Zirconia sol and method for producing zirconia sol

Abstract

A zirconia sol in which the crystallite diameter A on the monoclinic (-111) plane is 5.0 nm or more and 50.0 nm or less, the crystallite diameter B on the monoclinic (111) plane is 5.0 nm or more and 50.0 nm or less, and the crystallite diameter ratio X represented by the following formula 1 is 0.5 or more and 0.95 or less. <Formula 1> [Crystallite diameter ratio X] = [Crystallite diameter A on the monoclinic (-111) plane] / [Crystallite diameter B on the monoclinic (111) plane] However, the crystallite diameter A and the crystallite diameter B are values calculated from powder X-ray diffraction measurement and analysis of the measurement.

Description

Technical Field

[0001] The present invention relates to a zirconia sol and a method for producing the zirconia sol.

Background Art

[0002] Zirconia sols are used in raw material powders for fine ceramics, precision abrasives, cosmetics, fillers for paints, zirconia thin films, etc. (see, for example, Patent Documents 1 to 5).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to provide a zirconia sol more suitable as abrasive grains, and also to provide a method for producing the zirconia sol.

Means for Solving the Problems

[0005] The present invention provides the following. [1] The crystallite diameter A on the monoclinic (-111) plane is 5.0 nm or more and 50.0 nm or less, The crystallite diameter B on the monoclinic (111) plane is 5.0 nm or more and 50.0 nm or less, A zirconia sol characterized in that the crystallite size ratio X represented by the following formula 1 is 0.5 or more and 0.95 or less. <Formula 1> [Crystallite size ratio X]=[Crystallite size A on the monoclinic (-111) plane] / [Crystallite size B on the monoclinic (111) plane] However, the crystallite size A and the crystallite size B are values calculated from powder X-ray diffraction measurement and analysis of the measurement.

[0006] Since the crystallite size A is 5.0 nm or more and the crystallite size B is 5.0 nm or more, it is possible to suppress burial in the polishing pad and maintain a high polishing rate. In addition, since the crystallite size A is 50.0 nm or less and the crystallite size B is 50.0 nm or less, the intrusion resistance into the polished surface and the pad interface can be reduced. Since the intrusion resistance can be reduced, the instantaneous pressure applied to the contact point can be reduced. As a result, the polishing rate can be maintained high and the surface roughness of the surface to be polished can be reduced.

[0007] In addition, since the crystallite size ratio X is 0.95 or less, the polishing rate can be maintained high. The reason for this is speculated by the present inventors as follows. When the crystallite size ratio X is 0.95 or less, the monoclinic crystal becomes a rectangular parallelepiped or rod shape with a larger aspect ratio. The rectangular parallelepiped and rod-shaped crystals are more difficult to rotate compared to spherical crystals (crystals with a crystallite size ratio X of 1). As a result, the frictional resistance with the surface to be polished increases, and the effect of improving the polishing rate is exhibited.

[0008] The zirconia sol in which the crystallite size A is 5.0 nm or more and 50.0 nm or less, the crystallite size B is 5.0 nm or more and 50.0 nm or less, and the crystallite size ratio X is 0.5 or more and 0.95 or less can be expected to have a higher rate and higher smoothness (low surface roughness) than existing products in precision polishing of semiconductors and the like. In particular, in polishing of SiC or the like with high hardness, a higher rate and higher smoothness (low surface roughness) can be expected than existing products.

[0009] Furthermore, the present invention provides the following. [2] The zirconia sol according to [1] above, containing a tetragonal phase with a volume fraction of 2.0% or more and 90.0% or less.

[0010] When the volume fraction of the tetragonal phase is 2.0% or more and 90.0% or less, the surface roughness of the surface to be polished can be made smaller while maintaining a high polishing rate. Regarding the reason, the present inventors presume as follows. The tetragonal phase has the property of undergoing a phase transition to the monoclinic phase under pressure, and is accompanied by a volume expansion of several percent when undergoing the phase transition to the monoclinic phase. Therefore, when the zirconia sol is exposed to pressure at the interface between the pad and the surface to be polished, a part of the tetragonal phase undergoes a phase transition to the monoclinic phase, and the volume expansion at that time cleaves the aggregation of crystallites and loosens the aggregation. As a result, the exposure pressure is relaxed. As a result, since it occurs intermittently during polishing, the instantaneous overpressure on the surface to be polished by the abrasive grains is suppressed, and the surface roughness can be made smaller.

[0011] Furthermore, the present invention provides the following. [3] The zirconia sol according to [1] or [2] above, wherein the crystallite size ratio Y represented by the following formula 2 is 0.3 or more and 1.2 or less. <Formula 2> [Crystallite size ratio Y] = [Crystallite size A on the monoclinic (-111) plane] / [Crystallite size C on the tetragonal (101) plane] However, the crystallite size C is a value calculated from powder X-ray diffraction measurement and analysis of the measurement.

[0012] When the crystallite size ratio Y is 0.3 or more and 1.2 or less, the surface roughness of the surface to be polished can be made smaller. Regarding the reason, the present inventors presume as follows. When the crystallite size ratio Y is 0.3 or more and 1.2 or less, the phase transition is likely to be induced. That is, the instantaneous overpressure is more suppressed. As a result, the surface roughness becomes smaller.

[0013] Furthermore, the present invention provides the following. [4] Particle size D 50is in the range of 5 nm or more and less than 50 nm, the zirconia sol according to any one of the above [1] to [3], wherein the ratio X obtained by the following procedure is 40% or more. <Procedure> Obtain a transmission electron microscope image containing 20 or more isolated particles. For each isolated particle in the transmission electron microscope image, perform the following operations 1) to 5). 1) Determine the circumscribed circle and the inscribed circle having the same center as the circumscribed circle. 2) Determine the ratio [(diameter of the circumscribed circle) / (diameter of the inscribed circle)] of the obtained diameter of the circumscribed circle to the diameter of the inscribed circle. 3) For all isolated particles in the transmission electron microscope image, determine the ratio [(diameter of the circumscribed circle) / (diameter of the inscribed circle)]. 4) Count the number of isolated particles A whose ratio [(diameter of the circumscribed circle) / (diameter of the inscribed circle)] is 2.0 or more. 5) Determine the ratio X of the isolated particles A to all isolated particles. (Ratio X (%)) = [(number of isolated particles A) / (total number of isolated particles)] × 100

[0014] Particles with a ratio [(diameter of the circumscribed circle) / (diameter of the inscribed circle)] of 2.0 or more can be said to be more angular and distorted-shaped particles. According to the configuration of the above [4], the ratio X is 40% or more, and a certain number or more of angular and distorted-shaped particles are included. A zirconia sol having such particles is more useful as an abrasive grain.

