Tailoring thermal properties of multi-component rare earth monosilicates

Mackenzie Ridley; John Gaskins; Patrick Hopkins; Elizabeth Opila

doi:10.1016/j.actamat.2020.06.012

Tailoring thermal properties of multi-component rare earth monosilicates

Mackenzie Ridley, John Gaskins, Patrick Hopkins, Elizabeth Opila

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

93 Scopus citations

Abstract

This work explores the possibility of tailoring the thermal conductivity and thermal expansion of rare earth monosilicates through the introduction of multiple rare earth cations in solid solution. Six rare earth monosilicates are studied: Sc₂SiO₅, Y₂SiO₅, Nd₂SiO₅, Dy₂SiO₅, Er₂SiO₅, and Yb₂SiO₅. Four equimolar binary cation mixtures and a five-cation equimolar mixture were characterized. Thermal expansion was measured up to 1200 °C with X-Ray Diffraction (XRD) and bulk thermal conductivity was measured by Hot Disk technique. The linear coefficient of thermal expansion (CTE) of mixed-cation systems followed a rule of mixtures, with average linear CTEs between 6 - 9 × 10⁻⁶ /°C. Scandium monosilicate showed a lower linear CTE value as well as a notably lower degree of CTE anisotropy than other rare earth monosilicates. Thermal conductivity was found to decrease below rule of mixtures values through increasing heterogeneity in rare earth cation mass and ionic radii, as expected for the thermal conductivity of solid-solutions. The five-cation equimolar RE₂SiO₅ (RE=Sc, Y, Dy, Er, and Yb) shows a thermal conductivity of 1.06 W/mK at room temperature, demonstrating that multi-component rare earth silicates are strong candidates for novel dual-purpose thermal and environmental barrier coatings.

Original language	English
Pages (from-to)	698-707
Number of pages	10
Journal	Acta Materialia
Volume	195
DOIs	https://doi.org/10.1016/j.actamat.2020.06.012
State	Published - Aug 15 2020
Externally published	Yes

Funding

This work was supported by program manager Adam Chamberlain and Rolls-Royce Inc. task order # 17-UVA-26, “Entropy Stabilized Silicate Investigation,” PI Elizabeth Opila, task order # 18-UVA-26, “Characterization of Thermal Properties and Chemical Stability of High Entropy Rare Earth Monosilicates,” co-PIs Patrick Hopkins/Elizabeth Opila, and the University of Virginia SEAS 2017-2018 Research Innovation Award, “Center for Exploring and Tailoring Thermal Conductivity of Defective Oxides” PI Elizabeth Opila, co-PIs Keivan Esfarjani, Patrick Hopkins, Jon Ihlefeld, Haydn Wadley. This work was partially supported by the National Science Foundation , Grant Number CBET-1706388 . Thanks to Dr. Bryan Harder (NASA Glenn Research Center) for supplying RE 2 SiO 5 powders and Dr. Helge Heinrich (University of Virginia) for TEM. This work was supported by program manager Adam Chamberlain and Rolls-Royce Inc. task order # 17-UVA-26, ?Entropy Stabilized Silicate Investigation,? PI Elizabeth Opila, task order # 18-UVA-26, ?Characterization of Thermal Properties and Chemical Stability of High Entropy Rare Earth Monosilicates,? co-PIs Patrick Hopkins/Elizabeth Opila, and the University of Virginia SEAS 2017-2018 Research Innovation Award, ?Center for Exploring and Tailoring Thermal Conductivity of Defective Oxides? PI Elizabeth Opila, co-PIs Keivan Esfarjani, Patrick Hopkins, Jon Ihlefeld, Haydn Wadley. This work was partially supported by the National Science Foundation, Grant Number CBET-1706388. Thanks to Dr. Bryan Harder (NASA Glenn Research Center) for supplying RE2SiO5 powders and Dr. Helge Heinrich (University of Virginia) for TEM.

