Garnet stability in the Al–Ca–Mg–Si–Y–O system with implications for reactions between TBCs, EBCs, and silicate deposits

Eeshani Godbole, Nikhil Karthikeyan, David Poerschke

Research output: Contribution to journalArticlepeer-review

Abstract

This work expands the understanding of the garnet solid solution field in the yttria-calcia-magnesia-alumina-silica system. The crystal chemistry was used to define the theoretical extent of the garnet homogeneity range based on site-specific substitution rules and charge neutrality constraints. Compositions lying within this range were equilibrated at 1400°C. The resulting phase assemblages were analyzed to determine the identity and compositions of the equilibrium phases. Quantitative chemical analysis was used to infer that Mg2+ preferentially partitions into the intermediate-sized octahedral site compared to the larger dodecahedral site, that Ca2+ has a higher solubility in the dodecahedral site than Mg2+, and that the presence of Mg2+increases the total Si4+ solubility in the garnet structure. The results were also used to map the extent of the garnet solid solution phase field at 1400°C. The findings are discussed in the context of efforts to understand the interactions between Y-containing thermal and environmental barrier coatings and silicate deposits.

Original languageEnglish (US)
Pages (from-to)5270-5282
Number of pages13
JournalJournal of the American Ceramic Society
Volume103
Issue number9
DOIs
StatePublished - Sep 1 2020

Keywords

  • CMAS
  • environmental barrier coatings
  • garnet
  • rare earth
  • solid solution
  • thermal barrier coatings

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