Ammonothermal Synthesis of Ba2PO3N – An Oxonitridophosphate with Non-Condensed PO3N Tetrahedra

Abstract

The ortho-oxonitridophosphate Ba2PO3N was synthesized under ammonobasic conditions (T = 1070 K, p = 120 MPa) in custom-built high-temperature autoclaves, starting from red phosphorus, BaO, NaN3 and KOH. Thus, single crystals of up to several hundred µm were obtained, which were used for single-crystal X-ray diffraction. Ba2PO3N [Pnma (no. 62), a = 7.596(2), b = 5.796(1), c = 10.212(3) Å, Z = 4] crystallizes in the β-K2SO4 structure type with non-condensed [PO3N]4– ions and is isotypic to its lighter homologues EA2PO3N (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. Eu2+ doped samples show green luminescence (λem = 534 nm, fwhm = 85 nm/2961 cm–1) when irradiated with UV light (λexc = 420 nm). However, Ba2PO3N:Eu2+ shows strong thermal quenching, even at room temperature.