Effect of fluoropolymer composition on topochemical synthesis of SrMn O3-δ Fγ oxyfluoride films

Jiayi Wang, Yongjin Shin, Elke Arenholz, Benjamin M. Lefler, James M. Rondinelli, Steven J. May

Research output: Contribution to journalArticlepeer-review

15 Scopus citations

Abstract

We report the synthesis of SrMnO3-δFγ perovskite oxyfluoride thin films using a vapor transport method to fluorinate as-grown SrMnO2.5 epitaxial thin films. The influence of the fluoropolymer, which acts as a fluorine vapor source, was investigated by utilizing polyvinyl fluoride (PVF), polyvinylidene difluoride (PVDF), and polytetrafluoroethylene (PTFE) in the reaction. The same process was carried out with polyethylene to isolate the role of carbon in the vapor transport process. The F distribution was probed by x-ray photoemission spectroscopy, which confirmed the incorporation of F into the films and revealed higher F concentrations in films exposed to PVF and PVDF compared to PTFE. The c-axis parameter expands after fluorination, a result consistent with density functional theory calculations that attribute the volume expansion to elongated Mn-F bonds compared to shorter Mn-O bonds. Using x-ray absorption spectroscopy, we show that the fluorination process reduces the nominal Mn oxidation state suggesting that F substitutes on O sites in the lattice as opposed to filling anion vacancy sites, a finding further supported by calculated formation energies of different F site occupancies. These results provide insights into topochemical fluorination of perovskite oxides, which should enable future synthesis and design efforts focused on oxyfluoride heterostructures.

Original languageEnglish (US)
Article number073407
JournalPhysical Review Materials
Volume2
Issue number7
DOIs
StatePublished - Jul 31 2018

ASJC Scopus subject areas

  • Materials Science(all)
  • Physics and Astronomy (miscellaneous)

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