Development of two-stage multi-anvil apparatus for low-temperature measurements

Abstract

The two-stage 6-8 multi-anvil (MA8) apparatus is an important large-volume, high-pressure technique that has been widely used in the high pressure mineralogy and material synthesis, mainly at room temperature or above. Recently, we have successfully developed a two-stage MA8 apparatus for low-temperature physical property measurements. The first-stage anvils at top and bottom sides are fabricated as a single piece in order to reduce the total size of the cylindrical module, which is put in a top-loading high pressure cryostat and compressed by a 1000 ton hydraulic press. A castable, split octahedral gasket with integrated fin was specifically designed in order to introduce the electrical leads from the inside sample container filled with a liquid pressure transmitting medium. By using tungsten carbide (WC) second-stage cubes with a truncated edge length of 3 mm and an octahedral gasket with an edge length of 6 mm, we have successfully generated pressure over 20 GPa at room temperature. Since the high pressure limit can be pushed to nearly 100 GPa by using the sintered diamond second-stage cubes, our MA8 apparatus has a great potential to expand the current pressure capacity for precise low-temperature measurements with a large sample volume.
 Edited by: A. Goñi, A. Cantarero, J. S. Reparaz

Temperature-Pressure Phase Diagram and Possible Pressure-Driven New Electronic Phase in the Polar Metal LiOsO3

“…To this end, we are motived to follow T s of LiOsO 3 to much higher pressures than 6.5 GPa by employing a recently developed two-stage multianvil (MA8) apparatus for low-temperature measurements. 30 In complementary to previous studies, we find that T s (P) starts to deviate from the linear behavior and exhibits a strong bend over above 10 GPa. Unexpectedly, we discover a new pressuredriven electronic phase transition at P c ≈ 16.8(1) GPa, above which the resistance R(T) of LiOsO 3 at 18.5 GPa in the polar phase exhibit a distinct temperature profile in comparison with those at lower pressures.…”

“…More detailed information about the low-temperature MA8 apparatus and the pressure calibrations can be found in our previous publication. 30 Since the cooling of sample in the MA8 module is achieved by directly filling the cryostat with liquid nitrogen and then helium, it is difficult to control the cooling rate. In addition, the pushing columns driving on the MA8 module experience a strong contraction upon cooling down, which is compensated by the frequent movements of the hydraulic press in order to maintain a constant loading force on the MA8 module.…”