1995 年 37 巻 5 号 p. 243-250
In the last decade the pressure-induced amorphization of several crystals such as SiO2, Ca (OH) 2, H2O, GeO2, α-AlPO4 etc. have been found under compression at room temperature. The pressure-induced amorphization was previously regarded as the thermodynamically metastable phase, which corresponds the super cooled liquid phase at room temperature. The amorphization is a precursor phenomenon of the phase transition to the high pressure form. There are two different types of the reversible and irreversible amorphization. Dynamical lattice-instability due to shear and stress induces the reversible amorphization, which produces memory glass. On the other hand the irreversible mode is attributed to the nucleation of highpressure form in the parent lattice but thermal energy is not high enough to provide the large crystallite size coherent to the X-ray wave length. The successive structure change of the pressure-induced amorphizaiton was investigated under various pressure and temperature by X-ray diffraction study, XAFS and Raman spectroscopy with diamond anvil pressure cell.