Cerium dioxide as well as preparation method and application thereof

Abstract

The invention discloses cerium dioxide and a preparation method and application thereof, and the preparation method of the cerium dioxide comprises the following steps: heating an aqueous solution of tetravalent cerium nitrate, adjusting the pH value of the system, carrying out a precipitation reaction, separating to take a precipitate, adding water and sulfate, carrying out a hydrothermal reaction, and calcining to obtain the cerium dioxide. Wherein the temperature of the hydrothermal reaction is 110 to 200 DEG C. According to the preparation method disclosed by the invention, the cerium dioxide with high Ce < 4 + > / Ce element content and small particle size dispersity is prepared by controlling the temperature of the hydrothermal reaction and using the sulfate.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of inorganic materials, and more particularly to a cerium dioxide, a preparation method and application thereof. BACKGROUND

[0002] STI (Shallow Trench Isolation) is an advanced isolation technology used to isolate transistors (such as MOSFETs) by etching shallow trenches between transistors and filling them with high-density insulating materials (such as silicon dioxide) to achieve electrical isolation. STI polishing is an important step in the semiconductor manufacturing process, mainly used to remove excess filling materials (such as silicon dioxide, silicon nitride, etc.) on the surface of STI structures to achieve planarization and improve surface quality. Cerium dioxide is widely used in the preparation of polishing liquid for STI polishing due to its high chemical activity, which can react with excess filling materials (such as silicon dioxide, silicon nitride, etc.) on the surface of STI structures to accelerate the polishing process. In addition, the hardness of cerium dioxide is slightly lower than that of silicon wafers, which will not cause significant mechanical damage to silicon wafers during polishing, i.e. cerium dioxide can remove excess filling materials on the surface of STI structures while maintaining the integrity and flatness of the surface of silicon wafers, resulting in a relatively smooth and clean plane.

[0003] Cerium dioxide contains both trivalent cerium and tetravalent cerium. Tetravalent cerium has strong oxidizing ability and can react with various materials (such as silicon dioxide, silicon nitride, etc.) to accelerate the polishing process, while trivalent cerium has strong reducing properties, which may cause redox imbalance in the polishing liquid used for STI polishing, thereby affecting the polishing effect of STI polishing. Therefore, in order to improve the polishing effect of the polishing liquid, it is necessary to use cerium dioxide with high Ce 4+ / Ce element content (i.e. the content of tetravalent cerium in cerium elements of cerium dioxide). In addition, cerium dioxide with uniform particle size and small particle size dispersion is beneficial to improve the polishing effect of the polishing liquid.

[0004] Therefore, it is of great significance to develop a preparation method for preparing cerium dioxide with high Ce 4+ / Ce element content and small particle size dispersion. SUMMARY

[0005] The present application aims to solve the problems of the prior art and provide a cerium dioxide, a preparation method and application thereof.

[0006] To achieve the above-mentioned purpose, the technical solution adopted by the present application is as follows:

[0007] In a first aspect, the present application provides a preparation method of cerium dioxide, comprising the following steps:

[0008] The aqueous solution of cerium nitrate is heated, and a precipitation reaction is carried out by adjusting the pH of the system, the precipitate is separated, water and a sulfate salt are added to carry out a hydrothermal reaction, and calcination is carried out, so as to obtain cerium dioxide.

[0009] Preferably, the temperature of the hydrothermal reaction is 110-200℃.

[0010] In the preparation method, by controlling the temperature of the hydrothermal reaction and using a sulfate salt, cerium dioxide with high Ce 4+ / Ce element content and small particle size dispersity can be prepared.

[0011] Specifically, by controlling the temperature of the hydrothermal reaction, the water molecules are converted into high-energy gaseous state, the impact of the gaseous water molecules changes the structure of the cerium precipitate surface, the specific surface area of the cerium precipitate is increased, and the sulfate radical of the sulfate salt is tightly adsorbed on the surface of the cerium precipitate. Not only can it prevent the agglomeration of the subsequently generated cerium dioxide particles, but also can reduce the particle size dispersity of the cerium dioxide, and can also use its own negative charge to bind the oxygen in the cerium dioxide, prevent it from escaping to form oxygen vacancies and increase the Ce 3+ content, thereby facilitating the increase of the Ce 4+ / Ce element content of the cerium dioxide.