[0015] Furthermore, the present invention provides the following. [5] Step A of dropwise adding aqueous ammonia to an aqueous zirconium oxychloride solution for neutralization including (1) The concentration of the aqueous zirconium oxychloride solution before performing Step A is 10% by mass or more, and the temperature is 60°C or more and 95°C or less, (2) The concentration of the aqueous ammonia is 10% by mass or more, (3) The volume of the droplets of aqueous ammonia dropped in Step A is 1.0 ml or less, (4) The dropping addition of the aqueous ammonia is carried out in two steps. In the first step, the aqueous ammonia in an amount of 0.9 mol or more and 1.1 mol or less per mol of Zr in terms of NH3 is dropwise added, and then held for 10 minutes or more and 120 minutes or less. (5) In the second step, after further dropwise adding the aqueous ammonia, it is held for 10 minutes or more and 240 minutes or less. (6) During the dropping addition of the aqueous ammonia and during the holding, the temperature of the zirconium oxychloride aqueous solution is maintained within the range of ±5°C of the temperature at the start of dropping. The method for producing the zirconia sol according to any one of [1] to [4] above.

[0016] According to the configuration of [5] above, in step A of neutralization, aqueous ammonia in a specific concentration range with the droplet volume controlled within a specific range is dropwise added to an aqueous zirconium oxychloride solution in a specific concentration range. Specifically, aqueous ammonia with a concentration of 10% by mass or more is dropwise added to an aqueous zirconium oxychloride solution with a concentration of 10% by mass or more. And the droplet volume of the aqueous ammonia to be dropwise added is 1.0 ml or less. Thereby, the zirconia sol of [1] above, that is, the zirconia sol in which the crystallite diameter A is 5.0 nm or more and 50.0 nm or less, the crystallite diameter B is 5.0 nm or more and 50.0 nm or less, and the crystallite diameter ratio X is 0.5 or more and 0.95 or less can be obtained.

[0017] Also, the temperature of the aqueous zirconium oxychloride solution before performing step A is 60°C or more and 95°C or less. The temperature mainly affects the crystallite diameter. The crystallite diameter A on the monoclinic (-111) plane and the crystallite diameter B on the monoclinic (111) plane become larger as the temperature is higher. Since the temperature is 60°C or more, the crystallite diameter A can be 5.0 nm or more, and the crystallite diameter B can be 5.0 nm or more.

[0018] In particular, the dropping addition of the aqueous ammonia is carried out in two steps. In the first stage, the aqueous ammonia is added dropwise in an amount of 0.9 mol or more and 1.1 mol or less per mol of Zr in terms of NH₃, and then held for 10 minutes or more and 120 minutes or less. The holding time after the dropwise addition of the aqueous ammonia in the first stage mainly affects the crystallite size ratio X. The longer the holding time, the smaller the crystallite size ratio X can be. That is, by setting the holding time to 10 minutes or more, the crystallite size ratio X can be set to 0.95 or less. Also, even if the holding time is made longer than 120 minutes, the crystallite size ratio X cannot be reduced more than when held for 120 minutes. Therefore, from the viewpoint of productivity, the holding time is 120 minutes or less.

[0019] Further, during the dropwise addition of the aqueous ammonia and during the holding, the temperature of the zirconium oxychloride aqueous solution is maintained within the range of ±5°C from the temperature at the start of the dropwise addition. The temperature mainly affects the crystallite size. The crystallite size A on the monoclinic (-111) plane and the crystallite size B on the monoclinic (111) plane increase as the temperature is higher. Since the temperature is 60°C or higher, the crystallite size A can be 5.0 nm or more and the crystallite size B can be 5.0 nm or more.

[0020] Thus, according to the configuration of [5] above, by using zirconium hydroxide obtained by controlling the above (1) to the above (6) as a raw material, many particles with a distorted shape can be obtained. That is, a zirconia sol can be obtained in which the crystallite size A is 5.0 nm or more and 50.0 nm or less, the crystallite size B is 5.0 nm or more and 50.0 nm or less, and the crystallite size ratio X is 0.5 or more and 0.95 or less.

[0021] Furthermore, the present invention provides the following. [6] The method for producing a zirconia sol according to [5] above, wherein the holding time in the second stage is 30 minutes or more and 240 minutes or less.

[0022] The retention time after the addition of ammonia water droplets in the second stage mainly affects the crystallite size ratio Y. The longer the retention time, the more the content of the tetragonal phase can be increased. Also, the longer the retention time, the smaller the crystallite size ratio Y can be. That is, by setting the retention time to 30 minutes or more, the crystallite size ratio Y can be set to 1.2 or less. Further, even if the retention time is made longer than 240 minutes, the crystallite size ratio Y cannot be reduced more than that in the case of holding for 240 minutes. Therefore, from the viewpoint of productivity, the retention time is 240 minutes or less.

Advantages of the Invention

[0023] According to the present invention, a more suitable zirconia sol as an abrasive grain can be provided. Also, a method for producing the zirconia sol can be provided.

Brief Description of the Drawings

[0024]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0025] Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited only to these embodiments. In this specification, zirconia (zirconium oxide) is a general one and contains an impurity metal compound of 10% by mass or less including hafnia. Also, in this specification, the expressions "containing" and "comprising" include the concepts of "containing", "comprising", "substantially consisting of", and "consisting only of".

[0026] [Zirconia Sol] Hereinafter, an example of the zirconia sol according to this embodiment will be described. However, the zirconia sol of the present invention is not limited to the following examples.

[0027] The zirconia sol according to this embodiment has a crystallite size A on the monoclinic (-111) plane of 5.0 nm or more and 50.0 nm or less, has a crystallite size B on the monoclinic (111) plane of 5.0 nm or more and 50.0 nm or less, and a crystallite size ratio X represented by the following formula 1 is 0.5 or more and 0.95 or less. <Formula 1> [Crystallite size ratio X] = [Crystallite size A on the monoclinic (-111) plane] / [Crystallite size B on the monoclinic (111) plane] However, the crystallite size A and the crystallite size B are values calculated from powder X-ray diffraction measurement and analysis of the measurement.

[0028] Since the crystallite size A is 5.0 nm or more and the crystallite size B is 5.0 nm or more, it is possible to suppress burial in the polishing pad and maintain a high polishing rate. Also, since the crystallite size A is 50.0 nm or less and the crystallite size B is 50.0 nm or less, the intrusion resistance into the polished surface and the pad interface can be reduced. Since the intrusion resistance can be reduced, the instantaneous pressure applied to the contact point can be reduced. As a result, the polishing rate can be maintained high and the surface roughness can be reduced.

[0029] The crystallite size A is preferably 7.0 nm or more, more preferably 9.0 nm or more. The crystallite size A is preferably 40.0 nm or less, more preferably 35.0 nm or less. The crystallite size A is preferably 7.0 nm or more and 40.0 nm or less, more preferably 9.0 nm or more and 35.0 nm or less.

[0030] The crystallite size B is preferably 7.0 nm or more, more preferably 9.0 nm or more. The crystallite diameter B is preferably 40.0 nm or less, more preferably 35.0 nm or less. The crystallite diameter B is preferably 7.0 nm or more and 40.0 nm or less, more preferably 9.0 nm or more and 35.0 nm or less.

