Order and Disorder in Mixed (Si, P)–N Networks Sr₂SiP₂N₆:Eu²⁺ and Sr₅Si₂P₆N₁₆:Eu²⁺

Abstract In the field of nitride phosphors, which are crucial for phosphor‐converted light‐emitting diodes, mixed tetrahedral networks hold a significant position. With respect to the wide range of compositions, the largely unexplored (Si, P)–N networks are investigated as potential host structures. In this work, two highly condensed structures, namely Sr₂SiP₂N₆ and Sr₅Si₂P₆N₁₆ are reported to address the challenges that arise from the similarities of the network‐forming cations Si⁴⁺ and P⁵⁺ in terms of charge, ionic radius, and atomic scattering factor, a multistep workflow is employed to elucidate their structure. Using single‐crystal X‐ray diffraction, energy‐dispersive X‐ray spectroscopy (EDX), atomic‐resolution scanning transmission electron microscopy (STEM)‐EDX maps, and straightforward crystallographic calculations, it is found that Sr₂SiP₂N₆ is the first ordered, and Sr₅Si₂P₆N₁₆ the first disordered, anionic tetrahedral (Si, P)–N network. After doping with Eu²⁺, Sr₂SiP₂N₆:Eu²⁺ shows narrow cyan emission (λ_max = 506 nm, fwhm = 60 nm/2311 cm⁻¹), while for Sr₅Si₂P₆N₁₆:Eu²⁺ a broad emission with three maxima at 534, 662, and 745 nm upon irradiation with ultraviolet light is observed. An assignment of Sr sites as probable positions for Eu²⁺ and their relation to the emission bands of Sr₅Si₂P₆N₁₆:Eu²⁺ is discussed.