Structural transitions in Cu₂O at pressures up to 11 GPa

Abstract

The structural states of Cu2O at pressures between ambient and 11 GPa were re-investigated, using angle-dispersive diffraction, an area detector and synchrotron radiation. Thanks to the latter’s naturally high collimation, a hitherto suspected transition from the parent cubic phase to a new tetragonal phase was experimentally confirmed at pressures between 0.7 and 2.2 GPa, depending on the hydrostaticity of the pressure medium used. The other transformation, into a pseudocubic phase, was detected at about 8.5 GPa. In the same pressure range, the application of pressure also resulted in a general and strong broadening of the diffraction peaks. This broadening is attributed to the presence of microscopic strains and a reduction in grain size down to the nanocrystalline scale.

Framework flexibility and the negative thermal expansion mechanism of copper(I) oxideCu2O

“…This transition was observed to be proper ferroelastic in nature and the new phase was identified as tetragonal 54 as opposed to our prediction of an orthorhombic phase. Curiously, the structure was also observed to transform into a pseudocubic phase at 8.5 GPa.…”

High pressure densification and dielectric properties of perovskite-type oxynitride SrTaO2N

“…Similar diffraction line broadening has been reported for oxides, nitrides and carbides, where the grain size was reduced to the nanometer scale under microstructural strain [13,23,24]. The electron diffraction shown in Fig.…”

Influence of target power on properties of CuxO thin films prepared by reactive radio frequency magnetron sputtering

“…Similarly, D p from the Cu 2 O (200) peak increases from 14 to 20 nm as P tar is increased from 160 to 190 W. Ponyatovskii et al [19] studied the effect of high external pressure on the structure of Cu 2 O and revealed a phase transition to CuO accompanied by a decrease in grain size. Machon et al [20] also obtained similar results and attributed these effects under high pressure to a considerable increase in the microstrain within the film. In contrast, we observe the opposite effects for both phase transition and D p and therefore, a decrease in the compressive microstrain of the Cu 2 O films with increasing P tar is anticipated.…”