Tailoring thermal properties of multi-component rare earth monosilicates. (15th August 2020)

• Record Type: Journal Article
• Authors: Ridley, Mackenzie; Gaskins, John; Hopkins, Patrick; Opila, Elizabeth
• Is Part Of: Acta materialia. Volume 195(2020)
• Page Start: 698
• Page End: 707
• Publication Date: 2020-08-15
• Subjects: Environmental barrier coating -- Thermal expansion -- Thermal conductivity -- Rare earth silicates; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2020.06.012
• Languages: English
• ISSNs: 1359-6454

Abstract

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: Sc2 SiO5, Y2 SiO5, Nd2 SiO5, Dy2 SiO5, Er2 SiO5, and Yb2 SiO5 . 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 RE2 SiO5 (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. Graphical abstract: Image, graphical abstract