Abstract: Provided are a sintered ceramic and a ceramic sphere which are inhibited from suffering surface peeling due to fatigue resulting from repetitions of loading and can attain an improvement in dimensional accuracy when subjected to surface processing and which have excellent wear resistance and durability.

Abstract: Provided are a sintered ceramic and a ceramic sphere which are inhibited from suffering surface peeling due to fatigue resulting from repetitions of loading and can attain an improvement in dimensional accuracy when subjected to surface processing and which have excellent wear resistance and durability. A ceramic-sphere inspection device is also provided with which a ceramic sphere is inspected for a flaw present in the surface layer and for snow flakes without destroying the ceramic sphere. The device is a ceramic-sphere inspection device (100) in which a ceramic sphere (S) is rotatably supported in a given position and illuminating light emitted from a light projector (110) is detected with a light receiver (120) to evaluate the state of the inner part of the surface layer, and has been configured so that the light receiver (120) does not detect the light emitted from the light projector (110) and reflected at the surface of the ceramic sphere.

Abstract: Provided are a sintered ceramic and a ceramic sphere which are inhibited from suffering surface peeling due to fatigue resulting from repetitions of loading and can attain an improvement in dimensional accuracy when subjected to surface processing and which have excellent wear resistance and durability. A ceramic-sphere inspection device is also provided with which a ceramic sphere is inspected for a flaw present in the surface layer and for snow flakes without destroying the ceramic sphere. The device is a ceramic-sphere inspection device (100) in which a ceramic sphere (S) is rotatably supported in a given position and illuminating light emitted from a light projector (110) is detected with a light receiver (120) to evaluate the state of the inner part of the surface layer, and has been configured so that the light receiver (120) does not detect the light emitted from the light projector (110) and reflected at the surface of the ceramic sphere.

Abstract: Provided are a sintered ceramic and a ceramic sphere which are inhibited from suffering surface peeling due to fatigue resulting from repetitions of loading and can attain an improvement in dimensional accuracy when subjected to surface processing and which have excellent wear resistance and durability. A ceramic-sphere inspection device is also provided with which a ceramic sphere is inspected for a flaw present in the surface layer and for snow flakes without destroying the ceramic sphere. The device is a ceramic-sphere inspection device (100) in which a ceramic sphere (S) is rotatably supported in a given position and illuminating light emitted from a light projector (110) is detected with a light receiver (120) to evaluate the state of the inner part of the surface layer, and has been configured so that the light receiver (120) does not detect the light emitted from the light projector (110) and reflected at the surface of the ceramic sphere.

Abstract: The present invention relates to a zirconia based sintered body excellent in durability, characterized in that in Y2O3-toughened zirconia based sintered body, (a) ZrO2 contained therein is mainly composed of tetragonal ZrO2, and the sintered body contains Y2O3 as a secondary component and further SiO2 and Al2O3 as a third component; (b) the sintered body has a molar ratio of Y2O3/ZrO2 in the range of 1.5/98.5 to 4/96; (c) the sintered body has a SiO2 content of 0.05 to 2.5 wt %; (d) the sintered body has a Al2O3 content of 0.05 to 3.0 wt %; (e) the sintered body has an average crystal grain diameter of 0.7 ?m or less; (f) SiO2 (wt %)×average crystal grain diameter (?m) takes a value ranging from 0.03 to 0.5; (g) the sintered body contains at least one oxide of Na2O, K2O, CaO and Fe2O3 as an impurity and a weight ratio of SiO2/(total amount of the impurity) is 5 or more; and (h) the sintered body has a bulk density of 5.