July 1997 1683 2D. B. Marshall, J. J. Ratto, and F.F. "Enhanced Fracture Composites of Ce-Zro, and Z/onAgo ite.D.B. Marshall. "The Design of High Toughness Laminar Zirconia Compos- esistance Curves in Layered T/Ta annister andR J H. Hannink, Techn 1993 C J. Russo, M. P. Harme, H. M. Chan, and g. A. Miller. " Design of a ved Strength and tough rakash, P. Sarkar, and P. S. Nicholson, "Crack Deflection in Ceramic/ 28 Ak203 rO/A1,O, Micro-Laminate Ceramic/Ceramic Composites J. Mater. Sci. J S. Moya, " Layered Ceramic, "Adv Mater., 7. 185-89(1995). w.J. Clegg, K. Kendall, N. M. Alford, T. w. Button, and J. D. Birchall,"A =(E2·E'1(E2+E A J. Phillipps, w.J. Clegg, of fracture energies with debond He and Hutchinson. 2 Solid curve is debond criterion for tetragonal Liu and S. M. Hsu, Fracture Behavior of Multilayer Silicon Nitride/ zirconia layers(negligible residual stresses). Dashed curves are approxi JAm. Ceram.Soc,7992452-57(1996 mate criteria in the presence of residual stresses: (1)m=0. 15, corre- sponding to ZrO, layers that are transformed to the monoclinic structure Structural Applications" pre (residual compression in ZrO, layers, tension in LaPO, layers)and(2)m Ceramic Society, Cincinnati, OH, May 3, 1995, Joint Engineering the american 0.04 for ZrO2/Al,O, layers. Symbols represent measured properties for LaPO/Y-ZrO, and LaPO, /(Y-Zro2, Al,O3)systems P. E. D. Morgan and D. B Ma ize, and K is the applied stress intensity factor for the incident crack. For a composite with equal thickness layers of Lapo D H Kuo and w. m. Kriven, "Characterization of Yttrium Phosphate and O2 layers fully transformed, l stresses are as follows: zero normal to the layers: +800 D. H. Kuo and w. M. Kriven, ""Chemical Stability, Microstructure and MPa parallel to the layers within the ZrO2. Taking the charac- 23-34 19 avior of LaPo, Containing Ceramics,"Mater.SciEng.A,210 MPa parallel to the layers within the lapO. layers; and-800 teristic faw size to be equal to the grain size(-1 um)and K as P. E. D Morgan and D, B. Marshall, "Functional Interfaces in Oxide-Oxid the toughness of zirconia(6 MPa.m), we obtain m=+o15 ay, " Textured Magnetoplumbite Fiber-Matrix for a crack growing from transformed Zro2 to LaPO, and m Interphase Derived Sol-Gel Fiber Coatings, J. Am. Ceram Soc. 79 [5] 0.15 for a crack growing in the reverse direction. The corre- sponding positions of the critical debond conditions from the ment of Int M. H. Lewis, M. G. Cain, P Doleman, A.G. Razzell, and J Gent, Develop- results of He et al. 4 are shown as broken lines in Fig. 10. For Ceramic Transactions, Vol 58, High-Temperature Ceramic-Matrix Composites both directions of crack growth, the effect of residual stress l: Design, Durability, and Performance. American Ceramic Society, Westerville, makes the response already described more likely. (ii) Thermal Expansion Mismatch Stresses: As discussed He and J. w. hutchinson, "Crack Defection at an Interface between lids struci,25,1053-67(1989) sion mismatch are present in composites consisting of layers of Method for efficient colloidal Panic e Eckiange and D s Pearson. "New in the previous section, residual stresses due to thermal expan- Al2 O,ZrO2 and LapO,(these stresses are negligibly small in composites consisting only of zro2 and Lapo4). The sign of the and AL,O, /Zro, Composite Slurries vs Inter Al, O, to ZrO, ratio is-200 MPa, giving m=0.04. The corre sponding shift in the critical debond condition is shown in te" Pp. 543-53 in Proceedings of 5th Intemational Conference on Composite Fig. 10; the shift does not change the behavior described above WrA. G. Evans, "Engineering Property Requirements for High Performance materials. Metallurgical Society, Warrendale, PA, 1985. Ceramics, "Mater Sci Eng, 71, 3-21(1985) V. Conclusions hear Fracture, "Int. J fract. 