Phase changes and amorphization of zeolites at high pressures; the case of scolecite and mesolite

Abstract

Pressure-induced amorphous-phase transitions (amorphization) have been observed in framework silicates like quartz and feldspars. A similar crystalline to highly disordered solid phase transition is reported in this study for two zeolites, scolecite and mesolite. Pressure-induced amorphization is demonstrated using in situ X-ray diffraction and Raman spectroscopy. Before complete amorphization, progressive structural changes are observed below 10 GPa. The transition from the crystal to the amorphous phase is irreversible, and the pressure-quenched samples exhibit Raman spectra that bear strong resemblance to aluminosilicate glasses obtained by quenching a liquid. In some cases, however, decompression from 15 GPa of fully amorphized samples is accompanied by a rim recrystallization of the sample and preservation of an amorphous phase with a structure different from that quenched in other experiments. Shear stresses seem to have important control of the transformation occurring during the decompression of the samples.