EVALUATION OF ULTRASONICALLY DETERMINED ELASTICITY-POROSITY RELATIONSIN ZINC-OXIDE

Ultrasonically determined elastic moduli in ZnO samples sintered to va rious densities were evaluated using both an empirical model and the M ori-Tanaka effective field theory. Both approaches have been successfu lly used to model the modulus-porosity relations in several material s ystems. In the present investigation, application of the empirical mod el predicted elastic moduli which deviated significantly from the expe rimental results. The deviation was attributed to the porosity depende nce of Poisson's ratio which was neglected in this model. When this de pendence was accounted for empirically, the fit to the experimental da ta was improved dramatically. Analysis of the data in the context of t he Mori-Tanaka model indicates that the porosity shape changes signifi cantly during the sintering process. This analysis may provide a conve nient way to quantitatively compare such changes for ceramic materials prepared by different processing techniques, such as by conventional and microwave sintering.