[0012] In addition, the reason why the sulfate salt is selected instead of the carbonate salt is that in the system of the present application, the adsorption of the sulfate radical on the surface of the cerium precipitate is much stronger than that of the carbonate radical, and the sulfate radical has stronger ability to prevent the agglomeration of the cerium dioxide particles and to bind the oxygen in the cerium dioxide.

[0013] Preferably, the temperature of the hydrothermal reaction is one of 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃ or a range value between any two of them.

[0014] More preferably, the temperature of the hydrothermal reaction is 120-200℃.

[0015] Further, the temperature of the hydrothermal reaction is 150-200℃.

[0016] Preferably, the ratio of the amount of substance of cerium in the aqueous solution of cerium nitrate to the amount of substance of sulfate radical in the sulfate salt is 1mol:(0.1-0.8)mol.

[0017] More preferably, the ratio of the amount of substance of cerium in the aqueous solution of tetravalent cerium nitrate to the amount of substance of sulfate radical in the sulfate is one of 1 mol:0.1 mol, 1 mol:0.2 mol, 1 mol:0.3 mol, 1 mol:0.4 mol, 1 mol:0.5 mol, 1 mol:0.6 mol, 1 mol:0.7 mol, 1 mol:0.8 mol or a range value between any two of them.

[0018] More preferably, the ratio of the amount of substance of cerium in the aqueous solution of tetravalent cerium nitrate to the amount of substance of sulfate radical in the sulfate is 1 mol:(0.1-0.5) mol.

[0019] More preferably, the ratio of the amount of substance of cerium in the aqueous solution of tetravalent cerium nitrate to the amount of substance of sulfate radical in the sulfate is 1 mol:(0.3-0.5) mol.

[0020] Preferably, the sulfate is at least one of sodium sulfate, potassium sulfate, ammonium sulfate, ammonium bisulfate.

[0021] Preferably, the system has a pH of 6-10.

[0022] More preferably, the system has a pH of one of 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10 or a range value between any two of them.

[0023] More preferably, the system has a pH of 6-8.

[0024] Preferably, the pH adjusting agent for adjusting the system is at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate.

[0025] More preferably, the concentration of the adjusting agent is 0.001-0.1 mol / L, specifically 0.01-0.05 mol / L.

[0026] Preferably, the concentration of the aqueous solution of tetravalent cerium nitrate is 0.01-1.0 mol / L, specifically 0.03-0.6 mol / L.

[0027] More preferably, the concentration of the aqueous solution of tetravalent cerium nitrate is 0.05-0.5 mol / L, further 0.06-0.4 mol / L.

[0028] In the present application, the tetravalent cerium nitrate used in the aqueous solution of tetravalent cerium nitrate can be obtained by commercial purchase or self-preparation. The present application provides a preparation method of tetravalent cerium nitrate, specifically as follows:

[0029] The preparation method of the tetravalent cerium nitrate comprises: mixing a trivalent cerium salt aqueous solution and an alkaline precipitant solution under the condition of an oxidant to react, obtaining a tetravalent cerium hydroxide precipitate, and adding nitric acid to dissolve, thereby obtaining the tetravalent cerium nitrate.

[0030] More preferably, the oxidant is at least one of air, oxygen, and hydrogen peroxide.

[0031] More preferably, the trivalent cerium salt is cerium chloride and / or cerium nitrate.

[0032] More preferably, the concentration of the trivalent cerium salt aqueous solution is 0.1-3 mol / L, and further can be 0.2-2 mol / L.

[0033] More preferably, the alkaline precipitant is at least one of sodium hydroxide and potassium hydroxide.

[0034] More preferably, the concentration of the alkaline precipitant solution is 1-10 mol / L, and further can be 2-8 mol / L.

[0035] More preferably, the solvent of the alkaline precipitant solution is water.

[0036] More preferably, the ratio of the amount of substance of the alkaline precipitant to the amount of substance of the trivalent cerium salt is (2-10):1, and further can be (3-8):1.

[0037] More preferably, the temperature of the reaction is 20-80℃, and further can be 25-65℃.

