Development of Nanoscale Ceramics for Advanced Power Applications

Bulk structures of unstabilized ZrO{sub 2-x}, with x in the range of 0 {<=} x {<=} 0.44, at ambient pressure have been found to exist in three different structures. (monoclinic, tetragonal and cubic.). At ambient temperature and elevated pressures above 3.5 GPa, unstabilized zirconia at these same compositions is found as a fourth phase, the orthorhombic phase. Work done in this project has demonstrated that nanoscale zirconia particles containing the orthorhombic phase in addition to amorphous material can be produced through solgel methods. Extensive characterization of this material including recent high temperature x-ray diffraction work has indicated that the structure of the synthesized zirconia appears to be linked to the oxygen vacancy population in the material, and that water appears to be a critical factor in determining the type of material formed during synthesis. These results suggest that surface energy alone is not the controlling factor in determining crystal phase