Cerium oxide and preparation method and application thereof

Abstract

The invention discloses cerium oxide as well as a preparation method and application thereof. The preparation method of cerium oxide comprises the following steps: (1) putting water-insoluble cerium salt into water to obtain water-insoluble cerium salt slurry; then, a dispersing agent is added into the non-water-soluble cerium salt slurry, and a non-water-soluble cerium salt suspension is obtained; 2) performing ball milling on the non-water-soluble cerium salt suspension to obtain ball-milled pretreatment slurry; then, the ball-milling pretreatment slurry is subjected to sanding, and sanding slurry is obtained; 3) filtering the sanded slurry, and washing and drying filter residues to obtain a precursor; and 4) roasting the precursor at the temperature of 800-1200 DEG C to prepare the cerium oxide. The cerium oxide prepared by the method disclosed by the invention is in a submicron level, uniform in morphology, good in dispersity and excellent in polishing performance.

Description

Technical Field

[0001] The present invention relates to cerium oxide, a preparation method thereof, and uses thereof. Background Art

[0002] Cerium-based rare earth polishing powders enjoy the reputation of "king of polishing" and dominate the polishing process of glass substrates, especially in the fields of cover glass and optical glass polishing. However, with the development of science and technology, the requirements for polishing materials in high-tech fields are getting higher and higher. Currently, the particle sizes of rare earth polishing powders are generally in the micron range, with a wide particle size distribution and serious agglomeration. During the polishing process of semiconductor substrates and high-end display glass substrates, it is easy to cause problems such as scratches on the surface of the polished wafers and relatively high roughness, and cannot meet the surface requirements of the polished wafers. Therefore, there is an urgent need to develop a cerium oxide polishing abrasive with controllable particle size and good dispersibility. Summary of the Invention

[0003] In view of this, one object of the present invention is to provide a preparation method of cerium oxide. The cerium oxide prepared by this method has a particle size of 100 - 500 nm and can significantly improve the surface quality of polished parts as a polishing abrasive. Another object of the present invention is to provide the cerium oxide prepared by the above preparation method. Still another object of the present invention is to provide the uses of the above cerium oxide.

[0004] The present invention adopts the following technical solutions to achieve the above objects.

[0005] On the one hand, the present invention provides a preparation method of cerium oxide, comprising the following steps:

[0006] 1) Placing a water-insoluble cerium salt in water to obtain a water-insoluble cerium salt slurry; then, adding a dispersant to the water-insoluble cerium salt slurry to obtain a water-insoluble cerium salt suspension;

[0007] 2) Ball-milling the water-insoluble cerium salt suspension obtained in step 1) to obtain a ball-milled pretreatment slurry; wherein, the rotation speed of the ball-milling is 200 - 800 rpm; then, sand-milling the ball-milled pretreatment slurry to obtain a sand-milled slurry; wherein, the rotation speed of the sand-milling is 3000 - 4000 rpm;

[0008] 3) Filtering the sand-milled slurry obtained in step 2), washing and drying the filter residue to obtain a precursor;

[0009] 4) Calcining the precursor obtained in step 3) at 800 - 1200 °C to obtain cerium oxide.

[0010] According to the preparation method of the present invention, preferably, in step 1), the mass ratio of the water-insoluble cerium salt to water can be 0.05 - 0.25:1, preferably 0.1 - 0.2:1.

[0011] In the present invention, the water used can be ultrapure water, deionized water or distilled water, preferably ultrapure water or deionized water.

[0012] According to the preparation method of the present invention, preferably, in step 1), the mass ratio of the dispersant to the water-insoluble cerium salt slurry can be 0.001 - 0.01:1, preferably 0.001 - 0.005:1.

[0013] Limiting the ratio of the water-insoluble cerium salt to water and the ratio of the dispersant to the water-insoluble cerium salt slurry within the above ranges is beneficial to better disperse the water-insoluble cerium salt in water, and the obtained water-insoluble cerium salt suspension is more conducive to making cerium oxide particles with uniform particle size and good dispersibility.

[0014] According to the preparation method of the present invention, preferably, in step 1), the water-insoluble cerium salt can be at least one of cerium carbonate and cerium oxalate, preferably cerium carbonate or cerium oxalate.

