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Temperature-induced phase transitions for stuffed tridymites SrGa2O4 and CaGa2O4.
- Source :
-
Journal of Solid State Chemistry . Oct2017, Vol. 254, p195-199. 5p. - Publication Year :
- 2017
-
Abstract
- Temperature-induced phase transitions for stuffed tridymite A Ga 2 O 4 ( A = Sr, Ca) were investigated by experimental and theoretical calculations. A simple annealing of SrCO 3 and Ga 2 O 3 led to the formation of γ-SrGa 2 O 4 ( P 2 1 /n ) below 1200 °C, and transform to β-SrGa 2 O 4 ( P 2 1 /c ) when heated at 1200 °C. A similar phenomenon was found for CaGa 2 O 4 , and the temperature boundary between α-CaGa 2 O 4 ( Pna 2 1 ) and the high temperature polymorph β-CaGa 2 O 4 ( P 2 1 /c ) was about 1350 °C. Rietveld refinements provided detailed structural information for these polymorphs and suggest that the driving force of these phase transitions is the under-bonded nature of the alkaline earth cations. In other words, the need of larger space for Sr 2+ /Ca 2+ in the high temperature β-phase forces the 6-membered-ring channel expand through increasing the Ga-O-Ga angles. Density functional theory calculations proved the formation energies for γ-SrGa 2 O 4 and α-CaGa 2 O 4 were both lower than their high temperature β-polymorphs, in accordance with the experimental observations. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00224596
- Volume :
- 254
- Database :
- Academic Search Index
- Journal :
- Journal of Solid State Chemistry
- Publication Type :
- Academic Journal
- Accession number :
- 124578668
- Full Text :
- https://doi.org/10.1016/j.jssc.2017.07.024