Uniaxial Stress Component in WC Toroidal Anvils under High Pressure and Temperature

The uniaxial stress components (USC), t, have been measured in NaCl samples, under variable pressure and temperature, in tungsten carbide (WC) toroidal anvils by energy dispersive X-ray diffraction under synchrotron radiation in a large volume Paris-Edinburgh cell. It was observed that t increases with load and at p= 4.6 GPa, t = —0.6 GPa (measured from the mean value of the lattice parameter of NaCl). When heating is applied (under load), t decreases, and becomes zero for T < 600 K. On cooling at constant load, t remains negligible (t = 0.01 GPa) down to room temperature. After loading again (p = 3.8 GPa) at room temperature, t remains small (t = —0.07 GPa). A measurement of the FWHM of the diffraction peaks verifies the improvement in hydrostaticity after heating.