[0031] As described above, the crystallite diameter ratio X is 0.5 or more and 0.95 or less. When the crystallite diameter ratio X is 0.95 or less, the polishing rate can be maintained high. The inventors of the present invention speculate as follows about the reason. When the crystallite diameter ratio X is 0.95 or less, the monoclinic crystal becomes a rectangular parallelepiped or rod shape with a larger aspect ratio. The rectangular parallelepiped and rod-shaped crystals are more difficult to rotate compared to spherical crystals (crystals with a crystallite diameter ratio X of 1). As a result, the frictional resistance with the surface to be polished increases, and the effect of improving the polishing rate is exhibited.

[0032] The crystallite diameter ratio X is preferably 0.55 or more, more preferably 0.58 or more. The crystallite diameter ratio X is preferably 0.9 or less, more preferably 0.87 or less. The crystallite diameter ratio X is preferably 0.55 or more and 0.9 or less, more preferably 0.58 or more and 0.87 or less.

[0033] From the above, the zirconia sol in which the crystallite diameter A is 5.0 nm or more and 50.0 nm or less, the crystallite diameter B is 5.0 nm or more and 50.0 nm or less, and the crystallite diameter ratio X is 0.5 or more and 0.95 or less can be expected to have a higher rate and higher smoothness (low surface roughness) than existing products in precision polishing of semiconductors and the like. In particular, in polishing of SiC or the like with high hardness, a higher rate and higher smoothness (low surface roughness) can be expected than existing products.

[0034] The zirconia sol preferably contains a tetragonal phase in a volume fraction of 2.0% or more and 90.0% or less. When the content of the cubic phase is 2.0% or more and 90.0% or less in terms of volume fraction, it is possible to make the surface roughness of the surface to be polished smaller while maintaining a high polishing rate. Regarding the reason, the present inventors have the following speculation. The cubic phase has the property of undergoing a phase transition to the monoclinic phase under pressure, and is accompanied by a volume expansion of several percent when undergoing the phase transition to the monoclinic phase. Therefore, when the zirconia sol is exposed to pressure at the interface between the pad and the surface to be polished, a part of the cubic phase undergoes a phase transition to the monoclinic phase, and the volume expansion at that time causes the aggregation of crystallites to crack and the aggregation to loosen. As a result, the exposure pressure is relaxed. As a result, since it occurs intermittently during polishing, the instantaneous pressure applied to the surface to be polished by the abrasive grains is suppressed, and the surface roughness can be reduced.

[0035] The content of the cubic phase is more preferably 5.0% or more, and still more preferably 8.0% or more. The content of the cubic phase is more preferably 85.0% or less, and still more preferably 80.0% or less. The content of the cubic phase is more preferably 5.0% or more and 85.0% or less, and still more preferably 8.0% or more and 80.0% or less. The cubic phase does not necessarily have to be contained, but when the cubic phase is present, the surface roughness of the surface to be polished can be further reduced.

[0036] The zirconia sol preferably has a crystallite size ratio Y represented by the following formula 2 of 0.3 or more and 1.2 or less. <Formula 2> [Crystallite size ratio Y]=[Crystallite size A on the monoclinic (-111) plane] / [Crystallite size C on the cubic (101) plane] However, the crystallite size C is a value calculated from powder X-ray diffraction measurement and analysis of the measurement.

[0037] When the crystallite size ratio Y is 0.3 or more and 1.2 or less, the surface roughness of the surface to be polished can be made smaller. Regarding the reason, the present inventors have the following speculation. When the crystallite diameter ratio Y is 0.3 or more and 1.2 or less, the phase transition is likely to be induced. That is, the instantaneous overpressure is more suppressed. As a result, the surface roughness becomes smaller.

[0038] The crystallite diameter ratio Y is more preferably 0.4 or more, and even more preferably 0.5 or more. The crystallite diameter ratio Y is more preferably 1.1 or less, and even more preferably 1.0 or less. The crystallite diameter ratio Y is more preferably 0.4 or more and 1.1 or less, and even more preferably 0.5 or more and 1.0 or less.

[0039] The zirconia sol has a particle diameter D 50 in the range of 5 nm or more and less than 50 nm, and it is preferable that the ratio X obtained by the following procedure is 40% or more. <Procedure> Obtain a transmission electron microscope image containing 20 or more isolated particles. For each isolated particle in the transmission electron microscope image, perform the following operations 1) to 5). 1) Obtain a circumscribed circle and an inscribed circle having the same center as the circumscribed circle. 2) Obtain the ratio [(diameter of the circumscribed circle) / (diameter of the inscribed circle)] of the obtained diameter of the circumscribed circle and the diameter of the inscribed circle. 3) For all isolated particles in the transmission electron microscope image, obtain the ratio [(diameter of the circumscribed circle) / (diameter of the inscribed circle)]. 4) Count the number of isolated particles A for which the ratio [(diameter of the circumscribed circle) / (diameter of the inscribed circle)] is 2.0 or more. 5) Obtain the ratio X of the isolated particles A to all isolated particles. (Ratio X (%)) = [(number of isolated particles A) / (total number of isolated particles)] × 100

[0040] The particle diameter D 50 is preferably 45 nm or less, and more preferably 40 nm or less. The particle diameter D 50 is preferably 7 nm or more, and more preferably 9 nm or more. The particle diameter D 50 is preferably 7 nm or more and 45 nm or less, more preferably 9 nm or more and 40 nm or less. The method for measuring the particle diameter D 50 is, in more detail, the method described in the examples.

[0041] The ratio X is preferably 50% or more, more preferably 55% or more, and even more preferably 60% or more. Although the larger the ratio X is, the more preferable it is, for example, it is 99% or less, 90% or less, etc. The ratio X is preferably 50% or more and 99% or less, more preferably 55% or more and 90% or less, and even more preferably 60% or more and 85% or less. The ratio X is, in more detail, a value obtained by the method described in the examples.

[0042] Particles with the ratio [(diameter of the circumscribed circle) / (diameter of the inscribed circle)] of 2.0 or more can be said to be more angular and distorted-shaped particles. A zirconia sol having such particles is more useful as an abrasive grain.

[0043] The concentration of the zirconia sol is not particularly limited, but is usually 1% by mass or more and 60% by mass or less in terms of ZrO2. When the concentration of the zirconia sol is 1% by mass or more, it is possible to prevent the zirconia concentration from decreasing when diluted with other solvents. When the concentration of the zirconia sol is 60% by mass or less, thickening of the sol is suppressed and the stability is excellent. The concentration of the zirconia sol is more preferably 5% by mass or more, and even more preferably 10% by mass or more. The concentration of the zirconia sol is more preferably 50% by mass or less, and even more preferably 45% by mass or less. The concentration of the zirconia sol is more preferably 5% by mass or more and 50% by mass or less, and even more preferably 10% by mass or more and 45% by mass or less.

