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4 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Ce2Si2O7 by Materials Project

Ce2Si2O7 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are two inequivalent Ce3+ sites. In the first Ce3+ site, Ce3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ce–O bond distances ranging from 2.29–2.70 Å. In the second Ce3+ site, Ce3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ce–O bond distances ranging from 2.43–2.80 Å. There are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.64–1.66 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.64–1.67 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 120 degrees geometry to two Si4+ atoms. In the second O2- site, O2- is bonded in a 1-coordinate geometry to three Ce3+ and one Si4+ atom. In the third O2- site, O2- is bonded in a 1-coordinate geometry to three Ce3+ and one Si4+ atom. In the fourth O2- site, O2- is bonded in a 1-coordinate geometry to two Ce3+ and one Si4+ atom. In the fifth O2- site, O2- is bonded in a 1-coordinate geometry to three Ce3+ and one Si4+ atom. In the sixth O2- site, O2- is bonded in a 1-coordinate geometry to two Ce3+ and one Si4+ atom. In the seventh O2- site, O2- is bonded in a 1-coordinate geometry to three Ce3+ and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ce2Si2O7 by Materials Project

Ce2Si2O7 crystallizes in the tetragonal P4_1 space group. The structure is three-dimensional. there are four inequivalent Ce3+ sites. In the first Ce3+ site, Ce3+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Ce–O bond distances ranging from 2.43–3.06 Å. In the second Ce3+ site, Ce3+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Ce–O bond distances ranging from 2.39–2.94 Å. In the third Ce3+ site, Ce3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ce–O bond distances ranging from 2.44–2.74 Å. In the fourth Ce3+ site, Ce3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ce–O bond distances ranging from 2.37–2.98 Å. There are four inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.61–1.68 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.62–1.67 Å. In the third Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.62–1.68 Å. In the fourth Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.62–1.68 Å. There are fourteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ce3+ and one Si4+ atom. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ce3+ and one Si4+ atom. In the third O2- site, O2- is bonded in a distorted single-bond geometry to three Ce3+ and one Si4+ atom. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to three Ce3+ and one Si4+ atom. In the fifth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ce3+ and two Si4+ atoms. In the sixth O2- site, O2- is bonded in a 2-coordinate geometry to two Ce3+ and one Si4+ atom. In the seventh O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to two Ce3+ and one Si4+ atom. In the eighth O2- site, O2- is bonded in a 1-coordinate geometry to two Ce3+ and one Si4+ atom. In the ninth O2- site, O2- is bonded in a 1-coordinate geometry to three Ce3+ and one Si4+ atom. In the tenth O2- site, O2- is bonded in a 2-coordinate geometry to one Ce3+ and two Si4+ atoms. In the eleventh O2- site, O2- is bonded in a 1-coordinate geometry to three Ce3+ and one Si4+ atom. In the twelfth O2- site, O2- is bonded in a 1-coordinate geometry to three Ce3+ and one Si4+ atom. In the thirteenth O2- site, O2- is bonded in a 1-coordinate geometry to three Ce3+ and one Si4+ atom. In the fourteenth O2- site, O2- is bonded in a 1-coordinate geometry to three Ce3+ and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Accelerated Design of Cost-Effective Thermal/Environmental Barrier Coatings based on High-Entropy Rare Earth Disilicates: A First-Principles Study

This project aims to design cost-effective thermal/environmental barrier coatings (TEBC) based on high entropy rare earth disilicates to protect SiC-based ceramic matrix composites from chemical and thermal attack for better performance of components in the hot section of gas turbine engines. To accelerate the alloy design, we utilize first-principles density functional theory (DFT) together with combinatorial chemistry methodology to predict key properties including phase stability, apparent bulk coefficient of thermal expansion (ABCTE), intrinsic lattice thermal conductivity, and temperature-dependent elastic constants. Specifically, this project focuses on β-RE2Si2O7 (RE=Yb, Y, Er, Lu, La, Ce,) with β-Yb2Si2O7 and β-Y2Si2O7 as the benchmark. Our DFT calculations predict that Er1/4Lu1/4Y3/4Yb3/4Si2O7 and Er1/2Lu1/2Y1/2Yb1/2Si2O7 have ultralow lattice thermal conductivity < 0.23 W/m/K at 1500 K and a good match of average ABCTE (5.1 - 5.2×10-6 K-1) with SiC. Owing to the low cost and abundant supply of Ce and La, the A- and G-La2Si2O7/Ce2Si2O7 disilicates are also studied. Our study shows that G-phase Ce2Si2O7 has an ultralow thermal conductivity (0.26 W/m/K at 1500 K) and the apparent bulk ABCTE (≈6.9×10-6 K-1) slightly higher than SiC, demonstrating great potential as low-cost high-performance T/EBC. However, La2Si2O7 and Ce2Si2O7 undergo an A-phase to G-phase polymorphic transition at around 1470 K.

environmental barrier coatings↗