(Dis)Order and Luminescence in Silicon-Rich (Si,P)-N Network Sr 5 Si 7 P 2 N 16 :Eu 2 .

In this work, we present the synthesis, characterization, and optical properties of Sr 5 Si 7 P 2 N 16 :Eu 2+ , the first tetrahedral (Si,P)-N network in which Si occupies more than 50% of the tetrahedra. While past studies have shown progress with anionic (Si,P)-N networks, the potential of silicon-rich compounds remains untapped. The synthesized compound Sr 5 Si 7 P 2 N 16 exhibits a unique mixture of substitutional order and positional disorder within its network. The analytical challenges posed by the similarities between Si 4+ and P 5+ , along with the network's disorder, were overcome by combining single-crystal X-ray diffraction and scanning transmission electron microscopy EDX mapping. Low-cost crystallographic calculations provided additional insights into the identification of tetrahedral occupations in mixed networks. Luminescence investigations on Sr 5 Si 7 P 2 N 16 :Eu 2+ revealed yellow emission, adding to the known blue, green, and orange emission maxima of Sr-(Si,P)-N networks, highlighting the variability of such compounds.