[0015] According to the preparation method of the present invention, preferably, in step 1), the dispersant can be selected from at least one of sodium hexametaphosphate, sodium citrate, magnesium aluminum silicate, polyvinylpyrrolidone, polyethylene glycol, cetyltrimethylammonium bromide, and sodium dodecylbenzenesulfonate, preferably at least one of sodium hexametaphosphate, sodium citrate, polyvinylpyrrolidone, polyethylene glycol, and cetyltrimethylammonium bromide.

[0016] According to the preparation method of the present invention, preferably, in step 1), after adding the dispersant, a stirring step can further be included. The speed of the stirring is 600 - 1000 rpm, and the time of the stirring is 10 - 30 min.

[0017] In the present invention, the stirring can be any type of stirring method well known in the art, and no special limitation is made here. For example, but not limited to, it can be magnetic stirring or mechanical stirring.

[0018] A reasonable stirring speed and stirring time can ensure that the water-insoluble cerium salt is more evenly dispersed in water.

[0019] In the present invention, the rotation speed of the ball milling can be 200 - 800 rpm, preferably 250 - 500 rpm. The time of the ball milling can be 2 - 5 h, preferably 3 - 4 h.

[0020] In the present invention, ball milling can be achieved using any type of ball mill known in the art, and no special limitation is imposed here. The grinding media for ball milling can be grinding media made of any material known in the art. According to one embodiment of the present invention, the grinding media for ball milling is preferably zirconium beads, and the particle size of the zirconium beads can be 1 - 30 mm, preferably 5 - 20 mm. In the present invention, grinding media with the same particle size can be used, or multiple specifications of grinding media with different particle sizes can be used. According to a preferred embodiment of the present invention, three specifications of zirconium beads with particle sizes of 20 mm, 15 mm, and 5 mm respectively can be mixed as the grinding media. The dosages of the three specifications of zirconium beads can be 20 - 80 g, 20 - 80 g, and 50 - 100 g respectively, preferably 40 - 70 g, 40 - 70 g, and 60 - 90 g respectively. The mass ratio of the water-insoluble cerium salt to the grinding media can be 1:0.05 - 1, preferably 1:0.1 - 0.5.

[0021] Limiting the conditions of ball milling within the above range is beneficial for the preliminary control of the particle size of the water-insoluble cerium salt with a particle size of more than 100 μm, reducing the particle size of the water-insoluble cerium salt, thereby shortening the time of sand milling and improving the efficiency of sand milling. At the same time, it is beneficial to prevent the clogging of the screen of the sand mill.

[0022] In the present invention, sand milling can be achieved using any type of sand mill known in the art, and no special limitation is imposed here. The grinding media for sand milling can be grinding media made of any material known in the art. According to one embodiment of the present invention, the grinding media for sand milling is preferably zirconium beads, and the particle size of the zirconium beads can be 0.1 - 0.5 mm, preferably 0.2 - 0.3 mm.

[0023] According to the preparation method of the present invention, preferably, in step 2), the rate of cyclic slurry supply for the sand milling can be 100 - 200 mL / min, preferably 120 - 180 mL / min.

[0024] According to one embodiment of the present invention, the aperture of the screen used for sand milling can be 0.05 - 0.3 mm, preferably 0.1 - 0.2 mm.

[0025] In the present invention, the rotation speed of the sand milling can be 3000 - 4000 rpm, preferably 3500 - 3800 rpm. The time of the sand milling can be 5 - 30 min, preferably 10 - 20 min.

[0026] Limiting the conditions of sand milling within the above range can effectively control the particle size and dispersibility of the water-insoluble cerium salt, which is beneficial for obtaining cerium oxide with good dispersibility and concentrated particle size by high-temperature roasting.

[0027] In step 3) of the present invention, filtration can be carried out by any filtration method known in the art, and no special limitation is made here. For example, it can be gravity filtration, pressure filtration, centrifugal filtration, vacuum filtration, etc. All kinds of filtration methods can be realized by equipment known in the art. According to an embodiment of the present invention, centrifugal filtration or suction filtration is preferably used. According to an embodiment of the present invention, the filtration can be centrifugal filtration. The rotation speed of centrifugal filtration can be 5000 - 10000 rpm, preferably 6500 - 8500 rpm. The time of centrifugal filtration can be 5 - 20 min, preferably 8 - 15 min.

