Large-volume multianvil cells designed for chemical synthesis at high pressures

Two multianvil cell assemblies with octahedral edge lengths (OEL) of 18 and 25 mm have been developed, which allow sample volumes of up to 153 and 387 mm3, respectively. Pressure calibrations were performed at room temperature and 1200 °C using quenched samples, and at variable temperature using in situ synchrotron measurements. These calibrations employed 25.4 mm tungsten carbide anvils with a truncation edge length of 12 mm for the 18 mm OEL cell (18/12 configuration) and 15 mm for the 25 mm OEL cell (25/15 configuration) and yielded sample pressures of up to 10 and 7.5 GPa, respectively, at loads approaching 800 t. The measured thermal gradients at 1200 °C vary between 5–10 °C/mm (18/12) and 15–20 °C/mm (25/15). By combining large sample/reaction volumes with minimal thermal gradients, the new multianvil cell assemblies are especially useful for chemical synthesis at high-pressure, high-temperature conditions.