37, 137-59(1988) Y-stabilized zirconia and Y-zro,/AL, O which is stable at tem- ed ineering Materials, ASTM STP 948 dited by J. E. Masters, American Society for Testing and Materials, West peratures at least as high as 1600'C. However, with Ce-stabilized ZrO,, counter diffusion of Ce and La produces a new pyrochlore- like phase. In the presence of two-phase Ce-ZrO2/AL,o3, the R. Anstis, P. Chantikul, B. R. Lawn, and D. B formation of a( La, Ce)magnetoplumbite was observed. Despite these reactions, multilayered composites exhibited debonding in the LapO4 layers when loaded in bending 2Z. Suo and J W. Hutchinson, "On Sandwich Test Specimens for Measuring Interface Crack Toughness, "Mater. Sci. Eng, A, 107, 135-43(1989) Acknowledgment: We wish to thank Dr. John Armstrong and Paul MS. Ho, C. Hillman, F. F. Lange, and Z. Suo, "Surface Cracking Carpenter for their assistance with the electron microprobe ler Biaxial Residual Compressive Stress "J. Am. Ceram. Soc. 78 [9]2353- Refere B.R. Lawn and E. R J. Fuller, ""Measurement of Thin-Layer Surface er, H. M. Chan, and G. A. Miller, "Unique Op Microstructural Engineering with Duplex and Laminar Ceramic P Compost s r Stres,ss b avis. pt. R. M. Housley, " Machin- JAm. Ceram.Soc,75]175-28(1992). 00. Muller and R. Roy. The Major Ternary Structural Families. Springer- MM.-Y He, A. G. Evans. and J. w, Hutchinson . Crack Deflection at Equation(2)is an approximate expression, valid as long as the elastic mismatch is similar elastic Materials: role of residual stresses ,l J. Solids struct.,31[24]3443-55(1994)July 1997 Debonding in Multilayered Composites of Zirconia and LaPO, 1683 ’D. B. Marshall, J. J. Ratto. and F. F. Lange. “Enhanced Fracture Toughness in Layered Composites of Ce-ZrO, and A1,0,,” J. Am. Ceram. Soc., 74 [12] ’D. B. Marshall, “The Design of High Toughness Laminar Zirconia Compos￾ites,” Am. Ceram. SOC. Bull., 71 [6] 969-73 (1992). ,D. B. Marshall and J. J. Ratto, “Crack Resistance Curves in Layered Ce-ZrO,/Al,O, Ceramics”; pp. 517-23 in Science and Technology of Zirconia V. Edited by S. P. S. Badwal, M. I. Bannister, and R. J. H. Hannink. Technomic, Lancaster, PA, 1993. ’C. J. Russo, M. P. Harmer, H. M. Chan, and G. A. Miller, “Design of a Laminated Ceramic Composite for Improved Strength and Toughness,” J. Am. Ceram. Soc., 75 [I21 3396-400 (1992). 60. Prakash. P. Sarkar. and P. S. Nicholson, “Crack Deflection in Ceramic/ Ceramic Laminates with Strong Interfaces,’’ J. Am. Ceram. Soc., 78 [ 141 1125- 27 (1995). ’P. S. Nicholson, P. Sarkar, and X. Haung, “Electrophoretic Deposition and Its Use to Synthesize ZrO,/Al,O, Micro-Laminate Ceramic/Ceramic Composites,’’ 2979-87 (1991). Fig. 10. Comparison of fracture energies with debonding criterion of He and Hutchinson.’” Solid curve is debond criterion for tetragonal zirconia layers (negligible residual stresses). Dashed curves are approxi￾mate criteria in the presence of residual stresses:” (1) q = 0.15. corre￾sponding to ZrO, layers that are transformed to the monoclinic structure (residual compression in ZrO, layers, tension in LaPo, layers) and (2) q = 0.04 for zrO,/Al,O, layers. Symbols represent measured properties for LaP04/Y-Zr0, and LaFQ4/(Y-Zr0,, AI,O,) systems. size, and K is the applied stress intensity factor for the incident crack.