[0028] In step 3) of the present invention, the detergent can be at least one of water and C1 - C3 alkyl alcohols; preferably at least one of water and C1 - C3 normal alkyl alcohols; more preferably at least one of deionized water or ultrapure water, methanol, and ethanol.

[0029] In the present invention, C1 - C3 alkyl alcohols can include but are not limited to methanol, ethanol, n - propanol, isopropanol, etc.

[0030] The number of washing times in the present invention can be 1 - 5 times; preferably 1 - 3 times. The washing method can be washing with one detergent or using different detergents in different washing times, and no special limitation is made here. According to an embodiment of the present invention, ethanol can be used to wash 1 - 2 times first, and then filtration is carried out again to obtain the filter residue.

[0031] In step 3) of the present invention, drying can be realized by any type of drying method known in the art, and no special limitation is made here. For example but not limited to, it can be heat drying or freeze drying. According to an embodiment of the present invention, it can be heat drying, and the drying temperature can be 50 - 120 °C, preferably 60 - 100 °C. The drying time can be 6 - 20 h, preferably 8 - 15 h.

[0032] According to the preparation method of the present invention, preferably, in step 4), the calcination temperature of the precursor can be 800 - 1200 °C, preferably 900 - 1150 °C. The calcination time can be 2 - 6 h, preferably 3 - 5 h.

[0033] Reasonable calcination conditions can ensure that the prepared cerium oxide has uniform particle size, good dispersibility, and the particle size is sub - micron level, which is beneficial to improving the polishing quality of cerium oxide as a polishing abrasive.

[0034] In the present invention, calcination can be realized by any type of calcination equipment known in the art, and no special limitation is made here. For example but not limited to, it can be a muffle furnace, a vacuum calcination furnace, a rotary kiln, a tunnel kiln, etc., preferably a muffle furnace or a vacuum calcination furnace.

[0035] In the present invention, after the roasting in step 4) is completed, it may further include the steps of cooling and grinding the roasted product.

[0036] The cooling can be achieved by any type of cooling method known in the art, and no special limitation is made herein. For example, but not limited to, it can be natural cooling or air cooling.

[0037] The grinding can be achieved by any type of grinding method known in the art, and no special limitation is made herein. For example, but not limited to, it can be grinding with a mortar or grinding with a grinder.

[0038] On the other hand, the present invention also provides cerium oxide prepared by the above preparation method. The cerium oxide has a uniform morphology and good dispersibility. The cerium oxide of the present invention is sub-micron sized, and its particle size can be 100 - 500 nm, preferably 200 - 400 nm.

[0039] On yet another aspect, the present invention also provides the use of the above cerium oxide as a polishing abrasive. Using the cerium oxide of the present invention as a polishing abrasive to polish a polished part, the average roughness of the polished part after polishing can be at most 0.38 nm, preferably at most 0.36 nm. The root mean square roughness of the polished part after polishing can be at most 0.6 nm, preferably at most 0.55 nm.

[0040] The preparation method of the present invention is simple in operation and stable in process. The cerium oxide prepared by the present invention is sub-micron sized, has a uniform morphology, good dispersibility, and excellent polishing performance. Description of the Drawings

[0041] Figure 1 SEM image of cerium carbonate in Example 1.

[0042] Figure 2 SEM image of the cerium carbonate in Example 1 after sanding treatment.

[0043] Figure 3 XRD pattern of the cerium oxide prepared in Example 1.

[0044] Figure 4 SEM image of the cerium oxide prepared in Example 1.

[0045] Figure 5 SEM image of the cerium oxide prepared in Example 2.

[0046] Figure 6 AFM image of the surface of a 2-inch silicon wafer before polishing with the cerium oxide prepared in Experimental Example 1.

[0047] Figure 7 AFM image of the surface of a 2-inch silicon wafer after polishing with the cerium oxide prepared in Example 1.

[0048] Figure 8 AFM image of the surface of a 2-inch silicon wafer polished with cerium oxide prepared in Example 2.

[0049] Figure 9 SEM image of cerium oxide prepared in Comparative Example 1.

[0050] Figure 10 AFM image of the surface of a 2-inch silicon wafer polished with cerium oxide prepared in Comparative Example 1. Detailed implementation manners

[0051] The present invention will be further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0052] The "average roughness" referred to in the present invention is the average distance between the actual surface height of the polished part and the average profile line, usually denoted as Ra, with the unit of nanometer (nm).

