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Author Varadé-López, R. ♦ Ávila-Brande, D. ♦ Urones-Garrote, E. ♦ Otero-Díaz, L. C.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY ♦ COMPUTERIZED TOMOGRAPHY ♦ CRYSTAL STRUCTURE ♦ CRYSTALS ♦ MAGNESIUM SULFIDES ♦ MICROSTRUCTURE ♦ SLABS ♦ SODIUM CHLORIDES ♦ SOLID SOLUTIONS ♦ SPINELS ♦ STOICHIOMETRY ♦ THULIUM SULFIDES ♦ TRANSMISSION ELECTRON MICROSCOPY ♦ TWINNING ♦ VACANCIES
Abstract This work presents the structural–microstructural characterization of the NaCl-derivative MgS–Tm{sub 2}S{sub 3} system, which can be formulated by the expression Mg{sub (1−x)}Tm{sub (2/3)x}□{sub (1/3)x}S (□→cation vacancy). Transmission electron microscopy observations show the transition between NaCl-type and spinel-type structures when 0 ≤x≤ 0.75. The increase of Tm content in the solid solution provokes the increase of the spinel-type phase proportion, which intergrows with the NaCl-type crystals. When x≥0.75, some phases derived from NaCl-type structure through the chemical twinning at the unit cell level crystallographic operation are observed, such as CT-MgTm{sub 2}S{sub 4} and CT-MgTm{sub 4}S{sub 7}. The existence and nature of the extended defects observed along the c direction of these structures are characterized by means of Scanning-Transmission electron microscopy high-angle dark field imaging, which allows observing the presence of quasi ordered crystals with new possible complex stoichiometries at atomic resolution. - Graphical abstract: HAADF-STEM image of a disordered CT-MgYb{sub 2}S{sub 4} crystal. The disordered twin-slab sequences are marked by arrows. - Highlights: • Structural evolution of the Mg{sub (1−x)}Tm{sub (2/3)x}□{sub (1/3)x}S system was characterized by means of TEM. • The increase in Tm content provokes the transition from NaCl to spinel-type structure up to x=0.75. • Chemical twinned phases CT-MgTm{sub 2}S{sub 4} and CT-MgTm{sub 4}S{sub 7} are observed at high Tm contents. • Extended defects in CT-crystals are characterized with atomic resolution STEM-HAADF images.
ISSN 00224596
Educational Use Research
Learning Resource Type Article
Publisher Date 2015-09-15
Publisher Place United States
Journal Journal of Solid State Chemistry
Volume Number 229


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