Grain-boundary-dependent segregation and phase separation in ceria–zirconia from atomistic simulation

Tom L. Underwood, Susanna Vigorito, Marco Molinari, John Purton, Nigel B. Wilding, John T.S. Irvine, Stephen C. Parker

Research output: Contribution to journalArticlepeer-review

Abstract

Doping is the most common strategy employed in the development of new and improved materials. However, predicting the effects of doping on the atomic-scale structure of a material is often difficult or limited to high-end experimental techniques. Doping can induce phase separation in a material, undermining the material's stability. A further complication is that dopant atoms can segregate to interfaces in a material such as grain boundaries (GBs), with consequences for key macroscopic properties of the material such as its conductivity. Here, we demonstrate a computational methodology based on semi-grand canonical Monte Carlo which can be used to probe these phenomena at the atomic scale for metal oxide solid solutions. The methodology can provide precise predictions of the thermodynamic conditions at which phase separation occurs. It can also provide the segregation patterns exhibited by GBs at given conditions. We apply the methodology to one of the most important catalytic materials, ceria–zirconia. Our calculations reveal an interesting richness in the GB segregation in this system. Most GBs we examined exhibited continuous increases in Zr segregation upon Zr doping, with a concomitant reduction in the formation enthalpies of the GBs. However, a few GBs exhibited no segregation at low temperatures. We also observed evidence of first-order complexion transitions in some GBs.

Original languageEnglish
Article number119872
Number of pages10
JournalActa Materialia
Volume271
Early online date28 Mar 2024
DOIs
Publication statusE-pub ahead of print - 28 Mar 2024

Data Availability Statement

The workhorse for our calculations was the open-source Monte Carlo simulation program DL_MONTE [67], [68]. Data pertaining to this work, including input and output files for our DL_MONTE simulations and scripts to perform data analysis and generate figures, are provided at [81].

Keywords

  • Grain boundary energy
  • Grain boundary segregation
  • Grain boundary structure
  • Monte Carlo simulation
  • Phase diagram calculation

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys

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