Phase transitions under high pressure
Clamped-piston cells are used to study matter under extreme pressure conditions by means of both macro- and microscopic investigations. This allows us to access quantum phase transitions, which occur close to the absolute zero temperature, when parameters such as magnetic field, chemical composition, or pressure are changed. Organic systems, characterized by weak bonds, are well-known to show phase transitions already at ~0.5 GPa.
The investigation of materials under extreme pressure conditions requires high-performance cells whose design invariably involves trade-offs between the maximum achievable pressure, the allowed sample volume, and the possibility of real-time pressure monitoring. With a newly conceived hybrid piston-clamped anvil cell, we offer a relatively simple and versatile system, suitable for nuclear magnetic resonance experiments up to 4.4 GPa. Finite-element models, taking into account mechanical and thermal conditions, were used to optimize and validate the design prior to the realization of the device. Cell body and gaskets were made of beryllium-copper alloy and the pistons and pusher were made of tungsten carbide, while the anvils consist of zirconium dioxide. The low-temperature pressure cell performance was tested by monitoring in situ the pressure-dependent 63Cu nuclear-quadrupole-resonance signal of Cu2O.
Our most recent publication on the topic:
N. Barbero, G. Abbiati, E. Enrico, G. Amato, E. Vittone, H.-R. Ott, J. Mesot, and T. Shiroka, "external pageDesign optimization through thermomechanical finite-element analysis of a hybrid piston-clamped anvil cell for nuclear magnetic resonance experiments", Rev. Sci. Instrum. 90, 013901 (2019).