Keywords

Environmental barrier coating
Rare earth silicates
Thermal conductivity
Thermal expansion

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10.1016/j.actamat.2020.06.012

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title = "Tailoring thermal properties of multi-component rare earth monosilicates",

abstract = "This work explores the possibility of tailoring the thermal conductivity and thermal expansion of rare earth monosilicates through the introduction of multiple rare earth cations in solid solution. Six rare earth monosilicates are studied: Sc2SiO5, Y2SiO5, Nd2SiO5, Dy2SiO5, Er2SiO5, and Yb2SiO5. Four equimolar binary cation mixtures and a five-cation equimolar mixture were characterized. Thermal expansion was measured up to 1200 °C with X-Ray Diffraction (XRD) and bulk thermal conductivity was measured by Hot Disk technique. The linear coefficient of thermal expansion (CTE) of mixed-cation systems followed a rule of mixtures, with average linear CTEs between 6 - 9 × 10−6 /°C. Scandium monosilicate showed a lower linear CTE value as well as a notably lower degree of CTE anisotropy than other rare earth monosilicates. Thermal conductivity was found to decrease below rule of mixtures values through increasing heterogeneity in rare earth cation mass and ionic radii, as expected for the thermal conductivity of solid-solutions. The five-cation equimolar RE2SiO5 (RE=Sc, Y, Dy, Er, and Yb) shows a thermal conductivity of 1.06 W/mK at room temperature, demonstrating that multi-component rare earth silicates are strong candidates for novel dual-purpose thermal and environmental barrier coatings.",

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author = "Mackenzie Ridley and John Gaskins and Patrick Hopkins and Elizabeth Opila",

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AU - Gaskins, John

AU - Hopkins, Patrick

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N2 - This work explores the possibility of tailoring the thermal conductivity and thermal expansion of rare earth monosilicates through the introduction of multiple rare earth cations in solid solution. Six rare earth monosilicates are studied: Sc2SiO5, Y2SiO5, Nd2SiO5, Dy2SiO5, Er2SiO5, and Yb2SiO5. Four equimolar binary cation mixtures and a five-cation equimolar mixture were characterized. Thermal expansion was measured up to 1200 °C with X-Ray Diffraction (XRD) and bulk thermal conductivity was measured by Hot Disk technique. The linear coefficient of thermal expansion (CTE) of mixed-cation systems followed a rule of mixtures, with average linear CTEs between 6 - 9 × 10−6 /°C. Scandium monosilicate showed a lower linear CTE value as well as a notably lower degree of CTE anisotropy than other rare earth monosilicates. Thermal conductivity was found to decrease below rule of mixtures values through increasing heterogeneity in rare earth cation mass and ionic radii, as expected for the thermal conductivity of solid-solutions. The five-cation equimolar RE2SiO5 (RE=Sc, Y, Dy, Er, and Yb) shows a thermal conductivity of 1.06 W/mK at room temperature, demonstrating that multi-component rare earth silicates are strong candidates for novel dual-purpose thermal and environmental barrier coatings.

AB - This work explores the possibility of tailoring the thermal conductivity and thermal expansion of rare earth monosilicates through the introduction of multiple rare earth cations in solid solution. Six rare earth monosilicates are studied: Sc2SiO5, Y2SiO5, Nd2SiO5, Dy2SiO5, Er2SiO5, and Yb2SiO5. Four equimolar binary cation mixtures and a five-cation equimolar mixture were characterized. Thermal expansion was measured up to 1200 °C with X-Ray Diffraction (XRD) and bulk thermal conductivity was measured by Hot Disk technique. The linear coefficient of thermal expansion (CTE) of mixed-cation systems followed a rule of mixtures, with average linear CTEs between 6 - 9 × 10−6 /°C. Scandium monosilicate showed a lower linear CTE value as well as a notably lower degree of CTE anisotropy than other rare earth monosilicates. Thermal conductivity was found to decrease below rule of mixtures values through increasing heterogeneity in rare earth cation mass and ionic radii, as expected for the thermal conductivity of solid-solutions. The five-cation equimolar RE2SiO5 (RE=Sc, Y, Dy, Er, and Yb) shows a thermal conductivity of 1.06 W/mK at room temperature, demonstrating that multi-component rare earth silicates are strong candidates for novel dual-purpose thermal and environmental barrier coatings.

KW - Environmental barrier coating

KW - Rare earth silicates

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KW - Thermal expansion

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Tailoring thermal properties of multi-component rare earth monosilicates

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