INFRARED SPECTROSCOPIC STUDIES OF EXPERIMENTALLY SHOCK‐LOADED QUARTZ

Abstract

The infrared behavior of experimentally shock‐loaded quartz was studied in the wavenumber region 1400 to 100 cm −1 . In agreement with results of X‐ray investigations reported in an earlier paper, the infrared studies indicate that solid‐state (diaplectic or thetomorphic) SiO 2 ‐glass is formed upon release from shock pressures of about > 14.0 GPa; complete transformation occurs upon release from about 30.0 GPa. The structure of the solid‐state glass must be quite different from that of fused SiO 2 . While fused silica is supposed to consist of small “crystallites,” or of a network of SiO 4 ‐tetrahedra groups of tridymite‐like short‐range order, the positions of the infrared absorption bands of the shock‐produced solid‐state quartz glass lie practically at the same wave numbers as crystalline quartz. We conclude that diaplectic quartz glass consists structurally of extremely small quartz‐like “crystallites.” These crystallites are mutually linked in a disordered but structurally more open manner as in α‐quartz. The formation of short‐range ordered quartz‐type solid‐state SiO 2 glass is explained by the decomposition of a sixfold coordinated stishovite‐like high pressure phase upon pressure release at the relatively low shock temperatures (≤ 300°C at 30.0 GPa). The extremely short duration of the shock process may prevent the growth of the “quartz nuclei” to long‐range ordered crystallites.