Characterization of un-stabilized orthorhombic zirconia synthesized at ambient temperature and pressure

Bulk structures of un-stabilized ZrO _2-x with x in the 0 ≤ x ≤ 0.44 range under ambient pressure exist in three different structures (monoclinic, tetragonal and cubic). At ambient temperature and elevated pressures above 3.5 GPa, zirconia, at these compositions, a fourth phase is found, the orthorhombic structure. A dilute sol-gel method was used to produce nanoscale zirconia particles containing the unstabilized orthorhombic cotunnite structure for use in this project. Extensive characterization of this material indicates that the critical factor in determining the synthesized structures appears to be the number and placement of oxygen vacancies. These results also indicate that surface energy alone is not the controlling factor in determining the crystal structure synthesized.