[0044] The dispersion medium of the zirconia sol is not particularly limited, and examples thereof include water, hydrophilic organic solvents such as methanol, ethanol, 2-propanol, acetone, and ether, and mixtures of one or more of the hydrophilic organic solvents. The dispersion medium of the zirconia sol is preferably water (pure water or ion-exchanged water) usually.

[0045] The pH of the dispersion medium of the zirconia sol is not particularly limited, but is preferably 1 or more and 13 or less, and more preferably 2 or more and 12 or less. When it contains an acid such as nitric acid, it is more preferably 7 or less, or 1 or more and 6 or less. When the pH of the dispersion medium of the zirconia sol is 7 or less, the pH is away from the isoelectric point of zirconia, and the stability is improved.

[0046] In this specification, the zirconia sol refers to one that does not contain additives such as potassium permanganate for imparting the function as an abrasive. That is, in this specification, the polishing dispersion liquid refers to one containing the zirconia sol and an additive for imparting the function as an abrasive, and in the case of only the zirconia sol, it cannot be a polishing dispersion liquid.

[0047] <Polishing performance> When polishing is performed under the following polishing conditions using the following polishing dispersion liquid, the zirconia sol preferably has a polishing rate of 0.5 μm / hour or more and the surface roughness Ra of the surface to be polished is 1.0 Å or less. When the polishing rate is 0.5 μm / hour or more and the surface roughness Ra of the surface to be polished is 1.0 Å or less, a polished surface with a low surface roughness can be obtained in a short time.

[0048] 1. Preparation of a polishing dispersion liquid for polishing performance evaluation Ion-exchanged water and potassium permanganate are mixed with the zirconia sol to prepare a polishing dispersion liquid containing 15.0% by mass of zirconia in terms of ZrO2 and 1.2% by mass of potassium permanganate. 2. Polishing conditions Substrate (object to be polished): 4H-SiC wafer, 4 inches, Si face, Off 4 degrees, non-doped (surface roughness Ra: 1 Å) Polishing apparatus: Single-sided polishing apparatus (EJ-380N manufactured by ENGIS) Polishing pad: SUBA600 (Nitta DuPont) Polishing load: 280 g / cm 2 Rotational speed of the platen: 80 rpm (linear speed: 9.5 m / min) Polishing time: 2 hours Supply rate of the polishing composition: 10 mL / min Measured area of the object to be polished: 5.0 μm × 5.0 μm (measurement of surface roughness)

[0049] The polishing rate is more preferably 0.6 μm / hour or more, and even more preferably 0.7 μm / hour or more. As long as the surface roughness does not exceed a certain level, the higher the polishing rate, the better. Specifically, the polishing rate is more preferably 5 μm / hour or less, and even more preferably 3 μm / hour or less. The polishing rate is more preferably 0.6 μm / hour or more and 5 μm / hour or less, and even more preferably 0.7 μm / hour or more and 3 μm / hour or less.

[0050] The surface roughness Ra of the surface to be polished is more preferably 0.9 Å or less, and even more preferably 0.8 Å or less. The surface roughness Ra of the surface to be polished is preferably as small as possible. For example, it is 0.1 Å or more, 0.2 Å or more, etc. The surface roughness Ra of the surface to be polished is more preferably 0.1 Å or more and 0.9 Å or less, and even more preferably 0.2 Å or more and 0.8 Å or less.

[0051] The zirconia sol according to this embodiment can be obtained, for example, by the following method for producing zirconia sol.

[0052] [Method for Producing Zirconia Sol] Hereinafter, an example of the method for producing zirconia sol will be described. However, the method for producing zirconia sol is not limited to the following examples.

[0053] The method for producing a zirconia sol according to this embodiment is as follows: Step A of adding and dropping aqueous ammonia to an aqueous zirconium oxychloride solution for neutralization and includes (1) The concentration of the aqueous zirconium oxychloride solution before performing Step A is 10% by mass or more, and the temperature is 60°C or more and 95°C or less. (2) The concentration of the aqueous ammonia is 10% by mass or more. (3) The volume of the droplets of the aqueous ammonia dropped in Step A is 1.0 ml or less. (4) The dropping addition of the aqueous ammonia is performed in two steps. In the first step, the aqueous ammonia of 0.9 mol or more and 1.1 mol or less per mol of Zr in terms of NH3 is dropped and added, and then held for 10 minutes or more and 120 minutes or less. (5) In the second step, after further dropping and adding the aqueous ammonia, it is held for 10 minutes or more and 120 minutes or less. (6) During the dropping addition of the aqueous ammonia and during the holding, the temperature of the aqueous zirconium oxychloride solution is maintained within the range of ±5°C from the temperature at the start of dropping.

[0054] <Step A> First, in Step A, aqueous ammonia is dropped and added to an aqueous zirconium oxychloride solution for neutralization.

[0055] In this embodiment, aqueous ammonia is used as a neutralizing agent for zirconium oxychloride. The concentration of the aqueous ammonia is 10% by mass or more. The concentration of the aqueous ammonia is preferably 15% by mass or more, more preferably 20% by mass or more. The concentration of the aqueous ammonia has no particular upper limit, but is, for example, 30% by mass or less, 28% by mass or less, etc. The concentration of the aqueous ammonia is preferably 15% by mass or more and 30% by mass or less, more preferably 20% by mass or more and 28% by mass or less.

[0056] The concentration of the zirconium oxychloride aqueous solution before performing the step A is 10% by mass or more. The concentration of the zirconium oxychloride aqueous solution is preferably 15% by mass or more, more preferably 18% by mass or more. The concentration of the zirconium oxychloride aqueous solution has no particular upper limit, but is, for example, 28% by mass or less, 25% by mass or less, etc. The concentration of the zirconium oxychloride aqueous solution is preferably 15% by mass or more and 28% by mass or less, more preferably 18% by mass or more and 25% by mass or less.

[0057] The temperature of the zirconium oxychloride aqueous solution before performing the step A is 60°C or more and 95°C or less. The temperature mainly affects the crystallite size. The crystallite size A on the monoclinic (-111) plane and the crystallite size B on the monoclinic (111) plane increase as the temperature is higher. Since the temperature is 60°C or more, the crystallite size A can be 5.0 nm or more, and the crystallite size B can be 5.0 nm or more.

[0058] The temperature of the zirconium oxychloride aqueous solution before performing the step A is preferably 65°C or more. The temperature of the zirconium oxychloride aqueous solution before performing the step A is preferably 90°C or less. The temperature of the zirconium oxychloride aqueous solution before performing the step A is preferably 65°C or more and 90°C or less.

[0059] The volume of the droplets of aqueous ammonia dropped in the step A is 1.0 ml or less. The volume of the droplets is preferably 0.7 ml or less, more preferably 0.5 ml or less. The smaller the volume of the droplets, the more preferable, but is, for example, 0.05 ml or more, 0.1 ml or more, etc. The volume of the droplets is preferably 0.05 ml or more and 0.7 ml or less, more preferably 0.1 ml or more and 0.5 ml or less.