[0038] More preferably, the time of the reaction is 0.5-10 h, and further can be 1-8 h.

[0039] More preferably, the mass fraction of the nitric acid is 65-68%.

[0040] More preferably, the temperature of the dissolution by adding the nitric acid is 30-100℃, specifically 50-100℃, and further can be 60-100℃.

[0041] Preferably, the temperature of the heating is 60-95℃.

[0042] Preferably, the time of the heating is 0.5-48 h.

[0043] More preferably, the time of the heating is 1-36 h, and further can be 2-24 h.

[0044] Preferably, the temperature of the precipitation reaction is 20-80℃.

[0045] More preferably, the temperature of the precipitation reaction is 25-60℃.

[0046] Preferably, the time of the precipitation reaction is 2-60 min.

[0047] More preferably, the time of the precipitation reaction is 5-45 min.

[0048] Preferably, in the hydrothermal reaction, the solid-liquid ratio of the precipitate and water is 1g:(10-100)mL.

[0049] More preferably, in the hydrothermal reaction, the solid-liquid ratio of the precipitate and water is 1g:(20-80)mL, further 1g:(25-75)mL.

[0050] Preferably, the time of the hydrothermal reaction is 0.25-24h.

[0051] More preferably, the time of the hydrothermal reaction is 0.5-12h, further 1-6h.

[0052] Preferably, after the hydrothermal reaction, cooling and filtration are further included.

[0053] Preferably, the temperature of the calcination is 250-900℃.

[0054] More preferably, the temperature of the calcination is 300-800℃, further 350-700℃.

[0055] Preferably, the time of the calcination is 1-36h.

[0056] More preferably, the time of the calcination is 2-24h, further 3-12h.

[0057] In a second aspect, the present application provides a cerium dioxide prepared by the above preparation method.

[0058] In a third aspect, the present application provides an application of cerium dioxide in polishing.

[0059] Preferably, the application is an application of cerium dioxide in preparing a polishing product.

[0060] More preferably, the polishing product is a polishing liquid.

[0061] Compared with the prior art, the present application has the following beneficial effects:

[0062] In the preparation method of the present application, by controlling the temperature of the hydrothermal reaction and using a sulfate salt, cerium dioxide with high Ce 4+ / Ce element content and small particle size dispersity can be prepared.

[0063] Specifically, by controlling the temperature of the hydrothermal reaction to convert water molecules into high-energy gaseous state, the impact of the gaseous water molecules changes the structure of the surface of the cerium precipitate, increases the specific surface area of the cerium precipitate, and makes the sulfate radical of the sulfate tightly adsorbed on the surface of the cerium precipitate. Not only can it prevent the subsequent generation of ceria particle agglomeration, but it is also conducive to reducing the particle size dispersion of ceria, but also can use its own negative charge to bind the oxygen in ceria, prevent its escape to form oxygen vacancies and increase the Ce 3+ content, thereby facilitating the improvement of the Ce 4+ / Ce element content of ceria.

[0064] In addition, the reason why the sulfate is selected instead of the carbonate in the present application is that in the system of the present application, the adsorption of sulfate on the surface of cerium precipitate is much stronger than that of carbonate, and the ability of sulfate to prevent ceria particle agglomeration and bind oxygen in ceria is stronger. BRIEF DESCRIPTION OF DRAWINGS

[0065] Figure 1 SEM image of ceria of Example 1.

[0066] Figure 2 SEM image of ceria of Example 6.

[0067] Figure 3 SEM image of ceria of Comparative Example 1.

[0068] Figure 4 SEM image of ceria of Comparative Example 2. DETAILED DESCRIPTION

[0069] In order to better illustrate the purpose, technical scheme and advantages of the present application, the present application will be further described below in conjunction with specific examples.

[0070] The experimental methods not specified in the following example implementation are usually carried out according to the conventional conditions in the field or according to the conditions recommended by the manufacturer; the raw materials, reagents, etc. used, if not specifically stated, are raw materials and reagents that can be obtained through commercial channels such as conventional markets.

