Pressure-induced phase and chemical transformations of lithium peroxide (Li2O2) Journal Article uri icon

DCO ID 11121/8959-8824-4543-1864-CC

is Contribution to the DCO

  • YES

year of publication

  • 2016

abstract

  • We present the pressure-induced phase/chemical changes of lithium peroxide (Li2O2) to 63 GPa using diamond anvil cells, confocal micro-Raman spectroscopy, and synchrotron x-ray diffraction. The Raman data show the emergence of the major vibrational peaks associated with O2 above 30 GPa, indicating the subsequent pressure-induced reversible chemical decomposition (disassociation) in dense Li2O2. The x-ray diffraction data of Li2O2, on the other hand, show no dramatic structural change but remain well within a P63/mmc structure to 63 GPa. Nevertheless, the Rietveld refinement indicates a subtle change in the structural order parameter z of the oxygen position O (13/13, 23/23, z) at around 35 GPa, which can be considered as a second-order, isostructural phase transition. The nearest oxygen-oxygen distance collapses from 1.56 Å at ambient condition to 1.48 Å at 63 GPa, resulting in a more ionic character of this layered crystal lattice, 3Li++(LiO2)3−3Li++(LiO2)33−. This structural change in turn advocates that Li2O2 decomposes to 2Li and O2, further augmented by the densification in specific molar volumes.

volume

  • 145

issue

  • 8