[0060] The dropwise addition of the aqueous ammonia is performed in two steps. In the first stage, the aqueous ammonia is added dropwise in an amount of 0.9 mol or more and 1.1 mol or less per mol of Zr in terms of NH₃, and then held for 10 minutes or more and 120 minutes or less. The holding time after the addition of the aqueous ammonia in the first stage mainly affects the crystallite size ratio X. The longer the holding time, the smaller the crystallite size ratio X can be. That is, by setting the holding time to 10 minutes or more, the crystallite size ratio X can be set to 0.95 or less. Also, even if the holding time is made longer than 120 minutes, the crystallite size ratio X cannot be reduced more than when held for 120 minutes. Therefore, from the viewpoint of productivity, the holding time is 120 minutes or less.

[0061] The dropping time of the aqueous ammonia is not particularly limited. For example, when 1000 ml of aqueous ammonia is added dropwise to 1000 ml of an aqueous zirconium oxychloride solution, it is preferably 10 minutes or more and 120 minutes or less. The dropping time is more preferably 90 minutes or less, and even more preferably 60 minutes or less.

[0062] The holding time (holding time in the first stage) is preferably 20 minutes or more, and more preferably 30 minutes or more. The holding time is preferably 100 minutes or less, and more preferably 90 minutes or less. The holding time is preferably 20 minutes or more and 100 minutes or less, and more preferably 30 minutes or more and 90 minutes or less.

[0063] In the second stage, further, after the aqueous ammonia is added dropwise, it is held for 10 minutes or more and 240 minutes or less.

[0064] The amount of the aqueous ammonia added dropwise in the second stage is not limited, but is 1 mol or more and 15 mol or less, preferably 2 mol or more and 10 mol or less per mol of Zr in terms of NH₃.

[0065] The dropping time of aqueous ammonia in the second stage is not particularly limited. For example, when 1000 ml of aqueous ammonia is dropwise added to 1000 ml of an aqueous zirconium oxychloride solution, it is preferably 10 minutes or more and 120 minutes or less. The dropping time is more preferably 90 minutes or less, and even more preferably 60 minutes or less.

[0066] The holding time (the holding time after the dropwise addition of aqueous ammonia in the second stage) is preferably 30 minutes or more, and more preferably 60 minutes or more. The holding time is preferably 180 minutes or less, and more preferably 150 minutes or less. The holding time is preferably 30 minutes or more and 180 minutes or less, and more preferably 60 minutes or more and 150 minutes or less.

[0067] The holding time (the holding time after the dropwise addition of aqueous ammonia in the second stage) mainly affects the crystallite size ratio Y. The longer the holding time, the more the content of the tetragonal phase can be increased. The longer the holding time, the smaller the crystallite size ratio Y can be. That is, by setting the holding time to 30 minutes or more, the crystallite size ratio Y can be made 1.2 or less. Also, even if the holding time is made longer than 240 minutes, the crystallite size ratio Y cannot be reduced more than that in the case of holding for 240 minutes. Therefore, from the viewpoint of productivity, the holding time is 120 minutes or less. In addition, when the holding time is less than 30 minutes, there may be no tetragonal phase. However, even when there is no tetragonal phase, if the crystallite size ratio X is 0.5 or more and 0.95 or less, it is acceptable. That is, if the crystallite size ratio X is 0.5 or more and 0.95 or less, even when the crystallite size ratio Y does not satisfy 0.3 or more and 1.2 or less, the polishing dispersion prepared using the zirconia sol can maintain a high polishing rate and can reduce the surface roughness of the surface to be polished.

[0068] During the dropping addition of the aqueous ammonia and during the holding, the temperature of the zirconium oxychloride aqueous solution is maintained within the range of ±5°C from the temperature at the start of dropping. The temperature mainly affects the crystallite size. The crystallite size A on the monoclinic (-111) plane and the crystallite size B on the monoclinic (111) plane increase as the temperature gets higher. Since the temperature is 60°C or higher, the crystallite size A can be 5.0 nm or more, and the crystallite size B can be 5.0 nm or more.

[0069] According to the method for producing the zirconia sol, by using zirconium hydroxide obtained by controlling the above (1) to the above (6) as a raw material, many particles with a distorted shape can be obtained. That is, a zirconia sol can be obtained in which the crystallite size A is 5.0 nm or more and 50.0 nm or less, the crystallite size B is 5.0 nm or more and 50.0 nm or less, and the crystallite size ratio X is 0.5 or more and 0.95 or less. Also, the ratio X can be easily made 40% or more.

[0070] After the step A, if necessary, stirring is performed to homogenize. Thereby, a precipitate of zirconium hydroxide is obtained. The time for the stirring is not particularly limited, and for example, it is 15 minutes or more and 120 minutes or less.

[0071] Thereafter, if necessary, the zirconium hydroxide is washed. The washing is performed, for example, until the Cl concentration becomes a predetermined concentration or less. As the predetermined concentration, for example, 0.01% or less is preferable. The washing method is not particularly limited, and examples thereof include a method of repeatedly performing an operation of filtering zirconium hydroxide and dispersing it in ion-exchanged water.

[0072] <Step B> After the step A, the zirconium hydroxide obtained in the step A is heated and aged under acidic conditions. To make it acidic, usually an acid is added as a peptizing agent to the zirconium hydroxide. Water may be added as necessary to adjust the concentration. The concentration is not particularly limited, but preferably 1% by mass or more and 30% by mass or less in terms of ZrO2, and more preferably 5% by mass or more and 20% by mass or less.

[0073] As the peptizing agent for zirconium hydroxide, there is no particular limitation as long as it is a water-soluble inorganic acid or organic acid. Examples include hydrochloric acid, nitric acid, sulfuric acid, acetic acid, lactic acid, citric acid, tartaric acid, malic acid, mandelic acid, etc. However, hydrochloric acid and nitric acid are preferred because even if they are present in excess in the zirconia sol, they can be easily removed by purification with water after the formation of the zirconia sol. The addition amount of the peptizing agent is such that acid / ZrO2 (molar ratio) = 0.01 or more and 3 or less, more preferably 0.1 or more and 1.5 or less. When the acid / ZrO2 (molar ratio) is 0.01 or more, the peptization of zirconium hydroxide can be made sufficient. Also, since the quantitative effect is small even when the acid / ZrO2 (molar ratio) exceeds 3, it is economical when the acid / ZrO2 (molar ratio) is 3 or less.

[0074] Next, in order to change the zirconium hydroxide to zirconium oxide simultaneously with peptization, heating and aging are carried out. From the viewpoint of yield, the heating and aging temperature is preferably 70 °C or higher, more preferably 80 °C or higher. The heating temperature is preferably 200 °C or lower, more preferably 180 °C or lower. The heating temperature is preferably 70 °C or higher and 200 °C or lower, more preferably 80 °C or higher and 180 °C or lower. When the aging temperature is 70 °C or higher, the progress of the peptization reaction becomes suitable. Also, when the aging temperature is 200 °C or lower, the aggregation does not become too strong and the dispersibility is good. From the viewpoint of yield, the heating and aging time is preferably 24 hours or more, more preferably 48 hours or more. The heating and aging time is preferably 120 hours or less, more preferably 100 hours or less. The heating and aging time is preferably 24 hours or more and 120 hours or less, more preferably 48 hours or more and 100 hours or less.

