In situ Raman measurements of z-cut $\upalpha$-quartz shocked to 10 GPa

Abstract

The Raman spectrum of $\upalpha$-quartz under the z-axis shock compression was measured online by use of the High-Spectral-Resolution Laser Raman system. For the first time, three characteristic Raman peaks $(128\,\hbox {cm}^{{-1}},206\,\hbox {cm}^{{-1}},464\,\hbox {cm}^{{-1}})$ of $\upalpha$-quartz were simultaneously identified in single shock experiment. The pressure dependence of Raman shift corresponding to $\hbox {A}_{{1}}$ mode $(464\,\hbox {cm}^{{-1}})$ remained linear up to nearly 10GPa. The result shows that the sample was completely in the elastic deformation zone. It is found that the Raman shifts of $\hbox {A}_{{1}}$ modes $(206\,\hbox {cm}^{{-1}},464\,\hbox {cm}^{{-1}})$ which were correlated with that the bending and torsion of Si–O–Si bond angle under shock were different from that of hydrostatics at the same pressure or even the same volume compression ratio. The FWHM of $206\,\hbox {cm}^{{-1}}$ decreased with the increase of pressure, which was lower than that of hydrostatic pressure. It was shown that the decoupling of strong non-harmonic interaction between A mode phonons and two-acoustic phonons was suppressed by the increase of temperature. Especially, the Raman peak and the FWHM of mode E $(128\,\hbox {cm}^{{-1}})$ was almost identical with that before shock. The above experimental data show that, on the molecular vibration level, there are obvious differences between the compression mechanism of $\upalpha$-quartz under shock loading and hydrostatic These experimental data could be more detaily reflected in the compression mechanism of quartz under shock loading at the molecular motion level, and it was pointed out that the mechanism was distinctly different from that under hydrostatic.

Graphic abstract

In this paper, the Raman spectrum of $\upalpha$-quartz under the z-axis shock compression was measured online and compared with the frequency shift of Raman characteristic peaks ($128\,\hbox {cm}^{{-1}},206\,\hbox {cm}^{{-1}},464\,\hbox {cm}^{{-1}})$ under hydrostatic pressure. We briefly analyzed the compression mechanism of $\upalpha$-quartz at the molecular vibration level.