Phase equilibria and crystal chemistry in the calcia-silica-yttria system

David L. Poerschke; Talia L. Barth; Olga Fabrichnaya; Carlos G. Levi

doi:10.1016/j.jeurceramsoc.2016.01.046

Phase equilibria and crystal chemistry in the calcia-silica-yttria system

David L. Poerschke, Talia L. Barth, Olga Fabrichnaya, Carlos G. Levi

Chemical Engineering and Materials Science

Research output: Contribution to journal › Article › peer-review

46 Scopus citations

Abstract

The phase equilibria in the CaO-SiO₂-Y₂O₃ system have been assessed at 1400 °C and 1600 °C using powders prepared by precipitation from precursors. Four ternary phases were identified: Ca/Y-cyclosilicate (Ca₃Y₂Si₆O₂₆), silico-carnotite (Ca₃Y₂Si₃O₁₂), cuspidine (nominally Ca₂Y₂Si₂O₉), and apatite (solid solution based on Ca₂Y₈Si₆O₂₆). The melting temperature of each ternary phase was measured and the shape of the liquid field at 1600 °C was assessed. The study emphasizes understanding the extent and crystallographic origin of the solid solution homogeneity range for apatite between Ca_0.5Y₉(SiO₄)₆O₂ and Ca_2.5Y_7.5(SiO₄)₆O_1.75, deviations from the nominal cuspidine stoichiometry, and solubility of Y₂O₃ in the high-temperature α-Ca₂SiO₄ polymorph. The results are discussed in the context of molten silicate (CMAS) degradation of thermal and environmental barrier coatings (T/EBCs).

Original language	English (US)
Pages (from-to)	1743-1754
Number of pages	12
Journal	Journal of the European Ceramic Society
Volume	36
Issue number	7
DOIs	https://doi.org/10.1016/j.jeurceramsoc.2016.01.046
State	Published - Jun 1 2016

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Publisher Copyright:
© 2016 Elsevier Ltd.

Keywords

Apatite
Crystal chemistry
Phase equilibira
Silicates
Yttria

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title = "Phase equilibria and crystal chemistry in the calcia-silica-yttria system",

abstract = "The phase equilibria in the CaO-SiO2-Y2O3 system have been assessed at 1400 °C and 1600 °C using powders prepared by precipitation from precursors. Four ternary phases were identified: Ca/Y-cyclosilicate (Ca3Y2Si6O26), silico-carnotite (Ca3Y2Si3O12), cuspidine (nominally Ca2Y2Si2O9), and apatite (solid solution based on Ca2Y8Si6O26). The melting temperature of each ternary phase was measured and the shape of the liquid field at 1600 °C was assessed. The study emphasizes understanding the extent and crystallographic origin of the solid solution homogeneity range for apatite between Ca0.5Y9(SiO4)6O2 and Ca2.5Y7.5(SiO4)6O1.75, deviations from the nominal cuspidine stoichiometry, and solubility of Y2O3 in the high-temperature α-Ca2SiO4 polymorph. The results are discussed in the context of molten silicate (CMAS) degradation of thermal and environmental barrier coatings (T/EBCs).",

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AU - Fabrichnaya, Olga

AU - Levi, Carlos G.

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AB - The phase equilibria in the CaO-SiO2-Y2O3 system have been assessed at 1400 °C and 1600 °C using powders prepared by precipitation from precursors. Four ternary phases were identified: Ca/Y-cyclosilicate (Ca3Y2Si6O26), silico-carnotite (Ca3Y2Si3O12), cuspidine (nominally Ca2Y2Si2O9), and apatite (solid solution based on Ca2Y8Si6O26). The melting temperature of each ternary phase was measured and the shape of the liquid field at 1600 °C was assessed. The study emphasizes understanding the extent and crystallographic origin of the solid solution homogeneity range for apatite between Ca0.5Y9(SiO4)6O2 and Ca2.5Y7.5(SiO4)6O1.75, deviations from the nominal cuspidine stoichiometry, and solubility of Y2O3 in the high-temperature α-Ca2SiO4 polymorph. The results are discussed in the context of molten silicate (CMAS) degradation of thermal and environmental barrier coatings (T/EBCs).

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Phase equilibria and crystal chemistry in the calcia-silica-yttria system

Abstract

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