[0075] After that, after cooling to room temperature, ultrafiltration may be carried out to concentrate the zirconia sol. The acid added in excess can be easily removed using ultrafiltration.

[0076] The manufacturing method of the zirconia sol according to the present embodiment has been described above.

Examples

[0077] Hereinafter, the present invention will be described in detail using examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded. In the zirconia sols in the examples and comparative examples, hafnium is contained in an amount of 1 to 3% by mass with respect to zirconium as an inevitable impurity (calculated by the following formula (X)). <Formula (X)> ([Mass of hafnium oxide] / ([Mass of zirconium oxide]+[Mass of hafnium oxide]))×100 (%)

[0078] The maximum and minimum values of the contents of the respective components shown in the following examples should be considered as the preferable minimum and maximum values of the present invention regardless of the contents of the other components. Also, the maximum and minimum values of the measured values shown in the following examples should be considered as the preferable minimum and maximum values of the present invention regardless of the contents (compositions) of the respective components.

[0079] [Preparation of Zirconia Sol] (Example 1) As a first step, 138 g of aqueous ammonia (10% by mass) adjusted to 25°C was added dropwise to 1000 g of an aqueous zirconium oxychloride solution (10% by mass in terms of ZrO₂) adjusted to 60°C with a mantle heater over 10 minutes. At this time, the number of liquid delivery pipes and the dropping rate were adjusted so that the volume of the liquid droplets of aqueous ammonia was in the range of 0.1 to 0.5 ml. Thereafter, stirring was continued for 60 minutes. Then, as a second step, 1242 g of aqueous ammonia (10% by mass) adjusted to 25°C was added dropwise over 30 minutes. Also in the second step, the number of liquid delivery pipes and the dropping rate were adjusted so that the volume of the liquid droplets of aqueous ammonia was in the range of 0.1 to 0.5 ml. Thereafter, stirring was continued for 10 minutes to obtain a precipitate of zirconium hydroxide. During the dropping of aqueous ammonia and during the stirring after dropping, the aqueous zirconium oxychloride solution was adjusted to maintain within ±5°C of the initial temperature. The washing operation of filtering off zirconium hydroxide and dispersing it again in ion-exchanged water was repeated until the Cl concentration reached 0.01% or less. The concentration of zirconium hydroxide after washing was 24.0% by mass in terms of ZrO₂. To 416 g of the obtained zirconium hydroxide, 556 g of ion-exchanged water and 28.0 g of nitric acid (60% by mass) were mixed, and the prepared slurry was placed in a separable flask and held at 100°C under reflux for 120 hours while stirring. The obtained zirconia sol precursor was purified using ultrafiltration to obtain the zirconia sol according to Example 1. The ZrO₂ concentration of the sol was 20% by mass, the pH was 3.3, and the particle size D 50 was 51 nm.

[0080] (Example 2) Zirconium hydroxide was obtained in the same manner as in Example 1 except that 1000 g of an aqueous zirconium oxychloride solution (10% by mass in terms of ZrO₂) adjusted to 75°C with a mantle heater was used. The concentration of zirconium hydroxide after washing was 22.8% by mass in terms of ZrO₂. A zirconia sol was obtained in the same manner as in Example 1 except that 533 g of ion-exchanged water and 28.0 g of nitric acid (60% by mass) were mixed with 439 g of the obtained zirconium hydroxide. The ZrO₂ concentration of the sol was 20% by mass, the pH was 3.1, and the particle size D 50 was 73 nm.

[0081] (Example 3) Zirconium hydroxide was obtained in the same manner as in Example 1, except that 1000 g of an aqueous zirconium oxychloride solution (10% by mass in terms of ZrO2) adjusted to 90 °C with a mantle heater was used. The concentration of zirconium hydroxide after washing was 21.3% by mass in terms of ZrO2. A zirconia sol was obtained in the same manner as in Example 1, except that 503 g of ion-exchanged water and 28.0 g of nitric acid (60% by mass) were mixed with 469 g of the obtained zirconium hydroxide. The ZrO2 concentration of the sol was 20% by mass, the pH was 3.4, and the particle size D 50 was 95 nm.

[0082] (Example 4) Zirconium hydroxide was obtained in the same manner as in Example 1, except that 1000 g of an aqueous zirconium oxychloride solution (10% by mass in terms of ZrO2) adjusted to 75 °C with a mantle heater was used, and 138 g of aqueous ammonia (10% by mass) adjusted to 25 °C was added dropwise over 10 minutes as the first step, followed by continuing stirring for 90 minutes. The concentration of zirconium hydroxide after washing was 22.9% by mass in terms of ZrO2. A zirconia sol was obtained in the same manner as in Example 1, except that 535 g of ion-exchanged water and 28.0 g of nitric acid (60% by mass) were mixed with 437 g of the obtained zirconium hydroxide. The ZrO2 concentration of the sol was 20% by mass, the pH was 3.1, and the particle size D 50 was 44 nm.

[0083] (Example 5) Zirconium hydroxide was obtained in the same manner as in Example 1, except that 1000 g of an aqueous zirconium oxychloride solution (10% by mass in terms of ZrO2) adjusted to 75 °C with a mantle heater was used, and 1242 g of aqueous ammonia (10% by mass) adjusted to 25 °C was added dropwise over 30 minutes as the second step, followed by continuing stirring for 30 minutes. The concentration of zirconium hydroxide after washing was 23.8% by mass in terms of ZrO₂. A zirconia sol was obtained in the same manner as in Example 1 except that 535 g of ion-exchanged water and 28.0 g of nitric acid (60% by mass) were mixed with 420 g of the obtained zirconium hydroxide. The ZrO₂ concentration of the sol was 20% by mass, the pH was 3.3, and the particle size D 50 was 43 nm.

[0084] (Example 6) 1000 g of an aqueous zirconium oxychloride solution (10% by mass in terms of ZrO₂) adjusted to 75 °C with a mantle heater was used. As the second step, 1242 g of aqueous ammonia (10% by mass) adjusted to 25 °C was added dropwise over 30 minutes, and then stirring was continued for 60 minutes. Zirconium hydroxide was obtained in the same manner as in Example 1. The concentration of zirconium hydroxide after washing was 23.2% by mass in terms of ZrO₂. A zirconia sol was obtained in the same manner as in Example 1 except that 541 g of ion-exchanged water and 28.0 g of nitric acid (60% by mass) were mixed with 431 g of the obtained zirconium hydroxide. The ZrO₂ concentration of the sol was 20% by mass, the pH was 3.2, and the particle size D 50 was 39 nm.

