Remarkably high proton conductivity in cubic perovskite-related Ba3WO6

The Ba3WO6 material was reported to have seven kinds of polymorphs. However, the crystal structures of most of them were not established. In this work, the polymorph (denoted as alpha-Ba3WO6 hereafter) with a cubic 4 x 4 x 4 superstructure of a simple perovskite structure was prepared, with its crystal structure being solved by combining powder X-ray diffraction (XRD) and neutron powder diffraction (NPD) techniques. This structure showed intrinsically severe barium- and oxygen-deficiencies. Variable temperature XRD revealed a phase unstable region within 600-1000 degrees C. The electrical property study on alpha-Ba3WO6 revealed extremely high proton conductivities at temperatures below 600 degrees C, e.g. 1.75 x 10(-2) S cm(-1) at 500 degrees C, which is comparable to that of the BaCeO3-based materials. A fuel cell based on alpha-Ba3WO6 electrolyte yielded a power density of similar to 520 mW at a working temperature of 500 degrees C. The alpha-Ba3WO6 material thus shows great potential for being used as an electrolyte for proton conducting fuel cells (PCFCs). This work thus may further stimulate the development of superior proton conductors in oxides with a superstructure of the simple perovskite structure.