[0053] The "root mean square roughness" referred to in the present invention is the square root of the sum of the squares of the average profile line deviations on the surface of the polished part, usually denoted as Rq, with the unit of nanometer (nm).

[0054] <Testing method>

[0055] XRD measurement: Test was carried out using an X'Pert PRO X-ray diffractometer. The sample was crushed into fine particles using a mortar. Using the X'Pert PRO X-ray diffractometer, with Cu target and Kα ray, The scanning speed was 2° per second, and the test angle range was 5 - 80° for analyzing the crystal structure of the sample.

[0056] SEM measurement: Test was carried out using a ZEISS Sigma 500 field emission scanning electron microscope. The sample was placed in an anhydrous ethanol solution, ultrasonically dispersed for 5 min, then dropped onto a silicon wafer, dried and sputter-coated with gold. The ZEISS Sigma 500 field emission scanning electron microscope was used to observe the microscopic morphology of the sample.

[0057] AFM measurement: Test was carried out using a Bruker Dimension Icon atomic force microscope. The test piece was ultrasonically cleaned, dried, and then placed on the atomic force microscope test stage. The test mode was the tapping mode, and the probe model was Bruker RFESPA - 75.

[0058] Polishing: Polishing was carried out using a Struers Tegramin - 25 polishing machine. The polishing pad was Struers MD - CHEM. The rotation speed of the wafer head was 80 rpm, the rotation speed of the polishing disc was 90 rpm, the polishing flow rate was 50 mL / min, the polishing pressure was 60 N, and the polishing time was 10 min.

[0059] <Raw material description>

[0060] Unless otherwise specified, the raw materials used in the following examples are all commercially available products.

[0061] Among them, cerium carbonate was purchased from Shanghai Macklin Biochemical Co., Ltd., with a specification of 99.9% (purity).

[0062] The 2-inch silicon wafer was purchased from Henan Micron Optoelectronics Technology Co., Ltd., with a diameter of 50.8 mm, a Mohs hardness of 7, and a density of 2.33 g / cm 3 .

[0063] Example 1

[0064] Preparation of cerium oxide:

[0065] (1) Place 40 g of cerium carbonate in 360 mL of deionized water to obtain a cerium carbonate slurry; then, add 0.4 g of sodium hexametaphosphate to the cerium carbonate slurry, and then stir at a speed of 800 rpm for 30 min to obtain a cerium carbonate suspension.

[0066] (2) Use zirconium beads with three specifications of particle sizes of 20 mm, 15 mm, and 5 mm as grinding media. The masses of the three specifications of zirconium beads added are 60 g, 60 g, and 80 g respectively. According to the mass ratio of the cerium carbonate slurry to the grinding media of 400:200, ball-mill the cerium carbonate suspension at a rotational speed of 300 rpm for 4 h to obtain a ball-milled pretreatment slurry; then, use a sieve with a pore size of 0.1 mm, use zirconium beads with a particle size of 0.2 mm as the grinding media, and sand-mill the ball-milled pretreatment slurry at a rotational speed of 3700 rpm for 10 min according to a circulating slurry supply rate of 140 mL / min to obtain a sand-milled slurry.

[0067] (3) Centrifuge the sand-milled slurry at 8000 rpm for 10 min, filter it, wash the filter residue once with ethanol and then filter it again. Then, dry the filter residue at 80 °C for 10 h to obtain a precursor.

[0068] (4) Place the precursor in a muffle furnace, calcine it at 1000 °C for 4 h, and grind it after natural cooling to obtain cerium oxide.

[0069] Example 2

[0070] Preparation of cerium oxide:

[0071] (1) Place 60 g of cerium carbonate in 340 mL of deionized water to obtain a cerium carbonate slurry; then, add 0.6 g of sodium hexametaphosphate to the cerium carbonate slurry, and then stir at a speed of 800 rpm for 30 min to obtain a cerium carbonate suspension.

[0072] (2) Zircon beads with three specifications of particle sizes of 20 mm, 15 mm and 5 mm are used as grinding media. The added masses of the zircon beads of the three specifications are 60 g, 60 g and 80 g respectively. According to the mass ratio of cerium carbonate slurry to grinding media of 400:200, the cerium carbonate suspension is ball-milled at 300 rpm for 4 h to obtain a ball-milled pre-treatment slurry; then, using a sieve with a pore size of 0.1 mm and zircon beads with a particle size of 0.2 mm as the grinding media, according to the circulating slurry supply rate of 140 mL / min, the ball-milled pre-treatment slurry is sand-milled at 3700 rpm for 15 min to obtain a sand-milled slurry.

