Zum Hauptinhalt springen

Research Highlights

On the nature of the phase transitions of aluminosilicate perrhenate sodalite

Kowsik Ghosh, M. Mangir Murshed, Thomas Frederichs, Naveen K. C. Muniraju, Thorsten M. Gesing

Zeitschrift für Kristallographie - Crystalline Materials (2020), 235, 6-7

https://doi.org/10.1515/zkri-2020-0027

The temperature-dependent structure-property relationships of the aluminosilicate perrhenate sodalite |Na8(ReO4)2|[AlSiO4]6 (ReO4-SOD) were analysed via powder X-ray diffraction (PXRD), Raman spectroscopy and heat capacity measurements. ReO4-SOD shows two phase transitions in the investigated temperature range (13 K < T < 1480 K). The first one at 218.6(1) K is correlated to the transition of dynamically ordered P¯43n (> 218.6(1 K) to a statically disordered (<218.6(1) K) SOD template in P¯43n. The loss of the dynamics of the template anion during cooling causes an increase of disorder, indicated by an unusual intensity decrease of the 011-reflection and an increase of the Re-O2 bond length with decreasing temperature. Additionally, Raman spectroscopy shows a distortion of the ReO4 anion. Upon heating the thermal expansion of the sodalite cage originated in the tilt-mechanism causes the second phase transition at 442(1) K resulting in a symmetry-increase from P¯43n to Pm¯3n, the structure with the sodalites full framework expansion. Noteworthy is the high decomposition temperature of 1320(10) K.

Aktualisiert von: MAPEX