Local structures surrounding Zr in nanostructurally stabilized cubic zirconia: Structural origin of phase stability

Abstract

Local environment surrounding Zr atoms in the thin films of nanocrystalline zirconia ͑ZrO 2 ͒ has been investigated by using the extended x-ray absorption fine structure ͑EXAFS͒ technique. These films prepared by the ion beam assisted deposition exhibit long-range structural order of cubic phase and high hardness at room temperature without chemical stabilizers. The local structure around Zr probed by EXAFS indicates a cubic Zr sublattice with O atoms located on the nearest tetragonal sites with respect to the Zr central atoms, as well as highly disordered locations. Similar Zr local structure was also found in a ZrO 2 nanocrystal sample prepared by a sol-gel method. Variations in local structures due to thermal annealing were observed and analyzed. Most importantly, our x-ray results provide direct experimental evidence for the existence of oxygen vacancies arising from local disorder and distortion of the oxygen sublattice in nanocrystalline ZrO 2 . These oxygen vacancies are regarded as the essential stabilizing factor for the nanostructurally stabilized cubic zirconia.

Impact of the Oxygen Defects and the Hydrogen Concentration on the Surface of Tetragonal and Monoclinic ZrO2 on the Reduction Rates of Stearic Acid on Ni/ZrO2

“…12. This peak shift from 3.3 to 3.0 Å is also related to a decreasing symmetry as varying from the tetragonal to the monoclinic phase 11a…”

Oxygen vacancy mediated cubic phase stabilization at room temperature in pure nano-crystalline zirconia films: a combined experimental and first-principles based investigation

“…Table 2. In bulk cubic zirconia, zirconium has 8 nearest neighboring oxygen atoms at a mean distance of 2.204 Å followed by 12 zirconium next nearest neighbor atoms at a mean distance of 3.599 Å [20]. It is immediately apparent that the S3 film, which exhibits long film.…”

“…It is, therefore, worth mentioning two important points here from these previous studies: (i) the presence of implanted nitrogen in the films (in Ref. [20]) and (ii) the implanted nitrogen may also play a role (along with the oxygen vacancies) in the stabilization of the cubic phase.…”

Lattice distortions and oxygen vacancies produced in Au+-irradiated nanocrystalline cubic zirconia

“…These films have previously been shown to be structurally stable up to temperatures of 1123 K [5,10]. The films were then irradiated with 2 MeV Au + ions at a temperature of 160 or 400 K over a range of doses up to $35 displacements per atom (dpa).…”

“…The cubic phase is the most interesting phase as an engineering material due to its isotropic expansion at various temperatures. By doping the zirconia with an aliovalent compound with concentrations of $8-10 mol.% [1][2][3][4][5], the cubic phase of zirconia is stabilized at the temperatures typically experienced during the operation of oxygen sensors and fuel cells through the introduction of structural oxygen vacancies into the lattice. Secondly, the oxygen vacancies that serve to stabilize the zirconia also lead to the fast oxygen ion conductivity desired in many applications [2,3].…”