FRACTURE OF MULTILAYER OXIDE COMPOSITES

Ceramics with high strength and damage tolerance have been realized in the well-recognized non-oxide systems, e.g. silicon carbide/graphite and silicon carbide/boron nitride laminates. All-oxide systems without compliant materials functioning as do graphite and boron nitride are still facing the problem of catastrophic failure. In this study, ten k inds of multilayered, all-oxide laminates fabricated by a low-cost tap e casting technique were evaluated. These materials were yttrium phosp hate (YPO4)- and lanthanum phosphate (LaPO4)-containing zirconia (ZrO2 ) laminates, and aluminum phosphate (AlPO4)-containing alumina (Al2O3) laminates. A YPO4-containing ZrO2 laminate demonstrated excellent str ength and improved damage tolerance. A LaPO4-containing ZrO2 laminate also displayed a satisfactory result. An AlPO4/Al2O3 laminate was weak . The AlPO4/Al2O3 laminate was strengthened by reinforcing AlPO4 layer s with Al2O3, while retaining non-brittle fracture. Different flexural behaviors in different oxide laminates were discussed. (C) 1998 Elsev ier Science S.A.