On the Crystal Structure and Conductivity of Na3P

As a potential material for Na‐ion battery systems and on the basis of a structural discussion of compounds formerly believed to crystallize in the so‐called Na 3 As type the structure of Na 3 P has been reinvestigated. Na 3 P is found to crystallize in the Cu 3 P type, analogous to Na 3 As and is described by a three times larger unit cell [ P 6 3 cm, a = 8.61224(10) Å and c = 8.81949(10) Å] compared to the former model [ P 6 3 / mmc, a = 4.9512(5) Å and c = 8.7874(13) Å]. As a structural manifestation of this symmetry reduction corrugated layers of Na and P atoms are observed which had formerly to be described as planar. The high purity of the material further enables the determination of its properties, showing mainly semiconducting behavior with a conductivity of 12 S · cm –1 at room temperature.