Translucent zirconia sintered body, process for producing the same, and use of the same

Abstract

A subject of the invention relates to providing a powder for a translucent zirconia sintered body which is necessary for the production of a zirconia sintered body having a high sintered-body density and high strength and giving an excellent sense of translucency, without conducting any special sintering, such as HIP sintering. The invention relates to a technique for obtaining, through normal-pressure sintering, a translucent zirconia sintered body characterized by comprising zirconia which contains 2-4 mol % yttria as a stabilizer and has an alumina content of 0.2 wt % or lower, and by having a relative density of 99.8% or higher and a total light transmittance, as measured at a thickness of 1.0 mm, of 35% or higher. It is preferred that a powder containing 0-0.2 wt % alumina with a particle diameter of 0.01-0.5 μm, having a BET specific surface area of 5-16 m 2 /g and an average particle diameter of 0.3-0.7 μm, and having a rate of sintering shrinkage in normal-pressure sintering (Δρ/ΔT; g/cm 3 ·° C.) of 0.0125 or higher but 0.0160 or lower should be subjected to normal-pressure sintering in the atmosphere.

1 . A translucent zirconia sintered body characterized by comprising zirconia which contains 2-4 mol % yttria as a stabilizer and has an alumina content of 0.2 wt % or lower, and by having a relative density of 99.8% or higher and a total light transmittance, as measured at a thickness of 1.0 mm, of 35% or higher. 
     
     
         2 . The translucent zirconia sintered body as claimed in  claim 1  which has an alumina content of 0.1-0.2 wt %. 
     
     
         3 . The translucent zirconia sintered body as claimed in  claim 1  which has an alumina content lower than 0.1 wt %. 
     
     
         4 . The translucent zirconia sintered body as claimed in  claim 1  which contains no alumina. 
     
     
         5 . The translucent zirconia sintered body as claimed in  claim 1  which has a crystal grain diameter of 0.20-0.45 μm. 
     
     
         6 . The translucent zirconia sintered body as claimed in  claim 1  which has a monoclinic fraction of 30% or lower after 24-hour immersion in 140° C. hot water. 
     
     
         7 . The translucent zirconia sintered body as claimed in  claim 1  which has a three-point bending strength of 1,000 MPa or higher. 
     
     
         8 . A powder for a translucent zirconia sintered body, which is a powder containing 2-4 mol % yttria as a stabilizer, having an alumina content of 0.2 wt % or lower, and having a rate of sintering shrinkage (Δρ/ΔT; g/cm 3 ·° C.), in a relative-density range of 70% to 90% in normal-pressure sintering in the atmosphere at, 300° C./hr, of 0.0120 or higher but 0.0160 or lower. 
     
     
         9 . The powder for a translucent zirconia sintered body as claimed in  claim 8  which is a powder containing 2-4 mol % yttria as a stabilizer, containing 0.1-0.2 wt % alumina, and having a rate of sintering shrinkage (Δρ/ΔT; g/cm 3 ·° C.), in a relative-density range of 70% to 90% in normal-pressure sintering in the atmosphere at, 300° C./hr, of 0.0125 or higher but 0.0160 or lower. 
     
     
         10 . The powder for a translucent zirconia sintered body as claimed in  claim 8  which is a powder containing 2-4 mol % yttria as a stabilizer, containing less than 0.1 wt % alumina, and having a rate of sintering shrinkage (Δρ/ΔT; g/cm 3 ·° C.), in a relative-density range of 70% to 90% in normal-pressure sintering in the atmosphere at, 300° C./hr, of 0.0125 or higher but 0.0160 or lower. 
     
     
         11 . The powder for a translucent zirconia sintered body as claimed in  claim 8  which is a powder containing 2-4 mol % yttria as a stabilizer, containing no alumina, and having a rate of sintering shrinkage (Δρ/ΔT; g/cm 3 ·° C.), in a relative-density range of 70% to 90% in normal-pressure sintering in the atmosphere at, 300° C./hr, of 0.0120 or higher but 0.0135 or lower. 
     
     
         12 . A process for producing a translucent zirconia sintered body characterized by molding the zirconia powder as described in any one of  claims 8  to  11  and then sintering the resultant green body at 1,350-1,450° C. at normal pressure. 
     
     
         13 . A dental material comprising the sintered body as described in any one of  claims 1  to  7 . 
     
     
         14 . The dental material as claimed in  claim 13  which is a denture and/or a denture mill blank. 
     
     
         15 . The dental material as claimed in  claim 13  which is an orthodontic bracket.