 1:50, 1:60, 1:70, 1:80, 1:90, 1:100, 1:110, 1:120, 1:130 or 1:140, etc.

[0032] Preferably, the precipitant includes a first precipitant and / or a second precipitant.

[0033] Preferably, the precipitant includes a first precipitant and a second precipitant.

[0034] Preferably, when the precipitant includes a first precipitant and a second precipitant, the precipitant is added in one step or in stages.

[0035] Preferably, when the precipitant is added in one step, the hydrothermal reaction is a single-stage hydrothermal reaction.

[0036] Preferably, the specific process of the hydrothermal reaction includes: mixing cerium salt, doped metal salt, solvent and acidic reagent to obtain a first mixture; mixing the first mixture with a first precipitant and a second precipitant to obtain a second mixture; and then subjecting the second mixture to a hydrothermal reaction to obtain a precipitate.

[0037] Preferably, the temperature of the first hydrothermal reaction is 100-300℃, such as 100℃, 120℃, 140℃, 160℃, 180℃, 200℃, 220℃, 240℃, 260℃, 280℃ or 300℃.

[0038] Preferably, the duration of the hydrothermal reaction is 1-12 hours, such as 1 hour, 2 hours, 4 hours, 6 hours, 8 hours, 10 hours, or 12 hours.

[0039] As a preferred technical solution of the present invention, when the precipitant is added in steps, the hydrothermal reaction is a segmented hydrothermal reaction.

[0040] Preferably, the segmented hydrothermal reaction includes a first hydrothermal reaction and a second hydrothermal reaction.

[0041] Preferably, the specific process of the first hydrothermal reaction includes: mixing cerium salt, doped metal salt, solvent and acidic reagent to obtain a first mixture, mixing the first mixture and a first precipitant to obtain a third mixture, and performing a first hydrothermal reaction on the third mixture.

[0042] Preferably, the specific process of the second hydrothermal reaction includes: mixing the second precipitant with the product after the first hydrothermal reaction to obtain a fourth mixture, and performing a second hydrothermal reaction on the fourth mixture to obtain the precipitate.

[0043] The present invention further preferably employs a staged hydrothermal reaction, that is, the first precipitant and the second precipitant are added separately to the mixed solution and then subjected to hydrothermal reactions separately. This is because if the first and second precipitants are added simultaneously, the reaction between the substances will be too intense under hydrothermal conditions, affecting the morphology and particle size of the obtained doped cerium dioxide, thereby leading to a decrease in the yield of spherical products and poor particle size uniformity. The present invention, by adding different types of precipitants to the mixture stepwise through a staged hydrothermal reaction, can effectively control the reaction process, control the morphology and size of the particles, and further improve the yield and particle size uniformity of the obtained spherical cerium dioxide.

[0044] Preferably, the temperatures of the first hydrothermal reaction and the second hydrothermal reaction are independently selected from 100-300℃, such as 100℃, 120℃, 140℃, 160℃, 180℃, 200℃, 220℃, 240℃, 260℃, 280℃ or 300℃.

[0045] Preferably, the time for the first hydrothermal reaction and the second hydrothermal reaction is independently selected from 1-12h, such as 1h, 2h, 4h, 6h, 8h, 10h or 12h.

[0046] Preferably, the hydrothermal reaction is followed by a cooling and separation process.

[0047] In this invention, the separation method is not specifically limited, including but not limited to centrifugation, filtration or sedimentation, etc., and those skilled in the art can choose according to their needs.

[0048] The first precipitant and the second precipitant are independently selected from any one of urea, ammonia, ammonium phosphate, ammonium nitrate or ammonium sulfate.

[0049] Preferably, the first precipitant comprises urea.

[0050] Preferably, the second precipitant includes any one of ammonia, ammonium nitrate, ammonium phosphate, or ammonium sulfate.

[0051] Preferably, the mass ratio of the solvent to the precipitant in the first mixture is (50-100):4, for example, 50:4, 60:4, 70:4, 80:4, 90:4 or 100:4.

[0052] In the mixed solution of the present invention, if too little of the first precipitant is added, the reaction will be too slow, affecting the yield of spherical nanoparticles; if too much of the first precipitant is added, it will affect the uniformity of particle morphology and particle size.

