Displacements in the cationic motif of nonstoichiometric fluorite phases Ba{sub 1-x}R{sub x}F{sub 2+x} as a result of the formation of {l_brace}Ba{sub 8}[R{sub 6}F{sub 68-69}]{r_brace} clusters: II. The Ba{sub 1-x}R{sub x}F{sub 2+x} (R = Er, Yb, Lu; 0.1 < x < 0.3) crystals
- Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)
- Karpov Research Institute of Physical Chemistry (Obninsk Branch), State Scientific Center of the Russian Federation (Russian Federation)
The structure of single crystals of the nonstoichiometric phases Ba{sub 1-x}R{sub x}F{sub 2+x} (R = Er, Yb, Lu; 0.1 < x < 0.3) grown by the Bridgman method from the flux has been studied using X-ray diffraction and neutron diffraction analyses at a temperature of 293 K. The phases have a defect structure of the fluorite type and crystallize in the cubic system, space group of symmetry Fm3-barm. The displacements revealed in the cationic motif of the Ba{sub 1-x}R{sub x}F{sub 2+x} phases with R = Er, Yb, or Lu are interpreted as displacements of the Ba cations from the main structural positions upon the formation of {l_brace}Ba{sub 8}[R{sub 6}F{sub 68-69}]{r_brace} superclusters of structural defects. This interpretation of the experimental data agrees with the results obtained from the recent study of the Ba{sub 0.78}Tm{sub 0.22}F{sub 2.22} phase at room and low (110 K) temperatures and is confirmed by the coincidence of intercationic distances in the disordered phases Ba{sub 1-x}R{sub x}F{sub 2+x} and the ordered phases Ba{sub 4}R{sub 3}F{sub 17} (R = Y, Er, Yb). In addition to the well-known changes in the anionic motif, the revealed displacements in the cationic motif are good arguments for the supercluster structural model of the nonstoichiometric phases Ba{sub 1-x}R{sub x}F{sub 2+x}.
- OSTI ID:
- 22050837
- Journal Information:
- Crystallography Reports, Vol. 54, Issue 3; Other Information: Copyright (c) 2009 Pleiades Publishing, Ltd.; Country of input: International Atomic Energy Agency (IAEA); ISSN 1063-7745
- Country of Publication:
- United States
- Language:
- English
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