| 摘要 |
<p>An translucent polycrystalline ceramic is disclosed which is capable of transmitting visible light and which is excellent in strength, hardness, abrasion resistance, light transmittance, transparency and high-temperature characteristics and usable as a material, for instance, for cutting tools, outer tubes for high pressure sodium lamps and high temperature furnace window plates. The translucent polycrystalline ceramic has at least one of the following characteristic features: (1) a mean particle size of crystal particles formed inside the ceramic is not larger than 1.0 mu m, (2) a mean aspect ratio thereof is from 1.0 to 1.5. (3) a density thereof is substantially a theoretical density, (4) a light transmittance through its thickness of 1 mm is at least 50%, (5) a mean facet length of crystal particles formed inside the ceramic is not longer than a maximum wave length of the light. One of the embodiments is a translucent polycrystalline Al2O3 ceramic containing 0.02 - 2.0 mol% of oxide of metal belonging to group IIIA and/or IVA (excluding Ti), having its density of at least 3.98 g/cm<3>, a mean crystal particle size of 0.3 - 1.0 mu m, its bending strength of at least 1900 MPa and its Vickers hardness of at least 850 at 1000 DEG C.</p> |