[0053] Preferably, the concentration of the second precipitant is 1-50 wt%, such as 1 wt%, 3 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, or 50 wt%.

[0054] Preferably, the pH of the mixture after adding the precipitant is 7.5-11.0, such as 7.5, 8.0, 8.5, 9.0, 9.5, 10.0, 10.5 or 11.0.

[0055] In this invention, the amount of the second precipitant added is such that the pH of the mixture after the addition of the precipitant is within the above-mentioned preferred range, so as to effectively promote the formation of spherical doped cerium dioxide and ensure the uniformity of the morphology and the sameness of the particle size of the obtained product.

[0056] In this invention, if the amount of precipitant added is too small, the pH of the mixture containing the precipitant will be too low, resulting in insufficient reaction and reduced yield of spherical cerium dioxide; if the amount of precipitant added is too large, the pH of the mixed product will be too high, affecting particle morphology and particle size.

[0057] As a preferred technical solution of the present invention, the specific mixing process for preparing the first mixture includes: mixing the cerium salt with a solvent, adding a doped metal salt and continuing to mix, and then sequentially adding a first acidic reagent and a second acidic reagent to mix, thereby obtaining the first mixture.

[0058] In this invention, the mixing method is not specifically limited, including but not limited to stirring, ultrasonication or ball milling, etc., and those skilled in the art can choose as needed.

[0059] The mixed solution of the present invention improves the doping uniformity of dopant elements by designing a specific mixing process, which is beneficial to obtaining spherical materials with good morphology. Furthermore, the distributed mixing can promote the uniformity of particle size of the resulting product, thus obtaining nanoparticles with uniform size.

[0060] Preferably, the calcination temperature is 600-1300℃, such as 600℃, 700℃, 800℃, 900℃, 1000℃, 1100℃, 1200℃ or 1300℃.

[0061] Preferably, the calcination time is 1-24h, such as 1h, 2h, 4h, 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h or 24h.

[0062] As a further preferred embodiment of the present invention, the preparation method includes the following steps:

[0063] (1) Mix cerium salt and solvent at a mass ratio of 1:(100-200), add doped metal salt at a molar ratio of (1000-100000):1 of cerium element in cerium salt to doped metal element in doped metal salt, mix until the solution is clear and transparent, then add first acid reagent and second acid reagent in sequence and continue mixing until the solution is clear and transparent to obtain the first mixture;

[0064] In the first mixture, the doped metal salt includes praseodymium salt and / or neodymium salt, the volume ratio of the first acidic reagent to the second acidic reagent is 1:(0.4-0.8), and the volume ratio of the first acidic reagent to the solvent is 1:(50-140).

[0065] (2) The first mixture and the first precipitant are mixed at a mass ratio of solvent to precipitant of (50-100):4 to obtain a third mixture. The third mixture is subjected to a first hydrothermal reaction at a temperature of 100-300℃ for 1-12 hours. Then, a second precipitant with a concentration of 1-50wt% is added to the product obtained from the first hydrothermal reaction until the pH of the mixture is 7.5-11.0 to obtain a fourth mixture. The fourth mixture is subjected to a second hydrothermal reaction at a temperature of 100-300℃ for 1-12 hours. After cooling, the mixture is separated to obtain a precipitate.

[0066] The first precipitant includes urea, and the second precipitant includes any one of ammonia, ammonium nitrate, ammonium phosphate, or ammonium sulfate.

[0067] (3) The precipitate is calcined at a temperature of 600-1300℃ for 1-24 hours to obtain the spherical doped cerium dioxide.

[0068] In a second aspect, the present invention provides a spherical doped cerium dioxide, which is prepared by the preparation method described in the first aspect, wherein the doping element in the doped cerium dioxide includes praseodymium and / or neodymium.

[0069] The present invention provides a method for uniformly distributing doping elements praseodymium and / or neodymium in the unit cell of cerium dioxide to obtain doped cerium dioxide with a near-spherical shape, the particle size being at the nanometer level, and having the advantages of regular and uniform morphology and size.