[0085] (Example 7) 1000 g of an aqueous zirconium oxychloride solution (10% by mass in terms of ZrO₂) adjusted to 75 °C with a mantle heater was used. As the second step, 1242 g of aqueous ammonia (10% by mass) adjusted to 25 °C was added dropwise over 30 minutes, and then stirring was continued for 120 minutes. Zirconium hydroxide was obtained in the same manner as in Example 1. The concentration of zirconium hydroxide after washing was 22.6% by mass in terms of ZrO₂. A zirconia sol was obtained in the same manner as in Example 1 except that 530 g of ion-exchanged water and 28.0 g of nitric acid (60% by mass) were mixed with 442 g of the obtained zirconium hydroxide. The ZrO₂ concentration of the sol was 20% by mass, the pH was 3.3, and the particle size D 50 was 34 nm.

[0086] (Comparative Example 1) 1380 g of aqueous ammonia (10% by mass) adjusted to 25°C was added dropwise to 1000 g of an aqueous zirconium oxychloride solution (10% by mass in terms of ZrO₂) adjusted to 25°C over 40 minutes. At this time, the number of liquid feed pipes and the dropping rate were adjusted so that the volume of the liquid droplets of aqueous ammonia was in the range of 0.1 to 0.5 ml. Then, stirring was continued for 10 minutes to obtain a precipitate of zirconium hydroxide. The operation of filtering off zirconium hydroxide and redispersing it in ion-exchanged water for washing was repeated until the Cl concentration became 0.01% or less. The concentration of zirconium hydroxide after washing was 28.4% by mass in terms of ZrO₂. A zirconia sol was obtained in the same manner as in Example 1 except that 620 g of ion-exchanged water and 28.0 g of nitric acid (60% by mass) were mixed with 352 g of the obtained zirconium hydroxide. The ZrO₂ concentration of the sol was 20% by mass, the pH was 3.3, and the particle size D 50 was 72 nm.

[0087] (Comparative Example 2) 3000 g of zirconium hydroxide obtained in the same manner as in Example 1 was filled into a corundum sheath and fired in a batch electric furnace at 1150°C for 10 hours to obtain zirconium oxide. A mixture of 600 g of the obtained zirconium oxide, 1400 g of ion-exchanged water, and 5.0 g of nitric acid (60% by mass) was ground in a bead mill using zirconium oxide grinding media with a diameter of 0.3 mm to obtain a zirconia sol. The ZrO₂ concentration of the sol was 20% by mass, the pH was 3.2, and the particle size D 50 was 236 nm.

[0088] [Measurement of particle size D 50 The zirconia sols of the examples and comparative examples were diluted with ion-exchanged water to 1.0% by mass in terms of ZrO₂, put into an apparatus (dynamic light scattering particle size distribution measuring apparatus ("Zetasizer Nano ZS" manufactured by Malvern Panalytical)), and the particle size D 50 (based on volume frequency distribution) of the zirconia sol was measured. The results are shown in Table 1. <Measurement conditions> Measurement temperature: 25°C Scattering angle: 173° Dispersed substance: ZrO2 Dispersion medium: water Cell: genuine disposable cell Number of repetitions: 3 (average value of particle diameter D 50 is the average value for 3 times)

[0089] [Powder X-ray diffraction measurement and analysis] The 100 °C dried products of the zirconia sols obtained in the examples and comparative examples were measured with an X-ray diffractometer ("RINT2500" manufactured by Rigaku) to obtain X-ray diffraction charts. The measurement conditions were as follows. The X-ray diffraction chart of Example 1 is shown in Fig. 1, and the X-ray diffraction chart of Example 5 is shown in Fig. 2. [Measurement conditions] Measuring device: X-ray diffractometer (manufactured by Rigaku, RINT2500) X-ray source: CuKα X-ray source Tube voltage: 50 kV Tube current: 300 mA Scanning angle: 2θ = 10 to 50° Scanning speed: 1° / min

[0090] Using Powder XRD, SmartLab Studio II (RIGAKU), the range of 2θ = 20 to 40° of the chart was analyzed to calculate the crystallite size and tetragonal ratio for each crystal plane. The results are shown in Table 1. Table 1 also shows the crystallite size ratio X ([crystallite size A on the monoclinic (-111) plane] / [crystallite size B on the monoclinic (111) plane]) and the crystallite size ratio Y ([crystallite size A on the monoclinic (-111) plane] / [crystallite size C on the tetragonal (101) plane]). For this calculation, three peaks with peak tops located in the ranges of 27.5 - 28.5°, 29.5 - 30.5°, and 31.0 - 32.0° of the diffraction chart were targeted. 27.5 - 28.5° is attributed to m(-111), 29.5 - 30.5° is attributed to t(101) or c(111), and 31.0 - 32.0° is attributed to m(111). Even if the peak angle deviates from the above ranges or the peak splits due to the change in lattice constant caused by the solid solution of other elements in zirconia, if it is reasonable to attribute it to the above crystal planes, it was used for this analysis. In this specification, it is not always necessary to distinguish between t(101) and c(111), and they are treated as the same. In addition, the following operations and conditions were used for the analysis. After loading the powder X-ray diffraction measurement data in the software Powder XRD in SmartLab Studio II, peak processing is executed. The peak profiling conditions are set as follows. Peak search: Check box ON Pretreatment: Customize Method: Second derivative method σ cut-off value: 3 (Adjust between 0.5 - 3 if no clearly visible peaks are detected) Profile fitting: Check box ON Peak shape: Split pseudo-Voigt function Background type: B-spline Fitting conditions: Automatic Refine background: Check box ON For the calculation of crystallite size and crystallite size ratio, the values displayed in the column of crystallite size (Å) shown in the peak list tab (( )-written values are ignored) are used. For the calculation of the tetragonal ratio, the values displayed in the column of integrated intensity (count°) shown in the peak list tab (( )-written values are ignored) are used.

[0091] The tetragonal ratio was calculated from the following formula based on the diffraction peak intensity I of each crystal plane obtained from the above analysis. [Ratio of tetragonal phase (%)] = {It(101) + Ic(111)} / {It(101) + Ic(111) + Im(-111) + Im(111)} × 100 Here, Im(-111) is the diffraction intensity of (-111) of the monoclinic phase, and Im(111) is the diffraction intensity of (111) of the monoclinic phase. It(101) is the diffraction intensity of (101) of the tetragonal phase. Ic(111) is the diffraction intensity of (111) of the cubic phase.

