THE MICROSTRUCTURAL EVOLUTION OF ZIRCONIA CERAMICS DURING SINTERING

ZrO2-3mol%Y2O3 powders were pressed uniaxially using loads of 51 MPa and isothermal sintered at 1275OC. Measurements of the pore size, grain size and pore distribution indicated that contrary to the assumption of the phenomenological models of sintering, pore elimination was involved in densification and coarsening during the intermediate stage sintering. SEM imaging showed that many triple points did not contain pores. Thus the pore separation rather than the grain size should correlate with diffusion length. Pore boundary tessellation showed that the elimination of fine pores resulted in a heterogeneous microstructure in intermediate stage sintering containing regions of high solid volume fraction (>0.9). Higher pressing pressure (238 MPa) or higher sintering temperature (1315 OC) resulted in a higher densification rate and microstructural heterogeneity over a larger length scale