[0070] The spherical doped cerium dioxide provided by this invention can achieve a purity of 5N or higher and a crystallinity of 95% or higher.

[0071] Preferably, the molar ratio of cerium to dopant in the doped cerium dioxide is (1000-100000):1.

[0072] Preferably, the average particle size of the doped cerium dioxide is 20-300 nm, such as 20 nm, 40 nm, 60 nm, 80 nm, 100 nm, 120 nm, 140 nm, 160 nm, 180 nm, 200 nm, 220 nm, 240 nm, 260 nm, 280 nm or 300 nm, and more preferably 20-100 nm.

[0073] Preferably, the doping elements of the doped cerium dioxide include praseodymium and neodymium.

[0074] Preferably, the molar ratio of praseodymium to neodymium is (1-100):1, such as 1:1, 10:1, 20:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1 or 100:1, etc.

[0075] Thirdly, the present invention provides an application of spherical doped cerium dioxide as described in the second aspect, wherein the spherical doped cerium dioxide is used in semiconductor polishing, optical polishing or cosmetics.

[0076] The spherical doped cerium dioxide provided by this invention can be applied to any field that can be conceived by those skilled in the art.

[0077] Compared with the prior art, the present invention has at least the following beneficial effects:

[0078] (1) This invention uses cerium salt and praseodymium salt and / or neodymium salt as doping metal salts as raw materials. By designing the mixing process with acidic reagents and precipitants and the reaction process, combined with the selection of preparation process, spherical doped cerium dioxide is prepared. The preparation process is simple, the reaction time is short, and it can be used for mass production. The doped cerium dioxide prepared is nanoscale particles, and its morphology is regular and uniform and the particle size is uniform. It can be widely used in semiconductor CMP polishing, high-end optical polishing or cosmetics and other fields.

[0079] (2) The present invention further preferably employs a segmented hydrothermal reaction, that is, the first precipitant and the second precipitant are added separately to the mixed solution and then subjected to hydrothermal reactions separately. This is because if the first precipitant and the second precipitant are added simultaneously under hydrothermal reaction conditions, the reaction between the substances will be too intense, affecting the morphology and particle size of the obtained doped cerium dioxide, thereby leading to a decrease in the yield of spherical products and a deterioration in particle size uniformity. The present invention, by adding different types of precipitants to the mixture stepwise through a segmented hydrothermal reaction, can effectively control the reaction process, control the morphology and size of the particles, and further improve the yield and particle size uniformity of the obtained spherical cerium dioxide.

[0080] (3) The present invention provides that the doping elements praseodymium and / or neodymium are uniformly distributed in the unit cell of cerium dioxide to obtain spherical doped cerium dioxide with a particle size at the nanometer level, and has the advantages of regular and uniform morphology and size. Attached Figure Description

[0081] Figure 1 This is a scanning electron microscope image of the spherical doped cerium dioxide provided in Example 1. Detailed Implementation

[0082] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0083] The following examples use 65 wt% nitric acid, 36 wt% acetic acid, and 85 wt% phosphoric acid.

[0084] Example 1

[0085] This embodiment provides a method for preparing spherical praseodymium-doped cerium dioxide, the specific steps of which are as follows:

[0086] (1) Cerium nitrate and deionized water are mixed at a mass ratio of 1:150. Then, praseodymium nitrate is added at a molar ratio of cerium in cerium nitrate to praseodymium in praseodymium nitrate of 10000:1. Stirring continues until the solution is clear and transparent. Then, nitric acid and acetic anhydride are added in sequence during stirring. Stirring continues until the solution is clear and transparent again to obtain the first mixture. The volume ratio of nitric acid to acetic anhydride added to the solution is 1:0.5, and the volume ratio of nitric acid to deionized water is 1:120.

[0087] (2) The first mixture and urea are mixed at a mass ratio of 20:1 for deionized water to urea in the first mixture to obtain the second mixture. The second mixture is subjected to a first hydrothermal reaction at 200°C for 6 hours. Then, 25wt% ammonia water is added to the product obtained from the first hydrothermal reaction until the pH of the mixture is 9 to obtain the third mixture. The third mixture is subjected to a second hydrothermal reaction at 200°C for 6 hours. Then, the obtained product is cooled to 30°C and centrifuged at 5000rpm for 2 hours. The solid is taken to obtain the precipitate.