[0092] [Measurement of particle shape] First, TEM images (transmission electron microscope images) of the zirconia sols of the examples and comparative examples were obtained. For imaging the TEM images, a transmission electron microscope (manufactured by Hitachi, Ltd., product name: HV-8100) was used, and the size of one field of view was set to 1.15 μm × 0.90 μm. Next, the number of isolated particles was counted visually. Specifically, the number of particles whose diameter of the circumscribed circle circumscribing the particle was 70% or more of the particle diameter D 50 of the zirconia sol was counted. When there are a plurality of circumscribed circles circumscribing the particle, the one with the minimum ratio of the diameter of the circumscribed circle to the diameter of the inscribed circle (concentric inscribed circle) having the same center as the circumscribed circle (see "2)" below) was adopted. Note that particles with a diameter of the circumscribed circle circumscribing the particle less than 70% of the particle diameter D 50 of the zirconia sol were not counted as the counting target because the effect of such particles as an abrasive is low. When the number of isolated particles was 20 or more, the TEM image was used as the image to be evaluated. When the number of isolated particles was less than 20, a TEM image of another field of view was taken, and the process was repeated until a TEM image with 20 or more isolated particles was obtained. For each isolated particle (isolated particle counted as the target) in the obtained TEM image, the following operations were performed. 1) First, the circumscribed circle of the particle and the inscribed circle (concentric inscribed circle) having the same center as the circumscribed circle were determined (see Figure 3). Note that the definitions of the circumscribed circle and the inscribed circle are the same as the MCC method for circularity in JIS B 7451:1997. 2) Next, the ratio of the diameter of the circumscribed circle to the diameter of the inscribed circle obtained, [(diameter of the circumscribed circle) / (diameter of the inscribed circle)], was determined. 3) For all the isolated particles in the TEM image (all the isolated particles targeted for counting), the ratio [(diameter of the circumscribed circle) / (diameter of the inscribed circle)] was determined. 4) The number of isolated particles with a ratio of [(diameter of the circumscribed circle) / (diameter of the inscribed circle)] of 2.0 or more (hereinafter also referred to as "isolated particle A") was counted. 5) The proportion of isolated particle A relative to all the isolated particles (all the isolated particles targeted for counting) (hereinafter also referred to as "proportion X") was determined. (Proportion X (%)) = [(number of isolated particle A) / (total number of isolated particles)] × 100 The results are shown in Table 1. Note that Fig. 3 is an example of drawing when calculating the proportion X in Example 1. In this example, the diameter of the circumscribed circle was 36.0 nm and the diameter of the inscribed circle was 13.8 nm.

[0093] [Evaluation of Polishing Performance] The zirconia sols of the examples and comparative examples were mixed with ion-exchanged water and potassium permanganate to prepare a polishing dispersion liquid containing 15% by mass in terms of ZrO2 and 1.2% by mass in terms of KMnO4. Using this polishing dispersion liquid, the SiC wafer was polished, and the polishing rate and the surface roughness Ra of the polished surface were measured. The polishing conditions were as follows. Substrate (object to be polished): 4H-SiC wafer, 4 inches, Si face, Off 4 degrees, non-doped (surface roughness Ra: 1 Å) Polishing apparatus: Single-sided polishing apparatus (EJ-380N manufactured by ENGIS) Polishing pad: SUBA600 (Nitta DuPont) Polishing load: 280 g / cm 2 Rotational speed of the platen: 80 rpm (linear speed: 9.5 m / min) Polishing time: 2 hours Supply rate of the polishing composition: 10 mL / min Measured area of the object to be polished: 5.0 μm × 5.0 μm (measurement of surface roughness)

[0094] The method for measuring the polishing rate was calculated from the difference in the weights of the substrate before and after polishing. The surface roughness (arithmetic mean roughness (Ra)) of the polished surface of the object to be polished after polishing was measured using an AFM “Dimension Edge” manufactured by Bruker under the condition that the viewing angle was 5.0 μm × 5.0 μm. The results are shown in Table 1.

[0095]

Table 1

Claims

1. The crystallite size A on the monoclinic (-111) plane is 5.0 nm or more and 50.0 nm or less, The crystallite size B on the monoclinic (111) plane is 5.0 nm or more and 50.0 nm or less, A zirconia sol characterized in that the crystallite diameter ratio X represented by the following formula 1 is 0.5 or more and 0.95 or less. <Formula 1> [Crystallite diameter ratio X] = [Crystallite diameter A on monoclinic (-111) plane] / [Crystallite diameter B on monoclinic (111) plane] Here, the crystallite size A and the crystallite size B are values ​​calculated from powder X-ray diffraction measurement and analysis of the measurement.

2. 2. The zirconia sol according to claim 1, characterized in that it contains a tetragonal phase in a volume fraction of 2.0% to 90.0%.

3. 3. The zirconia sol according to claim 1, wherein the crystallite size ratio Y represented by the following formula 2 is 0.3 or more and 1.2 or less. <Formula 2> [Crystallite diameter ratio Y] = [Crystallite diameter A on monoclinic (-111) plane] / [Crystallite diameter C on tetragonal (101) plane] Here, the crystallite size C is a value calculated from powder X-ray diffraction measurement and analysis of the measurement.

4. Particle diameter D ５０ is in the range of 5 nm or more and less than 50 nm, 3. The zirconia sol according to claim 1, wherein the ratio X obtained by the following procedure is 40% or more. <Procedure> A transmission electron microscope image is obtained that contains 20 or more isolated particles. The following operations 1) to 5) are carried out for each isolated particle in the transmission electron microscope image. 1) Find the circumscribing circle and the inscribing circle that has the same center as the circumscribing circle. 2) The ratio of the diameter of the obtained circumscribing circle to the diameter of the inscribing circle [(diameter of the circumscribing circle) / (diameter of the inscribing circle)] is calculated. 3) For all isolated particles in the transmission electron microscope image, the ratio [(circumscribed circle diameter) / (inscribed circle diameter)] is calculated. 4) The number of isolated particles A having a ratio [(circumscribed circle diameter) / (inscribed circle diameter)] of 2.0 or more is counted. 5) The ratio X of the isolated particles A to all the isolated particles is calculated. (Proportion X (%)) = [(Number of isolated particles A) / (Total number of isolated particles)] × 100

5. Step A: Neutralizing the aqueous zirconium oxychloride solution by dropwise addition of aqueous ammonia Including, (1) The concentration of the aqueous zirconium oxychloride solution before carrying out the step A is 10% by mass or more, and the temperature is 60° C. or more and 95° C. or less; (2) The concentration of the ammonia water is 10% by mass or more, (3) The volume of the droplet of ammonia water dropped in the step A is 1.0 ml or less; (4) The dropwise addition of the ammonia water is carried out in two stages. In the first stage, NH ３ The ammonia water is dropwise added in an amount of 0.9 moles or more and 1.1 moles or less per mole of Zr, and then the mixture is held for 10 minutes or more and 120 minutes or less. (5) In the second stage, after the ammonia water is added dropwise, the mixture is held for 10 minutes or more and 240 minutes or less, (6) The method for producing a zirconia sol according to claim 1 or 2, characterized in that, during the dropwise addition of the ammonia water and during the holding, the temperature of the aqueous zirconium oxychloride solution is maintained within a range of ±5°C of the temperature at the start of the dropwise addition.

6. 6. The method for producing a zirconia sol according to claim 5, wherein the retention time in the second step is from 30 minutes to 240 minutes.

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