[0071] Example 1

[0072] The present embodiment provides a ceria, and the preparation method thereof comprises the following steps:

[0073] S1. In 500 mL of 3 mol / L alkaline precipitant solution (sodium hydroxide aqueous solution), 300 L / h of oxidant air was introduced, then 500 mL of 0.6 mol / L trivalent cerium salt (cerium chloride CeCl3) aqueous solution was slowly added dropwise for mixing at 35℃, 600 rpm, the trivalent cerium salt aqueous solution was added dropwise for 2 h, then the reaction was carried out at 35℃ for 4 h to obtain 4-valent cerium hydroxide precipitate, which was filtered, and the precipitate was washed with deionized water until the washing liquid after washing was free of chloride ions, 65-68% mass fraction of concentrated nitric acid was added, and the mixture was stirred at 100℃ for 15 min to dissolve, thereby obtaining 4-valent cerium nitrate (1.5 mol / L);

[0074] S2. The 4-valent cerium nitrate (1.5 mol / L) prepared in step S1 was diluted with water to obtain a 0.12 mol / L aqueous solution of 4-valent cerium nitrate, and 1000 mL of the solution was heated at 80℃ for 3 h; then the temperature was adjusted to 60℃, and the pH of the system was adjusted to 8 with 0.025 mol / L sodium hydroxide aqueous solution for precipitation reaction for 15 min; the precipitate was separated by filtration, and deionized water was added to the precipitate at a solid-liquid ratio of 1 g precipitate:50 mL water and was dispersed again, 0.036 mol of sulfate (sodium sulfate) was added, and the mixture was placed in a reaction kettle for hydrothermal reaction at 150℃ for 2 h, and then was naturally cooled, filtered, and dried at 110℃ for 10 h, and then was calcined at 500℃ in air for 8 h, and then was cooled, thereby obtaining cerium dioxide;

[0075] In step S1, the ratio of the amount of substance of the alkaline precipitant (NaOH) to the amount of substance of the trivalent cerium salt (cerium chloride CeCl3) was 5:1;

[0076] In step S2, the ratio of the amount of substance of cerium in the aqueous solution of 4-valent cerium nitrate to the amount of substance of sulfate radical in the sulfate (sodium sulfate) was 1 mol:0.3 mol.

[0077] Examples 2-3 and Comparative Examples 1-2

[0078] Examples 2-3 and Comparative Examples 1-2 provide different cerium dioxides, which differ from Example 1 in that the temperature of the hydrothermal reaction in step S2 is different, and the rest are consistent with Example 1, as shown in the following table:

[0079] Table 1 Temperature of hydrothermal reaction in step S2 of Examples 1-3 and Comparative Examples 1-2

[0080] Temperature of hydrothermal reaction in step S2 / °C Example 1 150 Example 2 200 Example 3 120 Comparative Example 1 90 Comparative Example 2 250

[0081] Examples 4-6 and Comparative Example 3

[0082] Examples 4-6 and Comparative Example 3 provide different cerium dioxide, which differs from Example 1 in that the ratio of the amount of substance of cerium in the aqueous solution of cerium nitrate of valence 4 and the amount of substance of sulfate in the sulfate is different, and the rest is consistent with Example 1, as shown in the following table:

[0083] Table 2 Ratio of the amount of substance of cerium in the aqueous solution of cerium nitrate of valence 4 and the amount of substance of sulfate in the sulfate in Examples 1, 4-6 and Comparative Example 3

[0084]

[0085]

[0086] Examples 7-8 and Comparative Examples 4-5

[0087] Examples 7-8 and Comparative Examples 4-5 provide different cerium dioxide, which differs from Example 1 in that the kind of sulfate is different, and the rest is consistent with Example 1, as shown in the following table:

[0088] Table 3 Kind of sulfate in Examples 1, 7-8 and Comparative Examples 4-5

[0089] Kind of sodium sulfate Example 1 Sodium sulfate Example 7 Potassium sulfate Example 8 Ammonium sulfate Comparative Example 4 Sodium carbonate Comparative Example 5 Ammonium carbonate

[0090] Examples 9-10

[0091] Examples 9-10 provide different cerium dioxide, which differs from Example 1 in that the pH value of the adjusted system when adjusting the pH value of the system to carry out the precipitation reaction in step S2 is different, and the rest is consistent with Example 1, as shown in the following table:

[0092] Table 4 pH value of the system in step S2 in Examples 1, 9-10

[0093] pH of system in step S2 Example 1 pH = 8 Example 9 pH = 6 Example 10 pH = 10

[0094] Example 11

[0095] This example provides a cerium dioxide, which differs from Example 1 in that a commercially available cerium nitrate of valence 4 is used to prepare a 0.12 mol / L aqueous solution of cerium nitrate of valence 4 instead of using the cerium nitrate of valence 4 prepared in step S1 of Example 1 (1.5 mol / L) to dilute with water to prepare a 0.12 mol / L aqueous solution of cerium nitrate of valence 4, and the rest is consistent with Example 1.

