Oxygen-ion and proton transport in Ba4Na2W2O11

►Perovskite-related tungstate of Ba4Na2W2O11 with oxygen deficiency as proton conductor. ►The phase is capable of dissociative dissolution of water and can exhibit proton transport below 500 °C. ►Localization of protons on oxygen leads to different forms of oxygen-hydrogen groups: OH− and H3O+ groups.