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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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7 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Understanding the Instability of the Halide Perovskite CsPbI 3 through Temperature-Dependent Structural Analysis

Despite the tremendous interest in halide perovskite solar cells, the structural reasons that cause the all-inorganic perovskite CsPbI 3 to be unstable at room temperature remain mysterious, especially since many tolerance-factor-based approaches predict CsPbI 3 should be stable as a perovskite. Here single-crystal X-ray diffraction and X-ray pair distribution function (PDF) measurements characterize bulk perovskite CsPbI3 from 100 to 295 K to elucidate its thermodynamic instability. While Cs occupies a single site from 100 to 150 K, it splits between two sites from 175 to 295 K with the second site having a lower effective coordination number, which, along with other structural parameters, suggests that Cs rattles in its coordination polyhedron. PDF measurements reveal that on the length scale of the unit cell, the Pb-I octahedra concurrently become greatly distorted, with one of the I-Pb-I angles approaching 82° compared to the ideal 90°. The rattling of Cs, low number of Cs-I contacts, and high degree of octahedral distortion cause the instability of perovskite-phase CsPbI 3 . These results reveal the limitations of tolerance factors in predicting perovskite stability and provide detailed structural information that suggests methods to engineer stable CsPbI 3 -based solar cells.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Cs 3 Bi 2 I 9 -hydroxyapatite composite waste forms for cesium and iodine immobilization

Perovskite-based ceramic composites were developed as potential waste form materials for immobilizing cesium (Cs) and iodine (I) with high waste loadings and chemical durability. The perovskite Cs 3 Bi 2 I 9 has high Cs (22 wt%) and I (58 wt%) content, and thus can be used as a potential host phase to immobilize these critical radionuclides. In this work, the perovskite Cs 3 Bi 2 I 9 phase was synthesized by a cost effective solution-based approach, and was embedded into a highly durable hydroxyapatite matrix by spark plasma sintering to form dense ceramic composite waste forms. The chemical durabilities of the monolithic Cs 3 Bi 2 I 9 and Cs 3 Bi 2 I 9 -hydroxyapatite composite pellets were investigated by static and semi-dynamic leaching tests, respectively. Cs and I are incongruently released from the matrix for both pure Cs 3 Bi 2 I 9 and composite structures. The normalized Cs release rate is faster than that of I, which can be explained by the difference in the strengths between Cs-I and Bi-I bonds as well as the formation of insoluble micrometer-sized BiOI precipitates. The activation energies of elemental releases based on dissolution and diffusion-controlled mechanisms are determined with significantly higher energy barriers for dissolution from the composite versus that of the monolithic Cs 3 Bi 2 I 9 . The ceramic-based composite waste forms exhibit excellent chemical durabilities and waste loadings, commensurate with the state-of-the-art glass-bonded perovskite composites for I and Cs immobilization.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Materials Data on CsI3 by Materials Project

CsI3 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Cs is bonded in a 10-coordinate geometry to ten I atoms. There are a spread of Cs–I bond distances ranging from 3.95–4.55 Å. There are three inequivalent I sites. In the first I site, I is bonded in a distorted rectangular see-saw-like geometry to two equivalent Cs and two I atoms. There are one shorter (2.90 Å) and one longer (3.02 Å) I–I bond lengths. In the second I site, I is bonded in a 5-coordinate geometry to four equivalent Cs and one I atom. In the third I site, I is bonded in a 3-coordinate geometry to four equivalent Cs and one I atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CsI4 by Materials Project

CsI4 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Cs is bonded in a 9-coordinate geometry to ten I atoms. There are a spread of Cs–I bond distances ranging from 3.99–4.49 Å. There are four inequivalent I sites. In the first I site, I is bonded in a 5-coordinate geometry to three equivalent Cs and two I atoms. There are one shorter (2.85 Å) and one longer (3.34 Å) I–I bond lengths. In the second I site, I is bonded to three equivalent Cs and two I atoms to form a mixture of distorted edge and corner-sharing ICs3I2 trigonal bipyramids. The I–I bond length is 3.02 Å. In the third I site, I is bonded in a 3-coordinate geometry to one Cs and two I atoms. The I–I bond length is 2.90 Å. In the fourth I site, I is bonded in a 4-coordinate geometry to three equivalent Cs and one I atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CsI by Materials Project

CsI is Halite, Rock Salt structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Cs1+ is bonded to six equivalent I1- atoms to form a mixture of edge and corner-sharing CsI6 octahedra. The corner-sharing octahedral tilt angles are 0°. All Cs–I bond lengths are 3.93 Å. I1- is bonded to six equivalent Cs1+ atoms to form a mixture of edge and corner-sharing ICs6 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CsY by Materials Project

CsY is alpha Samarium-derived structured and crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Cs is bonded to six equivalent Cs and six equivalent Y atoms to form CsCs6Y6 cuboctahedra that share corners with eighteen equivalent CsCs6Y6 cuboctahedra, edges with six equivalent CsCs6Y6 cuboctahedra, edges with twelve equivalent YCs6Y6 cuboctahedra, faces with eight equivalent CsCs6Y6 cuboctahedra, and faces with twelve equivalent YCs6Y6 cuboctahedra. All Cs–Cs bond lengths are 3.84 Å. All Cs–Y bond lengths are 4.36 Å. Y is bonded to six equivalent Cs and six equivalent Y atoms to form YCs6Y6 cuboctahedra that share corners with eighteen equivalent YCs6Y6 cuboctahedra, edges with six equivalent YCs6Y6 cuboctahedra, edges with twelve equivalent CsCs6Y6 cuboctahedra, faces with eight equivalent YCs6Y6 cuboctahedra, and faces with twelve equivalent CsCs6Y6 cuboctahedra. All Y–Y bond lengths are 3.84 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CsI by Materials Project

CsI is Tetraauricupride structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Cs1+ is bonded in a body-centered cubic geometry to eight equivalent I1- atoms. All Cs–I bond lengths are 4.04 Å. I1- is bonded in a body-centered cubic geometry to eight equivalent Cs1+ atoms.

36 MATERIALS SCIENCE↗