Nonstoichiometry and relative stabilities of Y2Ti2O7 polar surfaces: A density functional theory prediction

The ferrite/oxide interface and helium management in nano-structured ferritic alloys from the first principles

“…The critical pO2 values for nonstoichiometric-to-stoichiometric transitions are marked as points a and b. Apparently, with increasing pO2, the most energetically favorable interface structure would change from the Y/Ti-rich to stoichiometric and then to the O-rich, following the same trend as seen for the Y2Ti2O7 (100) free surface [55]. But in contrast to the free surface results, the non-stoichiometric interfaces (both Y/Tiand O-rich) dominate here in a much wider range of pO2, leaving an extremely narrow range of pO2 (-28<ln pO2<-26) for preferentially forming a stoichiometric interface.…”

“…Given the OR and the interfacial strains, the stability of an interface structure is dictated by interfacial stoichiometry and interfacial coordination [53,54]. According to our previous study [55], a polar free surface of Y2Ti2O7 may have various possible chemical terminations, or stoichiometry, depending on the oxygen activity (expressed in term of oxygen partial pressure). Similarly, depending on the internal local oxygen activity, one of three typical stoichiometry types is selected on the oxide side of the ferrite/Y2Ti2O7 interface, namely the stoichiometric (labeled as stoi), the non-stoichiometric Y/Ti-rich (ns-2Y2Ti), and the non-stoichiometric O-rich type (ns-5O).…”

Recent Progress in Developing and Qualifying Nanostructured Ferritic Alloys for Advanced Fission and Fusion Applications

“…Note, interface vacancies in the iron may provide better lattice matching. The stoichiometry of the oxide termination surfaces has a large effect on their energies, 39 and it is expected that this, along with misfit strains and structural defects, will mediate the oxidematrix interface as well.…”

Radiation-sustained nanocluster metastability in oxide dispersion strengthened materials

“…These nano-particles are distinguished by their high stability and resistance to coarsening even at high temperature and, thus, have attracted considerable interest in the materials research community. Previous studies suggested that these nano-particles range from coherent solute-enriched clusters (1-3 nm in diameter) to non-and or near-stoichiometric complex oxide (more than 3 nm in diameter) [2]. Concerning the near-stoichiometric oxide particles, it is now well established that their structure matches with the Y 2 Ti 2 O 7 structure [2,3] or with the Y 2 TiO 5 structure [2], although they present a stoichiometry gap [4].…”

“…Previous studies suggested that these nano-particles range from coherent solute-enriched clusters (1-3 nm in diameter) to non-and or near-stoichiometric complex oxide (more than 3 nm in diameter) [2]. Concerning the near-stoichiometric oxide particles, it is now well established that their structure matches with the Y 2 Ti 2 O 7 structure [2,3] or with the Y 2 TiO 5 structure [2], although they present a stoichiometry gap [4]. However, these nano-particles are not of interest for this paper, only the solute-enriched clusters called nanoclusters hereafter are worthwhile.…”