+ For a composite with equal thickness layers of LaPO, and ZrO,, and with the ZrO, layers fully transformed, the resid￾ual stresses are as follows: zero normal to the layers; +800 MPa parallel to the layers within the LaPO, layers; and -800 Mpa parallel to the layers within the ZrO,. Taking the charac￾teristic flaw size to be equal to the grain size (- 1 pm) and K as the toughness of zirconia (-6 MPa-m’”), we obtain q = +0.15 for a crack growing from transformed Zro, to LaPO, and q = -0.15 for a crack growing in the reverse direction. The corre￾sponding positions of the critical debond conditions from the results of He et aL3, are shown as broken lines in Fig. 10. For both directions of crack growth, the effect of residual stress makes the response already described more likely. (ii) Thermal Expansion Mismatch Stresses: As discussed in the previous section, residual stresses due to thermal expan￾sion mismatch are present in composites consisting of layers of Al,O,-ZrO, and LaPO, (these stresses are negligibly small in composites consisting only of ZrO, and LaPO,). The sign of the mismatch is the same as that of the tetragonal-to-monoclinic transformation. The magnitude of these stresses for the 1:l A1,0, to ZrO, ratio is -200 MPa, giving -q = 0.04. The corre￾sponding shift in the critical debond condition is shown in Fig. 10; the shift does not change the behavior described above. V. Conclusions Lanthanum phosphate forms a weakly bonded interface with Y-stabilized zirconia and Y-Zro,/Al,O,, which is stable at tem￾peratures at least as high as 1600°C. However, with Ce-stabilized Zro,, counter diffusion of Ce and La produces a new pyrochlore￾like phase. In the presence of two-phase Ce-ZrO,/Al,O,, the formation of a (La,Ce) magnetoplumbite was observed. Despite these reactions, multilayered composites exhibited debonding in the LaPO, layers when loaded in bending. Acknowledgment: We wish to thank Dr. John Armstrong and Paul Carpenter for their assistance with the electron microprobe measurements. References ‘M. P. Harmer, H. M. Chan, and G. A. Miller, “Unique Opportunities for Microstructural Engineering with Duplex and Laminar Ceramic- Composites,” J.Am. Ceram. SOC., 75 [7] 1715-28 (1992). ‘Equation (2) is an approximate expression, valid as long as the elastic mismatch is not too large.u J. Marer.-Sci., 28,6274178 (1993). ‘5. S. Moya, “Layered Ceramic,” Adv. Mazer., 7,185-89 (1995). W. J. Clegg, K. Kendall, N. M. Alford, T. W. Button, and J. D. Birchall. “A Simple Way to Make Tough Ceramics,”Nature (London), 347,455-57 (1990). ‘‘A. J. Phillipps, W. J. Clegg, and T. W. Clyne, “The Correlation of Interfacial and Macroscopic Toughness in SIC Laminates,” Composites, 24 [2] 166-76 (1993). “H. Liu and S. M. Hsu, “Fracture Behavior of Multilayer Silicon Nitride/ Boron Nitride Ceramics:’J. Am. Ceram. Soc., 79 [9] 2452-57 (1996). ”J. B. Davis and W. J. Clegg, “Ceramic Laminates for High Temperature Structural Applications”; presented at the 97th Annual Meeting of the American Ceramic Society, Cincinnati, OH, May 3, 1995. Joint Engineering Ceramics and Basic Science Divisions (Paper No. C-37-95). ”P. E. D. Morgan and D. B. Marshall, “Ceramic Composites of Monazite and Alumina,”J. Am. Cerum. Soc., 78 [6] 1553-63 (1995). I4P. E. D. Morgan, D. B. Marshall, and R. M. Housley, “High Temperature Stability of MonaziteAlumina Composites,” J. Mater. Sci. Eng. A, 195, 215- 22 (1995). I5D.