STRUCTURAL-CHANGE OF GEO2 UNDER PRESSURE

Pressure-induced amorphization of alpha-quartz type GeO2 was studied w ith a newly developed X-ray diffraction system which consists of a 4-c ircle goniometer and a curved position sensitive detector. Single-crys tal diffraction was measured under pressurs up to 7.3 GPa at room temp erature in order to investigate pretransitional phenomena. Diffraction intensity and line width of the diffraction profiles showed no remark able change up to 5.9 GPa. However, no sharp diffraction line was obse rved at pressures over 6.5 GPa. The bulk modulus at 0.1 MPa and its pr essure derivative of alpha-quartz type GeO2 were determined to be K(T) = 32.8(3.3) GPa and K(T) = 6.0(2.0), respectively. In situ microscopi c observations of the amorphization transformation was also performed. The large volume change due to amorphization was observed and estimat ed to be about 10%.