Role of zirconia addition in pore development and grain growth in alumina compacts

The role of 12.4 vol% ZrO2 addition in the microstructure evolution of alum ina compacts during the intermediate and final stages of sintering was inve stigated by means of small-angle neutron scattering measurements and stereo logical analysis. Both the pore-size evolution results and the grain-growth data indicate a narrowly defined onset density for the transition to the f inal sintering stage. The presence of ZrO2 as a second phase apparently mai ntains the stability of the intermediate sintering stage out to significant ly higher density than in single-phase alumina and plays an important role in inhibiting grain growth and in preventing pore-grain boundary separation . The influence of the ZrO2 second phase on pore evolution, grain growth, a nd sinterability of the alumina-zirconia composite is discussed and compare d to the behavior of single-phase alumina. The samples were prepared from c ommercially available powders, with naturally occurring porosity distributi ons, rather than from artifact (model) pore compacts prepared from nominall y pure research-grade materials. The goal was to gain an improved understan ding of microstructure development in real materials.