We present the first nitridic analogs of micas, namely AESi3 P4 N10 (NH)2 (AE=Mg, Mg0.94 Ca0.06 , Ca, Sr), which were synthesized under high-pressure high-temperature conditions at 1400 °C and 8 GPa from the refractory nitrides P3 N5 and Si3 N4 , the respective alkaline earth amides, implementing NH4 F as a mineralizer. The crystal structure was elucidated by single-crystal diffraction with microfocused synchrotron radiation, energy-dispersive X-ray spectroscopic (EDX) mapping with atomic resolution, powder X-ray diffraction, and solid-state NMR. The structures consist of typical tetrahedra-octahedra-tetrahedra (T-O-T) layers with P occupying T and Si occupying O layers, realizing the rare motif of sixfold coordinated silicon atoms in nitrides. The presence of H, as an imide group forming the SiN4 (NH)2 octahedra, is confirmed by SCXRD, MAS-NMR, and IR spectroscopy. Eu2+ -doped samples show tunable narrow-band emission from deep blue to cyan (451-492 nm).
Keywords: Electron microscopy; High-pressure; Mica; Nitride; Synchrotron.
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