Extending the single-crystal quartz pressure gauge up to hydrostatic pressure of 19 GPa

Abstract

In situ high‐pressure diffraction experiments on single‐crystal α‐quartz under quasi‐hydrostatic conditions up to 19 GPa were performed with diamond‐anvil cells. Isotropic pressures were calibrated through the ruby‐luminescence technique. A 4:1 methanol–ethanol mixture and the densified noble gases helium and neon were used as pressure media. The compression data revealed no significant influence of the pressure medium at room temperature on the high‐pressure behavior of α‐quartz. In order to describe its compressibility for use as a pressure standard, a fourth‐order Birch–Murnaghan equation of state (EoS) with parameters KT0 = 37.0 (3) GPa, KT0′ = 6.7 (2) and KT0′′ = −0.73 (8) GPa−1 was applied to fit the data set of 99 individual data points. The fit of the axial compressibilities yields MT0 = 104.5 (8) GPa, MT0′ = 13.7 (4), MT0′′ = −1.04 (11) GPa−1 (a axis) and MT0 = 141 (3) GPa, MT0′ = 21 (2), MT0′′ = 8.4 (6) GPa−1 (c axis), confirming the previously reported anisotropy. Assuming an estimated standard deviation of 0.0001% in the quartz volume, an uncertainty of 0.013 GPa can be expected using the new set of EoS parameters to determine the pressure.

Structural response of α-quartz under plate-impact shock compression

“…On the basis of peak fitting the intense (101) α-quartz peak, the density of the compressed α-quartz can be estimated to be ~3.65 g/cm 3 . This density is consistent with an extrapolation of the 300-K equation of state of α-quartz from static compression experiments ( 22 ), where the modest offset is consistent with the higher temperature along the Hugoniot ( Fig. 1 ).…”

“…For shock pressures from 39 to 65 GPa, quartz fully transforms to a new structure. The compressed α-quartz densities derived from fits to the XRD patterns in the mixed-phase region are consistent with an extrapolation of the 300-K equation of state of α-quartz from static compression experiments ( 22 ). The diffraction data from the transformed material are distinctly different from the stishovite pattern observed for shocked fused silica ( 19 ).…”

“…Black curves are guides to the eye. Blue open symbols are the 300-K static compression data for stishovite ( 35 ) and α-quartz ( 22 ). Blue dashed line is an extrapolated equation of state fit to the 300-K quartz data.…”

P21/c Postorthopyroxene γ-LiScGe2O6, a New Dense High-Pressure Polymorph and Its Direct Transformation from the Pbca Structure

“…Precise pressures, as required for the EoS determination, were obtained from the volume data of an extra quartz standard crystal (40 × 40 × 20 μm 3 ), applying the quartz gauge calibration data. 43 Thus, single-crystal X-ray diffraction (scXRD) used the 8-position centering technique. 44 The sample-crystal size was approximately 100 × 70 × 50 μm 3 .…”

Diamond-inclusion system recording old deep lithosphere conditions at Udachnaya (Siberia)

“…The diameter of the diamond culet was 600 μm. The sample was loaded together with a single crystal of quartz used as an internal pressure standard 57 . The unit-cell edge was measured on a four-circle STOE STADI IV diffractometer equipped with a point detector and controlled by the SINGLE software 58 and installed at the Department of Geosciences, University of Padova.…”