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Theoretical and Experimental Analysis of Structural Phase Transitions for ScF[SeO 3 ] and YF[SeO 3 ]
Author(s) -
Chou ShengChun,
Greiner Stefan,
Magdysyuk Oxana V.,
Dinnebier Robert E.,
Schleid Thomas
Publication year - 2014
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.201400287
Subject(s) - phase transition , materials science , corundum , crystallography , phase (matter) , diffraction , bar (unit) , x ray crystallography , analytical chemistry (journal) , chemistry , thermodynamics , organic chemistry , metallurgy , physics , meteorology , optics
Phase‐pure ScF[SeO 3 ] and YF[SeO 3 ] were synthesized via solid‐state reactions of the corresponding rare‐earth metal sesquioxides and trifluorides with selenium dioxide in excess of fluxing cesium bromide at 700 °C for 7 d. To avoid the formation of oxosilicates, these reactions took place in corundum crucibles embedded inside of evacuated fused silica ampoules. Upon cooling down below 13 °C, a pseudo ‐second‐order phase transition ( P 2 1 / m → P $\bar{1}$ or P 1) for ScF[SeO 3 ] occurs, which is similar to the high‐temperature phase transition of LuF[SeO 3 ]. By heating YF[SeO 3 ] above 319 °C, it undergoes a first‐order phase transition ( P 2 1 / c → P 2 1 / m ) without passing the intermediate P $\bar{1}$ modification in contrast to LuF[SeO 3 ]. Both the high‐temperature phase transition of YF[SeO 3 ] and the low‐temperature phase transition of ScF[SeO 3 ] were characterized by in‐situ X‐ray powder diffraction, X‐ray single‐crystal diffraction, thermal analysis DSC, and distortion‐mode analysis. For both cases the driving forces for the symmetry‐breaking phase transitions from the high‐ to the low‐temperature phases are discussed.