Investigation of the hydrothermal crystallisation of the perovskite solid solution NaCe{sub 1−x}La{sub x}Ti{sub 2}O{sub 6} and its defect chemistry
- Department of Chemistry, University of Warwick, Coventry CV4 7AL (United Kingdom)
- Department of Physics, University of Warwick, Coventry CV4 7Al (United Kingdom)
- School of Chemistry, and EaStCHEM University of St. Andrews, North Haugh, St. Andrews, KY16 9ST (United Kingdom)
Perovskites of nominal composition NaCe{sub 1−x}La{sub x}Ti{sub 2}O{sub 6} (0≤x≤1) crystallise directly under hydrothermal conditions at 240 °C. Raman spectroscopy shows distortion from the ideal cubic structure and Rietveld analysis of powder X-ray and neutron diffraction reveals that the materials represent a continuous series in rhombohedral space group R3-bar c. Ce L{sub III}-edge X-ray absorption near edge structure spectroscopy shows that while the majority of cerium is present as Ce{sup 3+} there is evidence for Ce{sup 4+}. The paramagnetic Ce{sup 3+} affects the chemical shift and line width of {sup 23}Na MAS NMR spectra, which also show with no evidence for A-site ordering. {sup 2}H MAS NMR of samples prepared in D{sub 2}O shows the inclusion of deuterium, which IR spectroscopy shows is most likely to be as D{sub 2}O. The deuterium content is highest for the cerium-rich materials, consistent with oxidation of some cerium to Ce{sup 4+} to provide charge balance of A-site water. - Graphical abstract: A multi-element A-site perovskite crystallises directly from aqueous, basic solutions at 240 °C; while the paramagnetic effect of Ce{sup 3+} on the {sup 23}Na NMR shows a homogeneous solid-solution, the incorporation of A-site water is also found from {sup 2}H NMR and IR, with oxidation of some cerium to charge balance proved by XANES spectroscopy. Display Omitted - Highlights: • Direct hydrothermal synthesis allows crystallisation of a perovskite solid-solution. • XANES spectroscopy shows some oxidation of Ce{sup 3+} to Ce{sup 4+}. • The paramagnetism of Ce{sup 3+} shifts and broadens the {sup 23}Na solid-state NMR. • The perovskite materials incorporate water as an A-site defect.
- OSTI ID:
- 22274153
- Journal Information:
- Journal of Solid State Chemistry, Vol. 207; Other Information: Copyright (c) 2013 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ABSORPTION SPECTROSCOPY
CERIUM
CERIUM IONS
CRYSTALLIZATION
DEUTERIUM
HYDROTHERMAL SYNTHESIS
INFRARED SPECTRA
NEUTRON DIFFRACTION
NMR SPECTRA
NUCLEAR MAGNETIC RESONANCE
OXIDATION
PARAMAGNETISM
PEROVSKITE
RAMAN SPECTROSCOPY
SODIUM 23
SOLID SOLUTIONS
TRIGONAL LATTICES
X RADIATION
X-RAY DIFFRACTION
X-RAY SPECTROSCOPY