Unconventional vapor–liquid–solid mechanism of ultra-long Ba6Mn24O48 whiskers growth from chloride fluxes

Abstract

Isothermal growth in evaporating salt fluxes allowed the reproducible and high-yield synthesis of unique submicron-thick and millimeter-long manganese-rich Ba 6 Mn 24 O 48 whiskers with a composite tunnel crystal structure. The crystals morphology and growth conditions suggest that the whiskers proliferate by an unusual mechanism based on a transport reaction of MnCl 2 vapor, its oxidation into manganese oxides and interaction with a BaCl 2 -containing melt film wetting the whisker bodies. Thin fibers of Ba 6 Mn 24 O 48 were found to grow mostly in the [001] direction parallel to their structural tunnels. A simple acid leaching splits the whiskers into flexible 20-50 nm thick nanofibers and converts them simultaneously into a protonated form favoring one-dimensional ionic conductivity.