Patent ID: 8158544
Filing Date: 2012-04-17
Classification: C04B,Y10T

Abstract:
1. An yttria sintered body having a bending strength of 180 MPa or more and a dielectric loss tan δ of 1×10 −4 or less in the frequency range from 1 to 20 GHz, wherein the yttria sintered body contains yttria of 99.9% by mass or more, has a porosity of 1% or less and an average crystal grain size of 3 μm or less, has a surface roughness (Ra) of 0.05 to 5 μm, and the cumulative frequency ratio calculated from the following formula is 3 or less: where, the individual symbols D90 and D50 are calculated as follows: D90: the crystal grain size (μm) at which the cumulative number of grains as calculated from the smaller grain size side is 90% in a grain size distribution below; and D50: the crystal grain size (μm) at which the cumulative number of grains as calculated from the smaller grain size side is 50% in the grain size distribution below, where the grain size distribution is obtained by the following steps: (1) taking a photograph of crystal grain microstructure of the yttria sintered body; (2) measuring a major axis and a minor axis on the crystal grains; (3) calculating an average grain size by averaging out the major axis and the minor axis; and (4) counting the number of each average grain size.