Vol. 38. No. 1 LAYERED COMPOSITES TABLE I Sample Fr(MPa) Kc(MPa×m2) 50± 5.0±0.5 lumina/ 600±50 The bending test was made keeping the alumina-t-ZrO, layer in tension E 21 here E is Youngs modulus of the alumina layer and v is Poisson coefficient. Considering that Ae is 2.5X10>(Fig. 4), this residual stress was calculated to be 0.6 GPa. This residual stress value justifies the cracking observed in the alumina layers Fig 5 shows the SEM micrograph of the polished cross-section of alumina/alumina(Y-TZP) laminates. In this particular case, the thermal expansion of zirconia-containing layer is only slightly higher( Fig. 4)than the alumina layer, consequently a crack-free dense(99.8% th) laminated compact is obtained. a remaining porosity formed by small pores(- l um)located at alumina grain boundaries is observed at the alumina layers. The average grain size of the Y-TZP containing layers is 3 um Conversely in the alumina layer the average grain size is 40 um(Fig. 6). This laminate composite has both high strength(or"600 MPa) and a duplex grain size structure It is known that coarse ceramic microstructure ensures a good high temperature creep behavior ccording to Nabarro-Herring equation the creep rate, E-1/d- and according to Raj(4)the crack propagation rate da/dt-Idd being the main grain size of the ceramic compacts. That is, the alumina layers with coarse grain size may contribute to keep a high creep resistance in this laminate. Conversely the Y-TZP containing layers could provide high toughness and high bending strength to the layered The results obtained in the present investigation show that the sequential slip casting is a promising processing route to design microarchitectures with duplex grain size structure(3/40 um) and high bending strength (-600MPa)which can be considered as a potential material for high temperature structural applications. Tensile fatique testing and high temperature creep testing is in progress Acknowlegments Work supported by CICYT Spain under contract No. MAT91-0878. APT Research supported by irector, Office of Energy Research of U.S. Dept. of Energy under Contract No. DE-AC03-76SF00098 References 1. K Ni 2.M.P er. H. M. Chan and G. A Miller, J. Am. Ceram. Soc. 75, 1715(1992 A. J. Sanchez-Herencia R. Moreno, P. Pena and J. Requena, in Layered Ceramics, Proceedings of Third Euro-Ceramics, Vol. 3. Pp. 289-300, ed. P. Duran, Faenza, Edetrice 4. R. Raj, J Am Ceram Soc. 76, 2147(1993) 5. J Requena, R. M and J S. Moya, J. Am. Ceram. Soc. 72, 1511(198 6. R.C. Garvie and P. S, Nicholson, 55, 303(1972