[0073] (3) The sand-milled slurry is filtered and centrifuged at 8000 rpm for 10 min. The filter residue is washed once with ethanol and then filtered again. Then the filter residue is dried at 80 °C for 10 h to obtain a precursor.

[0074] (4) The precursor is placed in a muffle furnace and calcined at 1100 °C for 4 h. After natural cooling, it is ground to obtain cerium oxide.

[0075] Comparative Example 1

[0076] Preparation of cerium oxide (only ball-milled, not sand-milled):

[0077] (1) 40 g of cerium carbonate is placed in 360 mL of deionized water to obtain a cerium carbonate slurry; then, 0.4 g of sodium hexametaphosphate is added to the cerium carbonate slurry, and then it is stirred at a speed of 800 rpm for 30 min to obtain a cerium carbonate suspension.

[0078] (2) Zircon beads with three specifications of particle sizes of 20 mm, 15 mm and 5 mm are used as grinding media. The added masses of the zircon beads of the three specifications are 60 g, 60 g and 80 g respectively. And according to the mass ratio of cerium carbonate slurry to grinding media of 400:200, the cerium carbonate suspension is ball-milled at 300 rpm for 4 h to obtain a ball-milled pre-treatment slurry.

[0079] (3) The ball-milled slurry is centrifuged at 8000 rpm for 10 min, filtered. The filter residue is washed once with ethanol and then filtered again. Then the filter residue is dried at 80 °C for 10 h to obtain a precursor. (4) The precursor is placed in a muffle furnace and calcined at 1000 °C for 4 h. After natural cooling, it is ground to obtain cerium oxide.

[0080] Experimental Example 1

[0081] The cerium carbonate raw material of Example 1 is detected by SEM (scanning electron microscope), and the results are as Figure 1 shown. The cerium carbonate after sand-milling in Example 1 is detected by SEM, and the results are as Figure 2 shown.

[0082] It can be seen from Figure 1 and Figure 2 that the cerium carbonate raw material is an aggregate with a size of more than 100 μm. After sanding, the lamellar structure of cerium carbonate is opened, and the size is reduced to the sub-micron level.

[0083] The cerium oxide obtained in Example 1 was respectively subjected to XRD (X-ray diffraction) and SEM tests, and the results are as Figure 3 and Figure 4 shown. The cerium oxide obtained in Example 2 was subjected to SEM test, and the result is as Figure 5 shown.

[0084] It can be seen from Figure 3 that the diffraction peaks of the XRD pattern are sharp, and the peak positions correspond to the CeO2 diffraction peaks identified by the standard PDF card JCPDS No.89-8436, indicating that the material obtained in Example 1 is of the cerium oxide crystal form and has good crystallinity. It can be seen from Figure 4 that the particle morphology of the cerium oxide obtained in Example 1 is uniform, with good dispersion, and the particle size is in the range of 200-400 nm, belonging to sub-micron cerium oxide. It can be seen from Figure 5 that the particle morphology of the cerium oxide obtained in Example 2 is uniform, with good dispersion, and the particle size is in the range of 200-400 nm, belonging to sub-micron cerium oxide.

[0085] The cerium oxides obtained in Examples 1 and 2 were respectively used as polishing abrasives to polish a 2-inch silicon wafer, and the surfaces of the 2-inch silicon wafer before and after polishing were respectively subjected to AFM (atomic force microscope) tests. The AFM test results of the surface of the 2-inch silicon wafer before and after polishing with the cerium oxide obtained in Example 1 are respectively as Figure 6 and Figure 7 shown. The AFM test results of the surface of the 2-inch silicon wafer before and after polishing with the cerium oxide obtained in Example 2 are respectively as Figure 6 and Figure 8 shown.

[0086] It can be seen from Figure 6 and Figure 7 that on the surface of the 2-inch silicon wafer before polishing with the cerium oxide obtained in Example 1, the average roughness (Ra) and root mean square roughness (Rq) within a range of 5 μm×5 μm are 0.904 nm and 1.17 nm respectively. After polishing, the average roughness (Ra) and root mean square roughness (Rq) are respectively reduced to 0.331 nm and 0.416 nm, and the surface quality after polishing is significantly improved.

