Jump to main content
Jump to site search

Issue 4, 2014
Previous Article Next Article

Hydrogen defects in tetragonal ZrO2 studied using density functional theory

Author affiliations

Abstract

In the energy-structure paradigm, we analyzed the defects that can arise in tetragonal zirconium oxide (T-ZrO2) involving the hydrogen atom or the hydrogen molecule using density functional theory. Our results indicate that the dominant hydrogen defect under reducing conditions is Image ID:c3cp54153c-t1.gif, a complex formed between the hydride ion and a doubly charged oxygen vacancy. This result is consistent with the experimental observation that under reducing conditions, the solubility of hydrogen is proportional to the degree of hypostoichiometry of T-ZrO2. Under oxidizing conditions we found three different hydrogen defects, each predominating in a specific range of the chemical potential of electrons. Starting from the valence band top toward the conduction band bottom, these defects are the interstitial proton, Image ID:c3cp54153c-t2.gif, a complex formed between two hydrogen species and a zirconium vacancy with a net effective charge of (2−), Image ID:c3cp54153c-t3.gif, and finally a complex similar to the latter but with a net effective charge of (4−), Image ID:c3cp54153c-t4.gif. In Image ID:c3cp54153c-t5.gif the two hydrogens exist in the form of hydroxyl groups, while in Image ID:c3cp54153c-t6.gif they exist in the form of a hydrogen molecule. In addition, we found that up to three hydrogen species can favorably accumulate in a zirconium vacancy under oxidizing conditions. The clustering of hydrogen in cation vacancies can be a precursor for the deleterious effects of hydrogen on the mechanical properties and stability of metal oxides, in analogy with hydrogen embrittlement in metals. Finally we observed a red-shift and a blue-shift for the vibrational frequencies of all the hydroxyl groups and all the hydrogen molecules, respectively, in T-ZrO2 when compared to the gas phase frequencies. This is an important characteristic for guiding future experimental efforts to detect and identify hydrogen defects in T-ZrO2. The insights presented in this work advance our predictive understanding of the degradation behavior of T-ZrO2 as a corrosion resistant passive layer, as a gate dielectric and in biomedical applications.

Graphical abstract: Hydrogen defects in tetragonal ZrO2 studied using density functional theory

Back to tab navigation

Supplementary files

Publication details

The article was received on 01 Oct 2013, accepted on 11 Nov 2013 and first published on 11 Nov 2013


Article type: Paper
DOI: 10.1039/C3CP54153C
Citation: Phys. Chem. Chem. Phys., 2014,16, 1354-1365
  •   Request permissions

    Hydrogen defects in tetragonal ZrO2 studied using density functional theory

    M. Youssef and B. Yildiz, Phys. Chem. Chem. Phys., 2014, 16, 1354
    DOI: 10.1039/C3CP54153C

Search articles by author

Spotlight

Advertisements