Journal
CERAMICS INTERNATIONAL
Volume 47, Issue 11, Pages 15023-15029Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.ceramint.2021.02.058
Keywords
First principles calculations; Hafnates; Point defects; Formation energies
Categories
Funding
- Natural Science Foundation of Shanghai [20ZR1419200]
- Program for Professor of Special Appointment (Eastern Scholar) by Shanghai Municipal Education Commission [TP2015040]
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The composition-dependent point defect types and formation energies of RE2Hf2O7 were systematically investigated by first-principles calculations, revealing different dominant defect complexes under stoichiometric and non-stoichiometric conditions. The migration energy barriers for oxygen ions in pyrochlore hafnates were calculated, suggesting potential oxygen ionic conductivity and proposing a defect engineering strategy based on the findings.
In this work, the composition-dependent point defect types and formation energies of RE2Hf2O7 (RE = La, Ce, Pr, Nd, Pm, Sm, Eu and Gd) as well as the oxygen diffusion behavior are systematically investigated by firstprinciples calculations. The possible defect reactions and dominant defect complexes under stoichiometric and non-stoichiometric conditions are revealed. It is found that O Frenkel pairs are the predominant defect in stoichiometric pyrochlore hafnates. Hf-RE cation anti-site defects, accompanied by RE vacancies and/or oxygen interstitials, are stable in the non-stoichiometric case of HfO2 excess. On the other hand, RE-Hf anti-site defects together with oxygen vacancies and/or RE interstitials are preferable in the case of RE2O3 excess. The energy barriers for the migration along the VO48f - VO48f pathway of pyrochlore hafnates were calculated to be between 0.81 eV and 0.89 eV. Based on these results, a defect engineering strategy is proposed and the pyrochlore hafnates investigated here are predicted to exhibit potential oxygen ionic conductivity.
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