Abstract: To provide a technique with which in a case where sulfonic acid-modified aqueous anionic sol is used as abrasive grain, in a polishing composition for polishing an object to be polished that contains SiN, the stability of the SiN polishing rate with time can be improved, and the content of hydrogen peroxide can be decreased.

Abstract: A polishing composition of the present invention contains abrasive grains each having a surface with protrusions. Parts of the abrasive grains have larger particle diameters than the volume-based average particle diameter of the abrasive grains, and the average of values respectively obtained by dividing a height of each protrusion on the surface of each abrasive grain belonging to the parts of the abrasive grains by the width of a base portion of the same protrusion is 0.170 or more. Protrusions on the surfaces of abrasive grains belonging to the parts of the abrasive grains that have larger particle diameters than the volume-based average particle diameter of the abrasive grains have an average height of 3.5 nm or more. The polishing composition has a content of an organic alkali of 100 mmol or less per kilogram of the abrasive grains in the polishing composition.

Abstract: A polishing composition of the present invention contains abrasive grains each having a surface with protrusions. Parts of the abrasive grains have larger particle diameters than the volume-based average particle diameter of the abrasive grains, and the average of values respectively obtained by dividing a height of each protrusion on the surface of each abrasive grain belonging to the parts of the abrasive grains by the width of a base portion of the same protrusion is 0.170 or more. Protrusions on the surfaces of abrasive grains belonging to the parts of the abrasive grains that have larger particle diameters than the volume-based average particle diameter of the abrasive grains have an average height of 3.5 nm or more. The polishing composition has a content of an organic alkali of 100 mmol or less per kilogram of the abrasive grains in the polishing composition.

Abstract: An efficient polishing method for polishing an alloy material to have an excellent mirror surface is provided. The alloy material contains a main component and 0.1% by mass or more of an element that has a Vickers hardness (HV) different from the Vickers hardness of the main component by 5 or more. A polishing composition used in the polishing method contains abrasive grains and an oxidant. The alloy material is preferably an aluminum alloy, a titanium alloy, a stainless steel, a nickel alloy, or a copper alloy. It is also preferable that the alloy material is subjected to preliminary polishing before being subjected to polishing in which the polishing composition is used.