[0088] (3) The precipitate obtained in step (2) is calcined at 1000℃ for 12h to obtain spherical praseodymium-doped cerium dioxide, wherein the molar ratio of cerium to praseodymium in the spherical praseodymium-doped cerium dioxide is 10000:1 and the average particle size of the praseodymium-doped cerium dioxide is 100nm.

[0089] Example 2

[0090] This embodiment provides a method for preparing spherical neodymium-doped cerium dioxide, the specific steps of which are as follows:

[0091] (1) Cerium nitrate and deionized water are mixed at a mass ratio of 1:100. Then, neodymium nitrate is added at a molar ratio of cerium in cerium nitrate to neodymium in neodymium nitrate of 100000:1. Stirring continues until the solution is clear and transparent. Then, nitric acid and acetic acid are added in sequence during the stirring process and stirring continues until the solution is clear and transparent again to obtain the first mixture. The volume ratio of nitric acid to acetic acid added to the solution is 1:0.8, and the volume ratio of nitric acid to deionized water is 1:60.

[0092] (2) The first mixture and urea are mixed at a mass ratio of 15:1 for deionized water to urea in the first mixture to obtain the second mixture. The second mixture is subjected to a first hydrothermal reaction at 300°C for 2 hours. Then, 10wt% ammonia water is added to the product obtained from the first hydrothermal reaction until the pH of the mixture is 8 to obtain the third mixture. The third mixture is subjected to a second hydrothermal reaction at 300°C for 2 hours. Then, the obtained product is cooled to 25°C and centrifuged at 20000rpm for 0.5 hours. The solid is taken to obtain the precipitate.

[0093] (3) The precipitate obtained in step (2) is calcined at 1300℃ for 3 hours to obtain spherical neodymium-doped cerium dioxide, wherein the molar ratio of cerium to neodymium in the spherical neodymium-doped cerium dioxide is 100000:1 and the average particle size of neodymium-doped cerium dioxide is 60nm.

[0094] Example 3

[0095] This embodiment provides a method for preparing spherical cerium dioxide simultaneously doped with praseodymium and neodymium, the specific steps of which are as follows:

[0096] (1) Cerium nitrate and deionized water are mixed at a mass ratio of 1:200. Then, praseodymium nitrate and neodymium nitrate are added at a molar ratio of 1000:1, where the total molar ratio of praseodymium in praseodymium nitrate to neodymium in neodymium nitrate is praseodymium:ne. The molar ratio of praseodymium in praseodymium nitrate to neodymium in neodymium nitrate is 3:1. Stirring continues until the solution is clear and transparent. Then, nitric acid and phosphoric acid are added sequentially during stirring and stirring continues until the solution is clear and transparent again, thus obtaining the first mixture. The volume ratio of nitric acid to phosphoric acid added to the solution is 1:0.4, and the volume ratio of nitric acid to deionized water is 1:140.

[0097] (2) The first mixture and urea are mixed at a solvent-to-urea mass ratio of 25:1 to obtain the second mixture. The second mixture is subjected to a first hydrothermal reaction at 100°C for 10 hours. Then, 30wt% ammonia water is added to the product obtained from the first hydrothermal reaction until the pH of the mixture is 11 to obtain the third mixture. The third mixture is subjected to a second hydrothermal reaction at 100°C for 2 hours. Then, the obtained product is cooled to 25°C and centrifuged at 20000rpm for 0.5 hours. The solid is taken to obtain the precipitate.

[0098] (3) The precipitate obtained in step (2) is calcined at 600℃ for 18h to obtain spherical cerium dioxide simultaneously doped with praseodymium and neodymium. The ratio of the molar amount of cerium to the total molar amount of praseodymium and neodymium in the spherical cerium dioxide simultaneously doped with praseodymium and neodymium is 1000:1, the molar amount of praseodymium to neodymium is 3:1, and the average particle size of the praseodymium-doped and neodymium-doped cerium dioxide is 60nm.

