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Phase Transition and Lattice Thermal Expansion of Cs‐Deficient Pollucite, Cs 1− x Al 1− x Si 2+ x O 6 ( x ≤0.25), Compounds
Author(s) -
Kobayashi Hidehiko,
Sumino Saiko,
Tamai Sachiko,
Yanase Ikuo
Publication year - 2006
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2006.01188.x
Subject(s) - thermal expansion , x ray crystallography , lattice constant , crystallography , materials science , atmospheric temperature range , phase transition , analytical chemistry (journal) , lattice (music) , crystal structure , solid solution , diffraction , chemistry , metallurgy , condensed matter physics , physics , thermodynamics , chromatography , acoustics , optics
Cs‐deficient pollucite compounds with the general composition Cs 1− x Al 1− x Si 2+ x O 6 and a cubic pollucite structure at room temperature (RT) were prepared by a multistep solid‐state reaction. The single phase of the products was confirmed by powder X‐ray diffraction (XRD) analysis at RT. Structural phase transition was influenced by the Cs content of compounds of the Cs 1− x Al 1− x Si 2+ x O 6 series. Cs 0.8 Al 0.8 Si 2.2 O 6 and Cs 0.75 Al 0.75 Si 2.25 O 6 were cubic at 123 K from the XRD patterns and did not undergo structural phase transition. The lattice thermal expansion behavior of the Cs‐deficient pollucite compounds was investigated by low‐temperature and high‐temperature XRD analyses in the temperature range of 123–1173 K and was found to show a gradual decrease with decreasing Cs content of Cs 1− x Al 1− x Si 2+ x O 6 series. The variation in unit cell volume with temperature for each composition showed that Cs 0.8 Al 0.8 Si 2.2 O 6 and Cs 0.75 Al 0.75 Si 2.25 O 6 had significantly smaller degrees of lattice thermal expansion than CsAlSi 2 O 6 and Cs 0.9 Al 0.9 Si 2.1 O 6 . CsAlSi 2 O 6 , Cs 0.9 Al 0.9 Si 2.1 O 6 , Cs 0.8 Al 0.8 Si 2.2 O 6 , and Cs 0.75 Al 0.75 Si 2.25 O 6 showed linear coefficients of thermal expansion of 2.7 × 10 −6 , 2.2 × 10 −6 , 1.5 × 10 −6 , and 1.1 × 10 −6 K −1 , respectively, which are attributed to not only an increase in space ratio but also a decrease in Al/Si ratio in the framework in the unit cell.