[0096] Comparative Example 6

[0097] This comparative example provides a cerium dioxide, which differs from Example 1 in that after the precipitation reaction in step S2, no water and sulfate are added to carry out hydrothermal reaction, but direct calcination, as follows:

[0098] The preparation method of the cerium dioxide comprises the following steps:

[0099] S1. consistent with example 1;

[0100] S2. The tetravalent cerium nitrate (1.5 mol / L) prepared in step S1 is diluted with water to form a 0.12 mol / L tetravalent cerium nitrate aqueous solution, 1000 mL, heated at 80°C for 3h; then adjust the temperature to 60°C, and adjust the system pH = 8 with 0.025 mol / L sodium hydroxide aqueous solution for precipitation reaction for 15 min; filter separation and take the precipitate, calcine at 500°C for 8h under air atmosphere, and cool to obtain cerium dioxide;

[0101] In step S1, the ratio of the amount of substance of the basic precipitant (NaOH) to the amount of substance of the trivalent cerium salt (cerium chloride CeCl3) is 5:1.

[0102] Performance test

[0103] The cerium dioxide of each example and comparative example is tested as follows:

[0104] 1. Ce / Ce element content of cerium dioxide 4+ / Ce element content measurement:

[0105] (1) A series of different concentrations of tetravalent cerium nitrate (CAS No.: 13093-17-9) solution is prepared first, and then the absorbance of the tetravalent cerium nitrate solution at 320 nm is measured by spectrophotometry, and a standard curve is established;

[0106] (2) The cerium dioxide samples prepared in each example or comparative example are dissolved in 1 mol / L nitric acid solution to obtain sample solution A, and the absorbance of sample solution A is measured with 1 mol / L nitric acid solution as a reference, and the mass of tetravalent cerium (Ce 4+ ) in the cerium dioxide sample is calculated according to the standard curve, denoted as M4;

[0107] (3) The same mass of cerium dioxide samples prepared in each example or comparative example is taken as in step (2), dissolved in 1 mol / L nitric acid solution, and then the same mass of ammonium persulfate as the cerium dioxide is added to oxidize all the trivalent cerium (Ce 3+ ) in the cerium dioxide sample to tetravalent cerium (Ce 4+ ), to obtain sample solution B, and the absorbance of sample solution B is measured with 1 mol / L nitric acid solution containing ammonium persulfate as a reference, and the mass of cerium element (tetravalent cerium + trivalent cerium) in the cerium dioxide sample is calculated according to the standard curve, denoted as Mtotal;

[0108] (4) The Ce element content of each of the cerium dioxide samples of the examples or the comparative examples was calculated according to the following formula: 4+ The Ce element content (%):

[0109] Ce 4+ The Ce element content (%) = (M4 / Mtotal) x 100%;

[0110] 2. Particle size dispersity test of cerium dioxide:

[0111] The particle size distribution of each of the cerium dioxide samples of the examples or the comparative examples was tested by a Malvern Panalytical laser particle size analyzer Mastersizer 3000+Ultra, and the D10, D50, D90 values were recorded, and the particle size dispersity of the cerium dioxide was calculated according to the following formula:

[0112] The particle size dispersity of the cerium dioxide (%) = [(D90-D10) / D50] x 100%;

[0113] The smaller the value of the particle size dispersity of the cerium dioxide (%), the more uniform the particle size of the cerium dioxide;

[0114] The experimental results are shown in the following table:

