Substitutional doping and oxygen vacancies in La2Zr2O7 pyrochlore oxide
Artikel i vetenskaplig tidskrift, 2011

Density-functional calculations have been combined with thermodynamic modeling to study substitutional aacceptor dopants and oxygen vacancies in La2Zr2O7 pyrochlore oxide in equilibrium with an oxygen-containing atmosphere. Dilute-limit relative formation energy and corresponding relative concentration with respect to site selectivity and charge state have been calculated for twelve di- and trivalent dopants (Ba, Ca, Mg, Sr, Yb; In, Ga, Al, Nd, Gd, Sc, Y) incorporated on the La- and Zr sites. Similarly, the formation energy of oxygen vacancies has been calculated, as well as dopant--vacancy pair interaction energies. The study showed that site selectivity of the dopants is correlated to dopant size while on-site charge state is largely determined by valence of the dopant and host cation. Furthermore, formation of oxygen vacancies at atmospheric oxygen partial pressure was shown to be expected only in acceptor-doped samples at elevated temperatures. According to the results, vacancies will then form predominantly on oxygen sites in crystallographic positions 48f due to greater lattice relaxation compared to vacancy formation on the 8b site. In the pair interaction between vacancies and dopants the results showed generally stronger vacancy attraction for dopants on the Zr site compared to the La site and correlation between dopant size and interaction strength was seen. In particular the importance of elastic mechanisms is pointed out. Finally, the effects of the substitutional doping on the concentration and mobility of oxygen vacancies is discussed.

Defect clusters

Oxygen vacancies

Proton conductors

La2Zr2O7

Point defects

Doping

First-principles calculations

Pyrochlore oxides

DFT

Författare

Joakim Nyman

Chalmers, Teknisk fysik, Material- och ytteori

Mårten Björketun

Chalmers, Teknisk fysik, Material- och ytteori

Göran Wahnström

Chalmers, Teknisk fysik, Material- och ytteori

Solid State Ionics

0167-2738 (ISSN)

Vol. 189 19-28

Drivkrafter

Hållbar utveckling

Ämneskategorier

Annan fysik

Den kondenserade materiens fysik

Styrkeområden

Materialvetenskap

DOI

10.1016/j.ssi.2011.01.013