A pressure calibration method for a portable wide-access “panoramic” cell

A simple and convenient pressure calibration method is developed for a newly designed portable wide-access ＇panoramic＇ cell. This cell is adapted to angle-dispersive-mode high-pressure in situ neutron diffraction of reactor neutron sources. This pressure calibration method has established a relationship between the cell pressure and the anvil displace- ment （gasket compression） based on the fixed-point calibration technique. By employing TiZr gasket with a thickness of 3 mm and WC anvil with a culet of 4 mm diameter, the average anvil displacements are 1.31 mm and 2.22 mm for Bi phase transitions （2.55 GPa and 7.7 GPa）, and 1.85 mm for Ba phase transitions （5.5 GPa）, respectively. In this pressure range, the pressure increases quickly with decreasing gasket thickness, and undergoes a linear increase with the anvil displacement. By extrapolating the calibration curve, the cell pressure will achieve 10 GPa when the anvil displacement is around 2.5 ram.

Pressure calibration and sound velocity measurement to 12 GPa in multi-anvil apparatus

We performed the pressure calibration to 12 GPa for 14/6 type(octahedron edge length/WC truncated edge length,in mm) cell assembly in DS 6 × 1400 multi-anvil apparatus by using the phase transitions in Bi(Ⅰ-Ⅱ2.55 GPa,Ⅲ-Ⅴ 7.67 GPa) and ZnTe(LPP-HPP Ⅰ 9.6 GPa,HPP Ⅰ-Ⅱ 12.0 GPa).As verification and application,sound velocity measurements on poly crystalline Al_(2)O_(3) to 12 GPa at room temperature were conducted and the ultrasonic result is in good agreement with previous reports.It demonstrates the feasibility of performing sound velocity measurements close to the mantle transition zone pressure condition in our laboratory.

In-situ ultrasonic calibrations of pressure and temperature in a hinge-type double-stage cubic large volume press

Here,simultaneous in-situ calibration of pressures and temperatures was performed in a hinge-type second-stage cubic large volume press(LVP)up to 15 GPa and 1400 K by an acoustic travel-time approach.Based on the recently reported P-tSand P-T-tP-tSequations for Al2O3buffer rod,the cell pressures and temperatures in the chamber of LVP were insitu determined,in comparison with those by conventional off-line(or fixed-points)pressure calibration method and direct thermocouple measurement,respectively.It is found that the cell pressures of the LVP chamber are significantly reduced after annealing at simultaneous high pressures and high temperatures,owing to the stress relaxation as accumulate in the LVP chamber.This acoustic travel-time method is verified to be a good way for precise determination of thermal(cell)pressures at high temperature conditions,and is of great importance and necessity to conduct in-situ physical property measurements under extreme high P-T conditions,especially when the precious synchrotron x-ray/neutron diffraction beams are not available.

Raman scattering from highly-stressed anvil diamond

The high-frequency edge of the first-order Raman mode of diamond reflects the stress state at the culet of anvil, and is often used for the pressure calibration in diamond anvil cell(DAC) experiments. Here we point out that the high-frequency edge of the diamond Raman phonon corresponds to the Brillouin zone(BZ) center Γ point as a function of pressure. The diamond Raman pressure gauge relies on the stability of crystal lattice of diamond under high stress. Upon the diamond anvil occurs failure under the uniaxial stress(197 GPa), the loss of intensity of the first-order Raman phonon and a stressdependent broad Raman band centered at 600 cm^(-1) are observed, which is associated with a strain-induced local mode corresponding to the BZ edge phonon of the L1 transverse acoustic phonon branch.