Integrated experimental and computational methods for structure determination and characterization of a new, highly stable cesium silicotitanate phase, Cs{sub 2}TiSi{sub 6}O{sub 15} (SNL-A)
Exploratory hydrothermal synthesis in the system Cs{sub 2}O-SiO{sub 2}-TiO{sub 2}-H{sub 2}O has produced a new polymorph of Cs{sub 2}TiSi{sub 6}O{sub 15} (SNL-A) whose structure was determined using a combination of experimental and theoretical techniques ({sup 29}Si and {sup 133}Cs NMR, X-ray Rietveld refinement, and Density Functional Theory). SNL-A crystallizes in the monoclinic space-group Cc with unit cell parameters: a = 12.998(2) {angstrom}, b = 7.5014(3) {angstrom}, c = 15.156(3) {angstrom}, {eta} = 105.80(3) {degree}. The SNL-A framework consists of silicon tetrahedra and titanium octahedra which are linked in 3-, 5-, 6-, 7- and 8-membered rings in three dimensions. SNL-A is distinctive from a previously reported C2/c polymorph of Cs{sub 2}TiSi{sub 6}O{sub 15} by different ring geometries. Similarities and differences between the two structures are discussed. Other characterizations of SNL-A include TGA-DTA, Cs/Si/Ti elemental analyses, and SEM/EDS. Furthermore, the chemical and radiation durability of SNL-A was studied in interest of ceramic waste form applications. These studies show that SNL-A is durable in both radioactive and rigorous chemical environments. Finally, calculated cohesive energies of the two Cs{sub 2}TiSi{sub 6}O{sub 15} polymorphs suggest that the SNL-A phase (synthesized at 200 C) is energetically more favorable than the C2/c polymorph (synthesized at 1,050 C).
- Research Organization:
- Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 754332
- Report Number(s):
- SAND2000-1037J; 0000035211-000; 0000035211-000; TRN: US0002676
- Journal Information:
- Journal of Materials Chemistry, Other Information: Submitted to Journal of Materials Chemistry; PBD: 24 Apr 2000
- Country of Publication:
- United States
- Language:
- English
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