Fig. 1. Ceramacast 646 pressure media for use in multianvil pressurizations. Dimensional abbreviations: TEL = truncated edge length of the triangular corner facet on a tungsten carbide anvil, which will mate to the pressure medium’s triangular octahedral face. GT = gasket thickness. EW = equatorial width. Regular octahedra of 10 mm and 8 mm EW without integral cast gaskets are for mating to 5 mm and 3 mm TEL anvils with COMPRES pyrophyllite gaskets.

Fig. 2. 8 mm TEL Bi calibrations at room temperature. Ceramacast 646 (red, purple, blue, and pink) are compared with 584 (green and orange).

Fig. 3. 12 mm TEL Bi calibrations at room temperature. Ceramacast 646 (orange) is compared to 584 (green and purple).

Fig. 4. 19 mm “finless” Bi calibrations at room temperature for Ceramacast 646.

Fig. 5. Summary of Bi calibrations at room temperature in Ceramacast 646.

Fig. 6. High-temperature load-and-quench calibrations for CaGeO₃ and SiO₂ in 646. Abbreviations: quartz (qtz), coesite (coes), garnet (grt), perovskite (pvsk).

Fig. 7. Raman spectra of starting materials and products of calibration experiments. The spectra were collected using a Renishaw Raman microscope, with 532 nm unpolarized laser light, a 50× objective (2 μm area) in the nonfocal mode, and an 1800 l/mm grating. The collection time ranged between 1 and 60 s. Results are shown without background subtraction.

Fig. 8. CaGeO₃ polymorphs wrapped in Pt display color differences: garnet is white, perovskite is tan/pink.

Fig. 9. High temperature calibrations using Mg₂SiO₄ starting materials for 3 mm and 5 mm TEL octahedra with pyrophyllite gaskets. Data are found in Table III. The results of experiments using COMPRES injection molded octahedra (black symbols) are in good agreement with the black curves reproduced from Leinenweber et al.³ The results of experiments using 646 cast octahedra (red symbols) are used to constrain the red dashed curves. Circles denote two phases coexisting. Left- and right-pointing wedges denote single phases at higher tonnage or lower tonnage, respectively, than the relevant phase boundary at the experimental temperature. In experiment M080319, ringwoodite was the product at 715 tons and 1500 °C. The two red-filled wedges indicate that the tonnage was above that required for the rw/wd transition at 20.3 GPa and below that required for the rw/bm + pc transition at 23.3 GPa. Thus, sample pressure is greater than the 20.3 GPa needed for the rw/wd boundary and less than the 23.3 GPa needed to achieve the rw/bm + pc boundary. Abbreviations: forsterite (fo), wadsleyite (wd), ringwoodite (rw), bridgmanite (bm), periclase (pc).

Fig. 10. Pressure calibrations of 8 mm TEL anvils based on the melting curve of NaCl. Black (584) and red (646) lines are linear fits to load-and-quench calibration experiments using SiO₂ and CaGeO₃ (Table III). Red circles and black squares represent pressures determined from the melting temperatures of NaCl (marked next to the 646 data points) at various press loads.

Fig. 11. Thermal structure in 8 mm 646 assembly with LaCrO₃ heater determined by two independent thermocouples 2 mm apart.

Fig. 12. Resistance of Bi as a function of press load for an 8 mm TEL octahedron with integral gaskets cast from 646 ceramic. Abrupt resistance changes correspond to phase changes between Bi polymorphs. Red dashed line is the initial linear slope of the Bi I–II transition. Yellow dashed trace, based on Bundy,¹⁴ is the theoretical trace if the transformations were instantaneous and without hysteresis. The real trace, BB-1200, taken over 17 h exhibits smearing of the Bi II stability to higher-than-equilibrium pressures.

Fig. 13. Shows the Bi calibrations of Fig. 5, except that Bi II–III, plotted as open symbols for the tonnage at the lowest point of the V valley, is plotted at 27 kbar instead of 31 kbar. It is clear that the open symbols fall systematically off and below the calibration curves shown here, which are based on fitting the standard values of Bi I–II = 25.5 kbar and Bi III–V = 77 kbar.

Table 1. Room temperature Bi calibration in cast octahedra with integral fin gaskets.

Table 2. High temperature SiO₂ and CaGeO₃ calibrations in cast octahedra with integral fin gaskets.^a

Table 3. High temperature Mg₂SiO₄ calibrations in finless octahedra with pyrophyllite gaskets.

Table 4. High temperature NaCl melting calibrations in octahedra with integral fin gaskets for 8 mm TEL WC anvils.^a