Issue 17, 2018

Phase diagram and oxygen–vacancy ordering in the CeO2–Gd2O3 system: a theoretical study

Abstract

We present the phase diagram of Ce1−xGdxO2−x/2 (CGO), calculated by means of a combined Density Functional Theory (DFT), cluster expansion and lattice Monte Carlo approach. We show that this methodology gives reliable results for the whole range of concentrations (xxGd ≤ 1). In the thermodynamic equilibrium, we observe two transitions: the onset of oxygen-vacancy (O–Va) ordering at ca. 1200–3300 K for concentrations xGd = 0.3–1, and a phase separation into CeO2 and C-type Gd2O3 occurring below ca. 1000 K for all concentrations. We also model ‘quenched’ systems, with cations immobile below 1500 K, and observe that the presence of random-like cation configurations does not prevent C-type vacancy ordering. The obtained transition temperatures for Va ordering agree rather well with existing experimental data. We analyse the effect of vacancy ordering and composition on the lattice parameters and relaxation pattern of cations.

Graphical abstract: Phase diagram and oxygen–vacancy ordering in the CeO2–Gd2O3 system: a theoretical study

Supplementary files

Article information

Article type
Paper
Submitted
13 Feb 2018
Accepted
04 Apr 2018
First published
05 Apr 2018

Phys. Chem. Chem. Phys., 2018,20, 11805-11818

Phase diagram and oxygen–vacancy ordering in the CeO2–Gd2O3 system: a theoretical study

P. A. Žguns, A. V. Ruban and N. V. Skorodumova, Phys. Chem. Chem. Phys., 2018, 20, 11805 DOI: 10.1039/C8CP01029C

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