[0099] Example 4

[0100] The only difference between this embodiment and Example 1 is that, in the preparation method provided in this embodiment, cerium nitrate used in step (1) of Example 1 is replaced with cerium chloride, and praseodymium nitrate is replaced with praseodymium chloride. All other process parameters are the same as in Example 1.

[0101] Example 5

[0102] The only difference between this embodiment and Example 1 is that, in the preparation method provided in this embodiment, cerium nitrate used in step (1) of Example 1 is replaced with cerium sulfate, and praseodymium nitrate is replaced with praseodymium sulfate. All other process parameters are the same as in Example 1.

[0103] Example 6

[0104] The only difference between this embodiment and Example 1 is that in the preparation method provided in this embodiment, the molar ratio of cerium in cerium nitrate to praseodymium in praseodymium nitrate in step (1) is 900:1. All other process parameters are the same as in Example 1.

[0105] Example 7

[0106] The only difference between this embodiment and Example 1 is that in the preparation method provided in this embodiment, the molar ratio of cerium in cerium nitrate to praseodymium in praseodymium nitrate in step (1) is 101000:1 when praseodymium nitrate is added. All other process parameters are the same as in Example 1.

[0107] Example 8

[0108] The only difference between this embodiment and Example 1 is that, in the preparation method provided in this embodiment, the volume ratio of nitric acid to acetic anhydride in the mixed solution in step (1) is 1:0.3. All other process parameters are the same as in Example 1.

[0109] Example 9

[0110] The only difference between this embodiment and Example 1 is that, in the preparation method provided in this embodiment, the volume ratio of nitric acid to acetic anhydride in the mixed solution in step (1) is 1:0.9. All other process parameters are the same as in Example 1.

[0111] Example 10

[0112] The difference between this embodiment and Example 1 is that the addition of acetic anhydride to the mixed solution in step (1) is omitted in the preparation method provided in this embodiment. All other process parameters are the same as in Example 1.

[0113] Example 11

[0114] The only difference between this embodiment and Example 1 is that in the preparation method provided in this embodiment, step (2) involves mixing the first mixture and urea at a mass ratio of deionized water to urea of ​​10:1. All other process parameters are the same as in Example 1.

[0115] Example 12

[0116] The only difference between this embodiment and Example 1 is that in the preparation method provided in this embodiment, step (2) involves mixing the first mixture and urea at a mass ratio of 55:2 for deionized water to urea in the first mixture. All other process parameters are the same as in Example 1.

[0117] Example 13

[0118] The only difference between this embodiment and Embodiment 1 is that in the preparation method provided in this embodiment, the addition of urea is omitted in step (2), that is, step (2) adopts the following preparation process:

[0119] Add 25wt% ammonia water to the first mixture obtained in step (1) until the pH of the mixture is 9 to obtain the second mixture. Perform a second hydrothermal reaction on the second mixture at 200°C for 6 hours. Then, cool the obtained product to 30°C and centrifuge at 5000rpm for 2 hours to obtain the solid and precipitate.

[0120] All other process parameters are the same as in Example 1.

[0121] Example 14

[0122] The only difference between this embodiment and Example 1 is that in the preparation method provided in this embodiment, urea and ammonia are added in one step in step (2), and correspondingly, the hydrothermal reaction is carried out in one stage. That is, step (2) adopts the following preparation process:

[0123] Urea and ammonia water with a concentration of 25 wt% were added to the first mixture obtained in step (1) until the pH of the mixture was 9, to obtain a second mixture, wherein the mass ratio of deionized water to urea in the first mixture was 20:1. The second mixture was subjected to a second hydrothermal reaction at a temperature of 200°C for 6 h. Then, the obtained product was cooled to 30°C and centrifuged at a rate of 5000 rpm for 2 h. The solid was taken to obtain the precipitate.

[0124] All other process parameters are the same as in Example 1.

[0125] Example 15

[0126] The only difference between this embodiment and Example 1 is that in the preparation method provided in this embodiment, the preparation method of the first mixture in step (1) is replaced by directly mixing and stirring cerium nitrate, deionized water, praseodymium nitrate, nitric acid, acetic anhydride and urea together to obtain the first mixture. All other process parameters are the same as in Example 1.

