Ammonothermal Synthesis of Ba 2 PO 3 N – An Oxonitridophosphate with Non‐Condensed PO 3 N Tetrahedra

The ortho ‐oxonitridophosphate Ba 2 PO 3 N was synthesized under ammonobasic conditions ( T = 1070 K, p = 120 MPa) in custom‐built high‐temperature autoclaves, starting from red phosphorus, BaO, NaN 3 and KOH. Thus, single crystals of up to several hundred µm were obtained, which were used for single‐crystal X‐ray diffraction. Ba 2 PO 3 N [ Pnma (no. 62), a = 7.596(2), b = 5.796(1), c = 10.212(3) Å, Z = 4] crystallizes in the β‐K 2 SO 4 structure type with non‐condensed [PO 3 N] 4– ions and is isotypic to its lighter homologues EA 2 PO 3 N ( EA = Ca, Sr). Powder X‐ray diffraction, energy dispersive X‐ray and Fourier Transformed Infrared spectroscopy corroborate the crystal structure. The optical band gap was determined by means of diffuse reflectance UV/Vis spectroscopy to be 4.3 eV. Eu 2+ doped samples show green luminescence ( λ em = 534 nm, fwhm = 85 nm/2961 cm –1 ) when irradiated with UV light ( λ exc = 420 nm). However, Ba 2 PO 3 N:Eu 2+ shows strong thermal quenching, even at room temperature.