Work

Effects of Ca/Mg/Al/Si oxide additions on the phase stability of yttrium-iron garnets

Year: 2025

Type: article

Abstract: Rare-earth-containing garnets are important phases that evolve during the interaction of thermal and environmental barrier coatings (T/EBCs) with molten silicates (generically known as CMFAS). Notwithstanding their critical role, the chemical complexity of the garnet phase challenges an understanding of the phase equilibria and a description of their underlying thermodynamics. This study systematically examined substitutions of Ca, Mg, and Si into Y 3 Fe 5 O 12 and Y 3 (Fe 0.25 Al 0.75 ) 5 O 12 at 1400 °C. The results are compared to a similar study on substitutions into Y 3 Al 5 O 12 . The collective findings reveal that the Fe:Al ratio of the system is a key parameter for moderating the solubility of Ca and Si in the garnet phase. While the total Mg solubility is generally unaffected by Fe:Al ratio, the latter does alter the partitioning of Mg across the dodecahedral and octahedral sites. These solubility changes generally stabilize garnet, with decreased formation of secondary phases, notably apatite . Implications for T/EBC design are discussed.

Source: Journal of the European Ceramic Society

DOI: 10.1016/j.jeurceramsoc.2025.117278

Authors: Collin S. Holgate, Rodrigo E. Rodriguez, Sarah M. Miller, Eeshani Godbole, David L. Poerschke, Carlos G. Levi

Institutions: University of California, Santa Barbara, University of Minnesota

Language: English

Topic: High-Temperature Coating Behaviors

Subfield: Aerospace Engineering

Field: Engineering

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $3,900

Funders: National Science Foundation, University of California, Santa Barbara, Office of Naval Research