[0127] Comparative Example 1

[0128] The only difference between this comparative example and Example 1 is that the preparation method provided in this comparative example omits the addition of praseodymium nitrate to the first mixture in step (1). All other process parameters are the same as in Example 1.

[0129] Comparative Example 2

[0130] The only difference between this comparative example and Example 2 is that the addition of neodymium nitrate to the first mixture in step (1) is omitted in the preparation method provided in this comparative example. All other process parameters are the same as in Example 2.

[0131] Comparative Example 3

[0132] The only difference between this comparative example and Example 1 is that the preparation method provided in this comparative example omits the addition of the acidic reagent composed of nitric acid and acetic anhydride in the first mixture in step (1). All other process parameters are the same as in Example 1.

[0133] Test method:

[0134] (1) Particle size dispersion: The particle size of the doped cerium dioxide or cerium dioxide particles obtained in the above examples and comparative examples was measured by laser diffraction using a laser particle size analyzer, and the D10, D50 and D90 of the particles obtained in the above examples and comparative examples were calculated. The particle size dispersion was calculated using D10, D50 and D90. The calculation formula is: dispersion = (D90-D10) / D50. The results are shown in Table 1.

[0135] (2) Yield of spheroid-shaped doped cerium dioxide: The yield of spheroid-shaped doped cerium dioxide obtained in the above examples and comparative examples was determined. The calculation formula is: Yield of spheroid-shaped doped cerium dioxide = mass of spheroid-shaped doped cerium dioxide in the product / mass of the total product. The results are shown in Table 1.

[0136] Table 1

[0137]

[0138] The test results show that:

[0139] (1) As can be seen from Examples 1 to 3, the present invention uses cerium salt and praseodymium salt and / or neodymium salt as doped metal salt as raw materials. By designing the mixing process with acidic reagent and precipitant and the reaction process, combined with the selection of preparation process, the preparation of spherical doped cerium dioxide is achieved, and nano-sized doped cerium dioxide particles are obtained. Furthermore, the morphology is regular and the particle size is uniform. Moreover, the preparation method adopted by the present invention is simple, has a short reaction time, and can be used for mass production.

[0140] The specific morphology of the doped cerium dioxide obtained in Example 1 is as follows: Figure 1 As shown in the figure, the doped cerium dioxide obtained by the preparation method designed in this invention has the same spherical morphology, uniform particle size, and excellent particle size uniformity.

[0141] (2) As can be seen from Examples 1 and 4-5, if the raw material is a chloride salt, it is difficult to remove the chlorine element, which affects the yield of the material and thus affects the subsequent application of doped cerium dioxide; while if the raw material is a sulfate salt, the reaction process will be prolonged and the operation will be more difficult because the solubility of praseodymium sulfate is not as good as that of praseodymium nitrate.

[0142] (3) As can be seen from Examples 1 and 6-7, the present invention further regulates the molar ratio of cerium element in cerium salt to doped metal element in doped metal salt in the mixed solution obtained by mixing, so as to regulate the relative addition amount of cerium salt and doped metal salt. If the molar ratio of the two is too small, the addition amount of doped metal salt will be too large, which will lead to an increase in metal impurities in the final product, thereby reducing the uniformity of nanoparticle morphology and performance. If the ratio of the total relative molecular weight of the two is too large, the addition amount of doped metal salt will be too small, which will lead to particle morphology deformation, which is not conducive to the formation of spherical particles and reduces the uniformity of particle size.

[0143] (4) As can be seen from Examples 1 and 8-10, the present invention further regulates the volume ratio of the first acidic reagent and the second acidic reagent. If the volume ratio is too small and the content of the first acidic reagent is low, the cerium salt will not dissolve sufficiently and the reaction will not start normally. If the volume ratio is too large and the content of the second acidic reagent is low, the morphology of the cerium dioxide particles will be deformed, there will be too many impurities, and the reaction will fail, thus affecting the yield of spherical cerium dioxide. Even when the addition of the second acidic reagent is omitted in this application, the yield of spherical cerium dioxide will be severely reduced.

