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.
- environmental barrier coatings
- rare earth
- solid solution
- thermal barrier coatings