Crystal structures of orthorhombic, hexagonal, and cubic compounds of the Sm(x)Yb(2−x)TiO5 series

• Published in: Journal of solid state chemistry Vol. 213; pp. 182 - 192
• Main Authors: Aughterson, Robert D., Lumpkin, Gregory R., Reyes, Massey de los, Sharma, Neeraj, Ling, Christopher D., Gault, Baptiste, Smith, Katherine L., Avdeev, Maxim, Cairney, Julie M.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01-05-2014; Elsevier
• Subjects: Condensed matter: structure, mechanical and thermal properties; Crystalline state (including molecular motions in solids); Crystallographic aspects of phase transformations; pressure effects; Exact sciences and technology; Ln2TiO5; Neutron diffraction and scattering; Physics; Single-crystal and powder diffraction; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Synchrotron diffraction; TEM; Ln2TiO5; Synchrotron diffraction; TEM; Cubic lattices; Stoichiometry; Ln; Neutron diffraction; Modulated materials; Modulated structure; XRD; Hexagonal lattices; Monocrystals; Transmission electron microscopy; Rare earths; Orthorhombic lattices; Short-range order; TiO; Synchrotron radiation; Polymorphism; Crystal structure
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2014.02.029

A series of single phase compounds with nominal stoichiometry Sm(x)Yb(2−x)TiO5 (x=2, 1.4, 1, 0.6, and 0) have been successfully fabricated to generate a range of crystal structures covering the most common polymorphs previously discovered in the Ln2TiO5 series (Ln=lanthanides and yttrium). Four of the five samples have not been previously fabricated in bulk, single phase form so their crystal structures are refined and detailed using powder synchrotron and single crystal x-ray diffraction, neutron diffraction and transmission electron microscopy. Based on the phase information from diffraction data, there are four crystal structure types in this series; orthorhombic Pnma, hexagonal P63/mmc, cubic (pyrochlore-like) Fd-3m and cubic (fluorite-like) Fm-3m. The cubic materials show modulated structures with variation between long and short range ordering and the variety of diffraction techniques were used to describe these complex crystal structure types.
A high resolution image of the compound Sm0.6Yb1.4TiO5 showing contrast from lattice fringes and the corresponding fast Fourier transform (FFT) of the HREM image with pyrochlore related diffraction spots marked “P” and fluorite marked “F”. The crystal is oriented down the [110] zone axis based on the Fd-3m structure. The ideal crystal structure (no vacancies) of the cubic, pyrochlore-like (Sm0.6Yb1.4TiO5). [Display omitted]
•First fabrication of bulk single-phase material with stoichiometry Sm2TiO5.•Systematic study of crystal structure types within Ln2TiO5 series (Ln=lanthanides).•A novel technique using IFFT of HREM images to study cubic structures.