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Abstract

The invention consists of zirconia base with high hydrothermal stability which: (a) consists essentially of at least 40 weight % of partially stabilized zirconia of the ZrO.sub.2 -Y.sub.2 O.sub.3 -CeO.sub.2 system wherein the proportion of ZrO.sub.2, Y.sub.2 O.sub.3, and CeO.sub.2 is within the range defined by the line connecting points F, G, L, M, N and K in a ternary diagram (ZrO.sub.2, YO.sub.1.5, CeO.sub.2), the vertices of said points being given by the following molar % of ZrO.sub.2, YO.sub.1.5, and CeO.sub.2, respectively: F (88, 10, 2), G (89, 10, 1), L (93.5, 4, 2.5), M (93, 2, 5), N (88, 1, 11), and K (86, 1,13), and 3 to 60 weight % of at least one of Al.sub.2 O.sub.3, MgO.Al.sub.2 O.sub.3, spinel and mullite, and (b) has a mean crystal grain size not exceeding 2 micrometers and a bending strength of at least 100 kgf/mm.sup.2, said ZrO.sub.2 containing a minimum of 50 volume % tetragonal crystal structure and a maximum of 5 volume % monoclinic crystal structure when tested in steam of 180.degree. C. and 10 atm for 10 hours. The monoclinic crystal structure does not exceed 5 volume % when tested in an atmosphere of 300.degree. C. for 3000 hours. These zirconia base ceramics are stable in the presence of moisture under low temperatures of approximately 200.degree.-400.degree. C.

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First Claim