Ceramic on zirconia base with aluminum oxide, spinel, mullite or spinel and mullite and with improved hydrothermal and thermal stability

摘要

The invention consists of zirconia base with high hydrothermal stability which:PP(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:PPF (88, 10, 2),PPG (89, 10, 1),PPL (93.5, 4, 2.5), PPM (93, 2, 5),PPN (88, 1, 11), and PPK (86, 1,13),PPand 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, andPP(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° 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°- 400° C.