Morphology and Conductivity of Copper Hexacyanoferrate Films

Abstract

Films of conductive coordination network compounds are interesting as functional materials for charge storage, electrocatalysis, electrochromic switching, or conversion of light. The electrical conductivity depends on not only intrinsic material properties but also grain boundaries. Copper hexacyanoferrate shows a remarkable variation in film morphologies depending on the preparation route. Conductive films can only be obtained for continuous crystalline films that have been received by a combination of sonication-assisted casting and vapor-assisted conversion. Electrical conductivities of these films are higher than those of powder pellets with a similar crystal structure. Temperature-dependent and humidity-dependent measurements on powder pellets revealed the activation energies for charge transport. Thermogravimetric analysis, temperature-dependent X-ray diffraction data, and humidity-dependent measurements on powder pellets revealed the activation energies for charge transport and the role of proton conductivity.

Resistive Switching in Electrodeposited Prussian Blue Layers

“…For HRS, a much lower activation energy of 0.03 eV was obtained. The activation energy for the LHS is similar to the one of 0.27 eV for the conduction in Cu II [Fe III (CN) 6 ] 2/3 ·nH 2 O in dry atmosphere obtained by Hosseini et al [ 36 ]. The authors studied the intrinsic conduction in copper hexacyanoferrates and attributed the activation energies to the proton hopping mechanism.…”

Exploration of glassy state in Prussian blue analogues

“…It can be classified as ranging from semiconductive in PBAs with a relatively narrow bandgap 40 to nearest-neighbour hopping due to the localised 3 d electron in Fe[Fe] 3/4 and Berlin green with band insulator characteristics (10 −7 to 10 −11 S cm −1 ) 41 . A relatively low ligand-field splitting predicted for Cu-hexacyanoferrate among the metal hexacyanoferrates makes it a suitable candidate to elucidate the electronic conductivity in a glassy state 42 . The transport mechanism can be classified as class II mixed-valence compounds according to Robin−Day, where charges transfer between localised charge carriers through thermally activated electron hopping 40 , 43 , 44 .…”

Exploration of glassy state in Prussian blue analogues

“…It can be classified as ranging from semiconductive in PBAs with a relatively narrow bandgap 53 to nearest-neighbour hopping due to the localized 3d electron in Fe[Fe]3/4 and Berlin green with band insulator characteristics (10 −7 to 10 −11 S cm −1 ) 54,55 . A relatively low ligand-field splitting predicted for Cu-hexacyanoferrate among the metal hexacyanoferrates makes it a suitable candidate to elucidate the electronic conductivity in a glassy state 56 . The transport mechanism can be classified as class II mixed-valence compounds according to Robin−Day, where charges transfer between localized charge carriers through thermally activated electron hopping 53,[57][58][59] .…”