High-pressure generation above 45 GPa over a 10 mm3 volume with a multi-anvil press.

High-pressure generation in multi-anvil presses has long been limited to pressures below ∼25 GPa when millimeter-scale samples are required. In this study, we systematically optimized the experimental setup for a Kawai-cell assembly using tungsten carbide anvils with a truncation edge length (TEL) of 3 mm to extend the achievable pressure range. Our results show that, in contrast to previous studies using smaller assemblies (TEL = 1.5 and 1.0 mm), tapering the anvils solely has a negligible effect on pressure-generation capability for the large sample volumes investigated here, despite a substantial increase in anvil gap under the same load. In contrast, reducing the gasket volume significantly improves the efficiency of press-load transmission to the sample, enabling an ∼33% increase in pressure compared with conventional designs using the same type of anvil. Using the optimized gasket design together with ultrahard tungsten carbide anvils with a 1° taper (TJS01, Fujilloy; TEL = 3 mm), pressures of up to 45.8 GPa were achieved at room temperature while maintaining a truncation-confined volume >10 mm3 and an anvil gap >0.3 mm. This technical breakthrough not only enables the synthesis of functional materials with large sample volumes at pressures above 45 GPa but also opens doors to unprecedentedly high pressures for precise physical property measurements that require large sample volumes and large anvil gaps, including ultrasonic interferometry, electrical impedance, and thermal conductivity measurements in a multi-anvil press.