W0239

Strain Charaterization on 3YTZ-Al₂O₃ Composites. M. Mir, J.-C. M’Peko, M.F. De Souza and Y.P. Mascarenhas, Institute of Physics at São Carlos, Univ. of São Paulo, C. Postal: 369, 13560-970, São Carlos – SP, Brazil.

The microstructural characteristics of zirconia-alumina composites were studied in this work over a wide range of compositions. The two-phase system was prepared following the standard ceramic method, and starting from commercial yttria-stabilized zirconia (3YTZ, Tosoh, Japan) and alumina (AKP-50 Sumitomo, Japan) powders, the former being calcined prior to forming the composites. Volume fractions of 10, 20, 40, 60, 80 and 100 % of 3YTZ were considered. The final microstructure features of such composites were analyzed by scanning electron microscopy (SEM). Internal stress effects are postulated to derive from the alumina sintering on the calcined zirconia during final heat treatment. For monitoring the behavior of such effects upon variation of zirconia volume fraction, diffraction data of all the prepared ceramic samples were measured by Bragg-Bentano X-ray diffractometry (XRD). The Rietveld analysis method was subsequently applied. The evaluation of the resulting strain effects was based on (i) the refinement of the peak profile shape using multi-line (the Rietveld method) and single-line and (ii) the variations of the final zirconia cell parameters. The present work strongly suggests the importance of considering the difference in thermal shrinkage of mixed phases when attempting to produce stress-free composite materials.

Acknowledgments

M. Mir thanks the Centro Latino Americano de Física for a grant. M’Peko acknowledges the support from the Brazilian research funding FAPESP through grant n^o. 2000/04460-6. Y.P. Mascarenhas thanks CNPq for a research fellowship.