Multicationic Tetrahedra Networks: Alkaline‐Earth‐Centered Polyhedra and Non‐Condensed AlN6‐Octahedra in the Imidonitridophosphates AE2AlP8N15(NH) (AE=Ca, Sr, Ba).

A series of isostructural imidonitridophosphates AE2AlP8N15(NH) (AE=Ca, Sr, Ba) was synthesized at high‐pressure/high‐temperature conditions (1400 °C and 5–9 GPa) from alkaline‐earth metal nitrides or azides Ca3N2/Sr(N3)2/Ba(N3)2 and the binary nitrides AlN and P3N5. NH4F served as a hydrogen source and mineralizing agent. The crystal structures were determined by single‐crystal X‐ray diffraction and feature a three‐dimensional network of vertex‐sharing PN4‐tetrahedra forming diverse‐sized rings that are occupied by aluminum and alkaline earth ions. These structures represent another example of nitridophosphate‐based networks that simultaneously incorporate AlN6‐octahedra and alkaline‐earth‐centered polyhedra, with aluminum not participating in the tetrahedra network. They differ from previously reported ones by incorporating non‐condensed octahedra instead of strongly condensed octahedra units and contribute to the diversity of multicationic nitridophosphate network structures. The results are supported by atomic resolution EDX mapping, solid‐state NMR and FTIR measurements. Eu2+‐doped samples show strong luminescence with narrow emissions in the range of green to blue under UV excitation, marking another instance of Eu2+‐luminescence within imidonitridophosphates. [ABSTRACT FROM AUTHOR]