[0087] It can be seen from Figure 6 and Figure 8It can be seen that the average roughness (Ra) and root mean square roughness (Rq) of the 2-inch silicon wafer surface before cerium oxide polishing prepared in Example 2 within the range of 5 μm×5 μm are 0.904 nm and 1.17 nm respectively. The average roughness (Ra) and root mean square roughness (Rq) after polishing are reduced to 0.353 nm and 0.507 nm respectively, and the surface quality after polishing is significantly improved.

[0088] Comparative Experiment Example 1

[0089] The cerium oxide obtained in Comparative Example 1 was subjected to SEM examination, and the results were as follows: Figure 9 The AFM test results of the 2-inch silicon wafer surface before and after polishing using the cerium oxide prepared in Comparative Example 1 are shown as follows: Figure 6 and Figure 10 shown.

[0090] Depend on Figure 9 It can be seen that the cerium oxide particles prepared in Comparative Example 1 are adhered to each other, severely agglomerated, and have poor dispersibility.

[0091] Depend on Figure 6 and Figure 10 It can be seen that the average roughness (Ra) and root mean square roughness (Rq) of the 2-inch silicon wafer surface before cerium oxide polishing prepared in Comparative Example 1 within the range of 5μm×5μm are 0.904nm and 1.17nm respectively. The average roughness (Ra) and root mean square roughness (Rq) after polishing are 0.568nm and 0.955nm respectively. The surface roughness of the 2-inch silicon wafer after polishing is significantly greater than the result of the experimental example.

[0092] The present invention is not limited to the above-mentioned embodiments. Without departing from the essential content of the present invention, any deformation, improvement and substitution that can be conceived by those skilled in the art shall fall within the scope of the present invention.

Claims

1. A method for preparing cerium oxide, comprising the following steps: 1) Place an insoluble cerium salt in water to obtain an insoluble cerium salt slurry; then, add a dispersant to the insoluble cerium salt slurry to obtain an insoluble cerium salt suspension; 2) Ball-mill the insoluble cerium salt suspension obtained in step 1) to obtain a ball-milled pretreatment slurry; wherein, the rotation speed of the ball-milling is 200 - 800 rpm; then, sand-mill the ball-milled pretreatment slurry to obtain a sand-milled slurry; wherein, the rotation speed of the sand-milling is 3000 - 4000 rpm; 3) Filter the sand-milled slurry obtained in step 2), wash and dry the filter residue to obtain a precursor; 4) Calcinate the precursor obtained in step 3) at 800 - 1200 °C to obtain cerium oxide.

2. The preparation method according to claim 1, characterized in that, In step 1), the mass ratio of the insoluble cerium salt to water is 0.05 - 0.25:

1.

3. The preparation method according to claim 1, characterized in that, In step 1), the mass ratio of the dispersant to the insoluble cerium salt slurry is 0.001 - 0.01:

1.

4. According to the preparation method described in claim 1, wherein: In step 1), the insoluble cerium salt is at least one of cerium carbonate and cerium oxalate; In step 1), the dispersant is selected from at least one of sodium hexametaphosphate, sodium citrate, magnesium aluminum silicate, polyvinylpyrrolidone, polyethylene glycol, cetyltrimethylammonium bromide, and sodium dodecylbenzenesulfonate.

5. The preparation method according to claim 1, characterized in that In step 1), after adding the dispersant, a stirring step is further included, the speed of the stirring is 600 - 1000 rpm, and the time of the stirring is 10 - 30 min.

6. The preparation method according to claim 1, wherein In step 2), the time of the ball-milling is 2 - 5 h; the time of the sand-milling is 5 - 30 min.

7. The preparation method according to claim 1, characterized in that, In step 2), the rate of the circulating slurry supply for the sand-milling is 100 - 200 mL / min.

8. The preparation method according to claim 1, wherein In step 4), the time of the calcination is 2 - 6 h.

9. A cerium oxide prepared by the preparation method according to any one of claims 1 to 8, characterized in that, The particle size of the cerium oxide is 100 - 500 nm.

10. Use of the cerium oxide according to claim 9 as a polishing abrasive.

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