Structural analysis of pressure-amorphized zirconium tungstate

Abstract

The negative thermal-expansion material zirconium tungstate, when subjected to a moderate pressure of 2 GPa, turns amorphous irreversibly; the amorphous state being ϳ26% more dense than the crystalline phase ␣-Zr͑WO 4 ͒ 2 . Structure of pressure-amorphized Zr͑WO 4 ͒ 2 is investigated using synchrotron x-ray diffraction. Structure factors S͑q͒ of samples recovered from different pressures are obtained. The first peak in S͑q͒ for 10.5 GPa-treated sample is found to occur at a slightly larger q than that recovered from 5.5 GPa, suggesting that the amorphous samples recovered from higher pressure could be more dense. The pair-correlation functions g͑r͒, obtained by Fourier transforming S͑q͒, suggests that the further densification of amorphous phase occurs via contraction of second and third neighbor shells representing O-O and W-W and W-Zr distances rather than first neighbor shell. In contrast to earlier speculations, the present results do not show evidence for an increase in the coordination number and consequent existence of distinct amorphous phases in samples recovered from pressures up to 10.5 GPa.

Zeeman spectroscopy of excitons and hybridization of electronic states in few-layer WSe 2 , MoSe 2 and MoTe 2

“…The emitted polarized light is collected using an optical fiber of 200 µm diameter, dispersed with a monochromator and detected using a liquid nitrogen cooled Si CCD (WSe 2 and MoSe 2 ) or InGaAs array (MoTe 2 ). During the measurements, the configuration of QWP-polarizer assembly is kept fixed, producing one state of circular polarization, whereas the effect corresponding to the other polarization state can be measured by reversing the direction of magnetic field, as a result of the time reversal symmetry [11,29].…”

Pressure-Induced Reversible Amorphization in Hydrogen-Bonded Crystalline Phenyl Carbamate Form-I

“…An amorphous solid crystallizes under high pressure because its excess free volume is distributed throughout the substance and is consequently released during crystallization. PIA is a prevalent phenomenon in numerous compounds, − and bondings in PIA systems vary widely in accordance with the material system. For example, bonds in SiO 2 are covalent, whereas those in Ca­(OH) 2 systems are ionic .…”

Reversible switching between pressure-induced amorphization and thermal-driven recrystallization in VO2(B) nanosheets

“…In some cases, mechanical instability caused by ‘thermodynamic melting' and increased atomic coordination are considered to contribute most to PIA 8 13 . While in other cases, such as ZrW 2 O 8 , negative thermal expansion (NTE) may have some possible connection with the PIA 14 15 16 17 . However, determining the underlying mechanism still remains one of the most fascinating challenges and some recent evidence even shows that previously reported PIAs were due to the fragmentation of bulky particles into nanocrystals and strongly correlated pressurization environments 3 .…”