The Phosphidosilicates AE 2 Li 4 SiP 4 (AE=Ca, Sr, Eu) Ba 4 Li 16 Si 3 P 12

The quaternary phosphidosilicates AE Li SiP (AE=Ca, Sr, Eu) and Ba Li Si P were synthesized by heating the elements and Li P under argon atmosphere. Their crystal structures were determined by single crystal X-ray diffraction. AE Li SiP crystallize in a new layered structure type (P2 /m, Z=2) with CdI -analoguos layers. Edge sharing CaP octahedra are separated by layers of vertex-sharing SiP and LiP tetrahedra, which contain additional chains of LiP octahedra. Ba Li Si P forms likewise a new structure type (P2 /c, Z=16) with a three-dimensional network of SiP , Si P and LiP entities as well as one phosphorus site not bonded to silicon. Barium is located in capped trigonal prisms of phosphorus which form strongly corrugated layers. P and Si solid-state NMR spectra confirm the crystal structures of the compounds AE Li SiP . Li spectra show only one signal in spite of quite different crystallographic positions, which indicate possible Li mobility. However, this signal is much broader compared to the known Li conducting phosphidosilicates. Accordingly, electrochemical impedance measurements show low Li conductivities.