Order and Disorder in Mixed (Si, P)–N Networks Sr<sub>2</sub>SiP<sub>2</sub>N<sub>6</sub>:Eu<sup>2+</sup> and Sr<sub>5</sub>Si<sub>2</sub>P<sub>6</sub>N<sub>16</sub>:Eu<sup>2+</sup>
Marwin Dialer, Monika M. Pointner, Sophia L. Wandelt, Philipp Strobel, Peter J. Schmidt, Lkhamsuren Bayarjargal, Björn Winkler, Wolfgang Schnick
Abstract
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 Sr 2 SiP 2 N 6 and Sr 5 Si 2 P 6 N 16 are reported to address the challenges that arise from the similarities of the network‐forming cations Si 4+ and P 5+ 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 Sr 2 SiP 2 N 6 is the first ordered, and Sr 5 Si 2 P 6 N 16 the first disordered, anionic tetrahedral (Si, P)–N network. After doping with Eu 2+ , Sr 2 SiP 2 N 6 :Eu 2+ shows narrow cyan emission ( λ max = 506 nm, fwhm = 60 nm/2311 cm −1 ), while for Sr 5 Si 2 P 6 N 16 :Eu 2+ 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 Eu 2+ and their relation to the emission bands of Sr 5 Si 2 P 6 N 16 :Eu 2+ is discussed.