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Size and shape of oxygen vacancies and protons in acceptor-doped barium zirconate

Erik Jedvik (Institutionen för teknisk fysik, Material- och ytteori) ; Anders Lindman (Institutionen för teknisk fysik, Material- och ytteori) ; Magnús Pór Benediktsson (Institutionen för teknisk fysik, Material- och ytteori) ; Göran Wahnström (Institutionen för teknisk fysik, Material- och ytteori)
Solid State Ionics (0167-2738). Vol. 275 (2015), p. 2-8.
[Artikel, refereegranskad vetenskaplig]

The defect induced chemical expansion in acceptor-doped barium zirconate is investigated using density-functional theory (DFT) calculations. The two defect species involved in the hydration reaction, the +2 charged oxygen vacancy and the proton interstitial forming a hydroxide ion, are considered both as free defects and in association with the dopants Y, In, Sc and Ga. The defect induced strain tensor lambda is introduced, which provides a natural generalisation of the ordinary chemical expansion to three dimensions and to anisotropic distortions. Both the addition of a vacancy and a proton cause anisotropic distortions and a net contraction of the lattice, indicating that both the vacancy and the hydroxide ion are smaller than the oxygen ion. The contraction is considerably larger for the vacancy and the net effect in hydration, when a vacancy is filled and two protons are added, is an expansion, consistent with the experimental findings. The effect of the dopants on the chemical expansion in hydration is found to be quite small, even if it is assumed that both the vacancy and the proton are fully associated with a dopant atom in the lattice.

Nyckelord: BaZrO3, Density-functional theory, Oxygen vacancy, Proton, Chemical expansion, Hydration



Denna post skapades 2015-06-26. Senast ändrad 2016-10-17.
CPL Pubid: 218970

 

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Institutioner (Chalmers)

Institutionen för teknisk fysik, Material- och ytteori (1900-2015)

Ämnesområden

Fysikalisk kemi

Chalmers infrastruktur