Structural changes of quartz-type crystalline and vitreous GeO2 under pressure.
Using a large volume high pressure apparatus, quartz-type crystalline GeO2 and Li2O-4GeO2 glass have been compressed up to 14 GPa at room temperature and their local structural changes have been investigated by an in-situ XAFS method. In quartz-type crystalline GeO2, the change of the coordination number from 4 to 6 begins above 8 GPa and finishes below 12 GPa. On decompression, reversal transition begins below 8 GPa and there is a large hysteresis. Almost no sixfold coordination of Ge is preserved after releasing pressure. Change of coordination number in vitreous Li2O-4GeO2 begins above 6 GPa and is completed below 10 GPa. Reversal transition begins below 10 GPa and the hysteresis is smaller than that of quartz-type GeO2. Change of coordination number in vitreous Li2O-4GeO2 is also reversal.
Ohtaka
O
O
Earth and Space Science, Osaka University, Toyonaka, Japan. ohtaka@ess.sci.osaka-u.ac.jp
Yoshiasa
A
A
Fukui
H
H
Murai
K I
KI
Okube
M
M
Katayama
Y
Y
Utsumi
W
W
Nishihata
Y
Y