Robert L Green
Florida Polytechnic University, USA
Title: Synthesis and structural characterization of the hexagonal anti-perovskite Na2CaVO4F
Biography
Biography: Robert L Green
Abstract
A high-resolution neutron powder diff raction technique was used to observe and refi ne the structural details of the ordered hexagonal oxyfl uoride Na2CaVO4F. Polycrystalline samples were prepared via solid-state synthesis using stoichiometric amounts of high pure starting materials. Th e structural changes between 25°C and 750°C revealed that the two structural subunits contained within this material exhibit diff erent behavior when heated. Th ere is an expansion of the face-shared FNa4Ca2 octahedra while the VO4 tetrahedra due to increased thermal disorder reveal marginal bond contractions. Th e bond valence method is employed to compare observed and ideal bond distances and point to a structural instability at 750oC. Th e Echidna high-resolution powder diff ractometer located at the OPAL Research Reactor of the Australian Nuclear Science and Technology Organization (ANSTO) was used for both room temperature and temperature-dependent studies whereby diff raction data was collected using a neutron beam with a wavelength of 1.6215(1) Å using a Ge (335) monochromator. All preliminary structural information was collected using a benchtop X-ray diff ractometer using Cu-Kα (1.54059 Å) over the range of 3-149° 2-theta. Both X-ray and neutron diff raction data was refi ned using the GSAS suite of programs.