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US 4,303,447 AGranted
Low temperature densification of zirconia ceramics
AssigneeUniversity of Illinois Foundation
InventorsRelva C. Buchanan, H. Dale DeFord, Anup Sircar
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AssigneeUniversity of Illinois Foundation
InventorsRelva C. Buchanan, H. Dale DeFord, Anup Sircar
Estimating the term…
Addition of from about 1.0 to about 15% by weight of a vanadium oxide or boric oxide promoter to a zirconia (ZrO.sub.2) powder promotes rapid densification at temperatures below about 1300.degree. C. For example, a density of greater than 92% of estimated theoretical density can be achieved by addition of 4% by weight of ZrV.sub.2 O.sub.7 to monoclinic ZrO.sub.2 and sintering at 1100.degree. C. for about 24 hours. Sintering at temperatures below about 1150.degree. C. avoids the destructive monoclinic/tetragonal phase transformation and provides for better control of microstructure and composition. A density of greater than 98% of estimated theoretical density can be achieved by addition of from about 2 to about 5% by weight of a boric oxide promoter to stabilized cubic ZrO.sub.2 and sintering at about 1200.degree. C. for about 4 hours.
A fired ceramic composition having a density greater than about 98% of theoretical density which composition consists essentially of a major amount of zirconia and from about 1.0 to about 15% by weight of a boric oxide densification promoter wherein the boric oxide promoter is selected from the group consisting of calcium metaborate, calcium tetraborate, and B.sub.2 O.sub.3 ;
A fired ceramic composition having a density greater than about 90% of theoretical density and being substantially entirely in the monoclinic crystal configuration which composition is prepared by the steps of milling and blending a zirconia powder substantially entirely in the monoclinic crystal configuration with from about 1 to about 10% by weight of a vanadium oxide promoter having a melting point below about 1200.degree. C.;
A process for preparing a zirconia ceramic composition having a density greater than about 90% of theoretical density and being substantially entirely in the monoclinic crystal configuration comprising the steps of milling and blending a zirconia powder substantially entirely in the monoclinic crystal configuration with about from 1 to about 10% by weight of a vanadium oxide promoter having a melting point below about 1200.degree. C.;
A process for preparing a zirconia ceramic composition having a density greater than about 98% of theoretical density comprising the steps of milling and blending a zirconia powder, stabilized in the cubic crystal configuration with from about 5 to about 15% by weight of an oxide selected from the group consisting of CaO, MgO, and Y.sub.2 O.sub.3, with from about 1 to about 15% by weight of a boric oxide promoter having a melting point below about 1200.degree. C.;
Dependencies are inferred from the claim text.