[0115] Table 5 Test results of each of the examples and the comparative examples

[0116] Ce 4+ Ce element content (%)]]> Particle size dispersibility (%) Example 1 99.98 30.36 Example 2 99.5 33.52 Example 3 98.52 37.98 Example 4 99.43 34.59 Example 5 98.47 38.26 Example 6 97.79 44.81 Example 7 99.95 30.52 Example 8 97.1 49.29 Example 9 99.88 33.71 Example 10 99.85 38.01 Example 11 99.93 30.26 Comparative Example 1 94.37 74.99 Comparative Example 2 95.5 62.51 Comparative Example 3 94.21 73.51 Comparative Example 4 95.45 63.95 Comparative Example 5 95.11 65.07 Comparative Example 6 93.15 81.78

[0117] Figure 1 SEM image of cerium dioxide of Example 1. Figure 2 SEM image of cerium dioxide of Example 6. Figure 3 SEM image of cerium dioxide of Comparative Example 1. Figure 4 SEM image of cerium dioxide of Comparative Example 2.

[0118] From Figures 1-4 As can be seen from Table 6, in the preparation method of the present application, cerium dioxide with high Ce 4+ element content and small particle size dispersity can be prepared by controlling the temperature of the hydrothermal reaction and using a sulfate.

[0119] As can be seen from Examples 1, 7-8 and Comparative Examples 4-5, in the system of the present application, the adsorption of sulfate on the surface of cerium precipitate is much stronger than that of carbonate, and the sulfate has stronger ability to prevent cerium dioxide particles from agglomerating and to bind oxygen in cerium dioxide, so when a sulfate is selected, the cerium dioxide has lower particle size dispersity and higher Ce 4+ element content. In addition, the presence of ammonium affects the acid-base property of the system, resulting in a decrease in the adsorption of sulfate on the surface of cerium precipitate.

[0120] Finally, it should be noted that the above examples are merely intended to illustrate the technical solutions of the present application and not to limit the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A method for preparing cerium dioxide, characterized in that, The preparation method includes the following steps: Aqueous solutions of tetravalent cerium nitrate are heated to adjust the pH of the system and induce a precipitation reaction. The precipitate is separated, and water and sulfate are added to induce a hydrothermal reaction. The precipitate is then calcined to obtain cerium dioxide. The temperature of the hydrothermal reaction is 110-200℃.

2. The method for preparing cerium dioxide as described in claim 1, characterized in that, Includes at least one of the following (1)-(2): (1) The temperature of the hydrothermal reaction is 120-200℃; (2) The ratio of the amount of cerium in the aqueous solution of tetravalent cerium nitrate to the amount of sulfate in the sulfate is 1 mol: (0.1-0.8) mol.

3. The method for preparing cerium dioxide as described in claim 2, characterized in that, Includes at least one of the following (1)-(2): (1) The temperature of the hydrothermal reaction is 150-200℃; (2) The ratio of the amount of cerium in the aqueous solution of tetravalent cerium nitrate to the amount of sulfate in the sulfate is 1 mol: (0.3-0.5) mol.

4. The method for preparing cerium dioxide as described in claim 1, characterized in that, Includes at least one of the following (1)-(2): (1) The sulfate is at least one of sodium sulfate, potassium sulfate, ammonium sulfate, and ammonium bisulfate; (2) The pH of the system is 6-10.

5. The method for preparing cerium dioxide as described in claim 4, characterized in that, The system has a pH of 6-8.

6. The method for preparing cerium dioxide as described in claim 1, characterized in that, The pH adjuster of the system is at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, and sodium bicarbonate.

7. The method for preparing cerium dioxide as described in claim 1, characterized in that, Includes at least one of the following (1)-(3): (1) The heating temperature is 60-95℃; (2) The precipitation reaction is carried out at a temperature of 20-80℃; (3) The calcination temperature is 250-900℃.

8. The method for preparing cerium dioxide as described in claim 1, characterized in that, The method for preparing tetravalent cerium nitrate includes: reacting a trivalent cerium salt aqueous solution and an alkaline precipitant solution under oxidant conditions to obtain tetravalent cerium hydroxide precipitate, and then dissolving it in nitric acid to obtain tetravalent cerium nitrate.

9. A cerium dioxide prepared by the preparation method according to any one of claims 1-8.

10. An application of cerium dioxide in polishing as described in claim 9.

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