Tunable Narrow‐Band Cyan‐Emission of Eu2+‐doped Nitridomagnesophosphates Ba3–xSrx[Mg2P10N20]:Eu2+ (x = 0–3)

Tetrahedron‐based nitrides offer a wide range of properties and applications. Highly condensed nitridophosphates are examples of nitrides exhibiting fascinating luminescence properties when doped with Eu2+, making them appealing for industrial applications. We present the first nitridomagnesophosphate solid solution series Ba3–xSrx[Mg2P10N20]:Eu2+ (x = 0–3), synthesized by a high‐pressure high‐temperature approach using the multianvil technique (3 GPa, 1400 °C). Starting from the binary nitrides P3N5 and Mg3N2 and the respective alkaline earth azides, we incorporate Mg into the P/N framework to increase the degree of condensation κ to 0.6, the highest observed value for alkaline earth nitridophosphates. The crystal structure was elucidated by single‐crystal X‐ray diffraction, powder X‐ray diffraction, energy‐dispersive X‐ray spectroscopy (EDX), and solid‐state NMR. DFT calculations were performed on the title compounds and other related highly condensed nitridophosphates to investigate the influence of Mg in the P/N network. Eu2+‐doped samples of the solid solution series show a tunable narrow‐band emission from cyan to green (492–515 nm), which is attributed to the preferred doping of a single crystallographic site. Experimental confirmation of this assumption was provided by overdoping experiments and STEM‐HAADF studies on the series as well on the stoichiometric compound Ba2Eu[Mg2P10N20] with additional atomic resolution energy‐dispersive X‐ray spectroscopy (EDX) mapping.