[0144] (5) As can be seen from Examples 1 and 11-13, in the mixed solution of the present invention, if too much of the first precipitant is added, it will affect the uniformity of particle morphology and particle size; if too little of the first precipitant is added, the reaction will be too slow and the yield will decrease; if the amount of urea added is directly omitted, it will lead to a decrease in particle uniformity and the yield of spherical cerium dioxide particles, and a decrease in the controllability of particle morphology.

[0145] (6) As can be seen from Examples 1 and 14, compared with adding ammonia and urea to the mixed solution at the same time for a single hydrothermal reaction, the present invention further preferably uses the stepwise addition of urea and ammonia for a segmented hydrothermal reaction. This can avoid the reaction between substances being too intense when the two are added at the same time and under hydrothermal reaction conditions, which would affect the morphology and particle size of the doped cerium dioxide, resulting in a decrease in the yield of spherical products and a decrease in particle size uniformity.

[0146] (7) As can be seen from Examples 1 and 15, compared with the process of mixing the components of the first mixture together, the present invention further sets up a distribution mixing process to obtain the first mixture, which is beneficial to obtain a spherical material with good morphology, improve the doping uniformity of the doping elements, and is beneficial to obtain a spherical material with good morphology. Furthermore, stepwise mixing can promote the uniformity of particle size of the obtained product and obtain nanoparticles with uniform size.

[0147] (8) By comparing Example 1 and Comparative Example 1, Example 2 and Comparative Example 2, it can be seen that if the addition of praseodymium nitrate or neodymium nitrate is omitted in the present invention, the spherical cerium dioxide material cannot be formed, and the morphology of the formed cerium dioxide is irregular rod-shaped or amorphous.

[0148] (9) By comparing Example 1 and Comparative Example 3, it can be seen that if the addition of acidic reagent is omitted in the present invention, the morphological uniformity and particle size uniformity of doped cerium dioxide will be worse, the particle size of its structure will be larger, and nanoscale spherical particles cannot be obtained.

[0149] In summary, this invention uses cerium salts and praseodymium and / or neodymium salts as doping metal salts as raw materials. Through the design of the mixing process with acidic reagents and precipitants, as well as the selection of reaction steps and preparation processes, it achieves the preparation of spherical doped cerium dioxide. This method has a simple preparation process, short reaction time, and can be used for mass production. The doped cerium dioxide obtained is in the nanoscale, and its morphology is regular and uniform with uniform particle size. It can be widely used in semiconductor CMP polishing, high-end optical polishing, or cosmetics and other fields.

[0150] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing spherical doped cerium dioxide for chemical mechanical polishing, characterized in that, The preparation method includes the following steps: Cerium salt, doped metal salt, solvent, acidic reagent and precipitant are mixed and subjected to hydrothermal reaction to obtain precipitate. The precipitate is then calcined to obtain the spherical doped cerium dioxide. The doped metal salts include praseodymium salts and / or neodymium salts; The molar ratio of cerium in the cerium salt to the doped metal in the doped metal salt is (1000-100000):1; The acidic reagent includes a first acidic reagent and a second acidic reagent, and the volume ratio of the first acidic reagent to the second acidic reagent is 1:(0.4-0.8). The first acidic reagent includes nitric acid, and the second acidic reagent includes any one of acetic anhydride, formic acid, phosphoric acid, acetic acid, or butyric acid.

2. The preparation method according to claim 1, characterized in that, The mass ratio of the cerium salt to the solvent is 1:(100-200).

3. The preparation method according to claim 1, characterized in that, The cerium salt includes any one or a combination of at least two of cerium nitrate, cerium chloride, cerium hydroxide, or cerium sulfate.

4. The preparation method according to claim 3, characterized in that, The cerium salt is cerium nitrate.

5. The preparation method according to claim 1, characterized in that, The praseodymium salt includes any one or a combination of at least two of praseodymium nitrate, praseodymium chloride, or praseodymium sulfate.

6. The preparation method according to claim 5, characterized in that, The praseodymium salt is praseodymium nitrate.

7. The preparation method according to claim 1, characterized in that, The neodymium salt includes any one or a combination of at least two of neodymium nitrate, neodymium chloride, or neodymium sulfate.