-H. Kuo and W. M. Kriven, “Characterization of Yttrium Phosphate and a Yttrium Phosphateflttrium Aluminate Laminate,” J. Am. Cerum. SOC.. 78 [ 111 3121-24 (1995). I6D.-H. Kuo and W. M. Kriven, “Chemical Stability, Microstructure and Mechanical Behavior of LaFQ-Containing Ceramics,” Mater. Sci. Eng. A, 210, 123-34 (1996). ”F! E. D. Morgan and D. B. Marshall, “Functional Interfaces in Oxide-Oxide Composites,”J. Marer. Sci. Eng. A, 162 [l-21 15-25 (1993). I’M. K. Cinibulk and R. S. Hay, “Textured Magnetoplumbite Fiber-Matrix Interphase Derived Sol-Gel Fiber Coatings,’’ J. Am. Ceram. Soc., 79 [5] 1233- 46 (1996). I’M. H. Lewis, M. G. Cain, P. Doleman, A. G. Razzell, and J. Gent, “Develop￾ment of Interfaces in Oxide and Silicate-Matrix Composites”; pp. 41-52 in Ceramic Transactions, Vol. 58, High-Temperature Ceramic-Matrix Composites I: Design, Durabiliry. and Petformanre. American Ceramic Society, Westerville, OH, 1995. ”M.-Y. He and J. W. Hutchinson, “Crack Deflection at an Interface between Dissimilar Materials,” Inr. J. Solids Strucr., 25, 1053-67 (1989). 21B. V. Velamakanni, J. C. Chang, F. F. Lange. and D. S. Pearson, “New Method for Efficient Colloidal Particle Packing via Modulation of Repulsive Lubricating Hydration Forces,” Langmuir, 6 [7] 1323-25 (1990). 22J. C. Chang and B. V. Velamakanni, “Centrifugal Consolidation of A1,0, and Al,O,/ZrO, Composite Slurries vs Interparticle Potentials: Particle Packing and Mass Segre.gation,”J. Am. Ceram. Soc., 74 [9] 2201-204 (1991). 23A. G. Evans, M. D. Thouless, D. P. Johnson-Walls, E. Y. Luh. and D. B. Marshall, “Some Structural Properties of Ceramic Matrix Fiber Compos￾ite”; pp. 543-53 in Proceedings of 5th International Conference on Composite Materials. Metallurgical Society. Warrendale, PA, 1985. ”A. G. Evans, “Engineering Property Requirements for High Performance Ceramics,”Marer. Sci. Eng., 71.3-21 (1985). 25H. Chai, “Shear Fracture,” Inr. J. Frucr.. 37, 137-59 (1988). z6M. F. Hibbs and W. L. Bradley, “Correlations between Micromechanical Failure. Processes and the Delamination Toughness of Graphite Epoxy Systems”; pp. 68-97 in Fracrography of Modern Engineering Materials, ASTM STP 948. Edited by J. E. Masters. American Society for Testing and Materials, West Conshohoken, PA, 1987. ,’B. W. Smith and R. A. Grove, “Determination of Crack Propagation Direc￾tions in Graphite Epoxy Structures”; see Ref. 26, pp. 68-97. %. R. Anstis, P. Chantikul, B. R. Lawn, and D. B. Marshall, “A Critical Evaluation of Indentation Techniques for Measuring Fracture Toughness: I. Direct Crack Measurements,”J. Am. Ceram. Soc., 64 [9] 533-38 (1981). 29Z. Suo and J W. Hutchinson. “On Sandwich Test Specimens for Measuring Interface Crack Toughness,”Murer. Sci. Eng. A, 107, 135-43 (1989). ’OS. Ho, C. Hillman, F. F. Lange, and 2. SUO, “Surface Cracking in Layers under Biaxial Residual Compressive Stress,” J. Am. Ceram. Soc., 78 [9] 2353- 59 (1995). ”B. R. Lawn and E. R. J. Fuller, “Measurement of Thin-Layer Surface Stresses by Indentation Fracture:’J. Marer. Sci.. 19,4061-67 (1984). ’3. B. Davis, D. B. Marshall, P. E. D. Morgan, and R. M. Housley, “Machin￾able Ceramics Based on LaPO, and CePO,,” unpublished work. ”0. Muller and R. Roy, The Major Ternary Srrucrural Families. Springer￾Verlag, New York, 1974. ’,M.-Y. He, A. G. Evans, and J. W. Hutchinson, “Crack Deflection at an Interface between Dissimilar Elastic Materials: Role of Residual Stresses,” Inr. J. Solids Strucr., 31 [24] 3443-55 (1994). 0