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 (λmax = 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.