8. The preparation method according to claim 7, characterized in that, The neodymium salt is neodymium nitrate.

9. The preparation method according to claim 1, characterized in that, The doped metal salts include praseodymium salts and neodymium salts.

10. The preparation method according to claim 9, characterized in that, When the doped metal salt includes praseodymium salt and neodymium salt, the molar ratio of praseodymium in the praseodymium salt to neodymium in the neodymium salt is (1-100):

1.

11. The preparation method according to claim 1, characterized in that, The volume ratio of the first acidic reagent to the solvent is 1:(50-140).

12. The preparation method according to claim 1, characterized in that, The precipitant includes a first precipitant and / or a second precipitant.

13. The preparation method according to claim 12, characterized in that, The precipitant includes a first precipitant and a second precipitant.

14. The preparation method according to claim 13, characterized in that, When the precipitant includes a first precipitant and a second precipitant, the precipitant is added in either a one-step method or a step-by-step method.

15. The preparation method according to claim 14, characterized in that, When the precipitant is added in one step, the hydrothermal reaction is a single-stage hydrothermal reaction.

16. The preparation method according to claim 15, characterized in that, The specific process of the hydrothermal reaction includes: mixing cerium salt, doped metal salt, solvent and acidic reagent to obtain a first mixture; mixing the first mixture with a first precipitant and a second precipitant to obtain a second mixture; and then performing a hydrothermal reaction to obtain a precipitate.

17. The preparation method according to claim 16, characterized in that, The temperature of the first hydrothermal reaction is 100-300℃.

18. The preparation method according to claim 16, characterized in that, The duration of the hydrothermal reaction is 1-12 hours.

19. The preparation method according to claim 14, characterized in that, When the precipitant is added in steps, the hydrothermal reaction is a segmented hydrothermal reaction.

20. The preparation method according to claim 19, characterized in that, The segmented hydrothermal reaction includes a first hydrothermal reaction and a second hydrothermal reaction.

21. The preparation method according to claim 20, characterized in that, The specific process of the first hydrothermal reaction includes: mixing cerium salt, doped metal salt, solvent and acidic reagent to obtain a first mixture; mixing the first mixture and a first precipitant to obtain a third mixture; and performing a first hydrothermal reaction on the third mixture.

22. The preparation method according to claim 20, characterized in that, The specific process of the second hydrothermal reaction includes: mixing the second precipitant with the product of the first hydrothermal reaction to obtain a fourth mixture, and performing a second hydrothermal reaction on the fourth mixture to obtain the precipitate.

23. The preparation method according to claim 20, characterized in that, The temperatures of the first and second hydrothermal reactions are independently selected from 100-300℃.

24. The preparation method according to claim 20, characterized in that, The time for the first hydrothermal reaction and the second hydrothermal reaction is independently selected from 1 to 12 hours.

25. The preparation method according to claim 1, characterized in that, The hydrothermal reaction is followed by a cooling and separation process.

26. The preparation method according to claim 12, characterized in that, The first precipitant and the second precipitant are independently selected from any one of urea, ammonia, ammonium nitrate, ammonium phosphate or ammonium sulfate.

27. The preparation method according to claim 26, characterized in that, The first precipitant includes urea.

28. The preparation method according to claim 26, characterized in that, The second precipitant includes any one of ammonia, ammonium nitrate, ammonium phosphate, or ammonium sulfate.

29. The preparation method according to claim 16 or 21, characterized in that, The mass ratio of the solvent to the precipitant in the first mixture is (50-100):

4.

30. The preparation method according to claim 12, characterized in that, The concentration of the second precipitant is 1-50 wt%.

31. The preparation method according to claim 16 or 22, characterized in that, The pH of the mixture after adding the precipitant is 7.5-11.

0.

32. The preparation method according to claim 16 or 21, characterized in that, The specific mixing process for preparing the first mixture includes: mixing the cerium salt with a solvent, adding a doped metal salt and continuing to mix, and then sequentially adding a first acidic reagent and a second acidic reagent to mix, thereby obtaining the first mixture.

33. The preparation method according to claim 1, characterized in that, The calcination temperature is 600-1300℃.

34. The preparation method according to claim 1, characterized in that, The calcination time is 1-24 hours.

Images