期刊
ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE
卷 640, 期 15, 页码 3203-3211出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/zaac.201400287
关键词
Scandium; Yttrium; Fluoride oxoselenates; X-ray diffraction; Differential scanning calorimetry; Distortion-mode analysis
资金
- Deutscher Akademischer Austausch-Dienst (DAAD, Bonn, Germany)
- State of Baden-Wurttemberg (Stuttgart, Germany)
Phase-pure ScF[SeO3] and YF[SeO3] 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 degrees 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 degrees C, a pseudo-second-order phase transition (P2(1)/m -> P (1) over bar or P1) for ScF[SeO3] occurs, which is similar to the high-temperature phase transition of LuF[SeO3]. By heating YF[SeO3] above 319 degrees C, it undergoes a first-order phase transition (P2(1)/c -> P2(1)/m) without passing the intermediate P (1) over bar modification in contrast to LuF[SeO3]. Both the high-temperature phase transition of YF[SeO3] and the low-temperature phase transition of ScF[SeO3] 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.
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