Nontypical Luminescence Properties and Structural Relation of Ba₃P₅N₁₀X:Eu²⁺ (X = Cl, I): Nitridophosphate Halides with Zeolite-like Structure

The isotypic nitridophosphates Ba 3 P 5 N 10 X (X = Cl, I) have been synthesized by high-temperature reaction under pressures between 1 and 5 GPa. The crystal structures of both compounds were solved and refined using single-crystal X-ray diffraction data. Accuracy of the structure determination as well as phase purity of the products were confirmed by Rietveld refinement and FTIR spectroscopy. The band gap values (4.0–4.3 eV) for the direct transitions were determined from UV–vis data using the Kubelka–Munk function and were confirmed by DFT calculations. Both compounds crystallize in the Ba 3 P 5 N 10 Br structure type (space group Pnma (No. 62), Z = 8; Ba 3 P 5 N 10 Cl, a = 12.5182(5) Å, b = 13.1798(5) Å, c = 13.7676(6) Å, R 1 = 0.0214, wR 2 = 0.0526; Ba 3 P 5 N 10 I, a = 12.6311(7) Å, b = 13.2565(8) Å, c = 13.8689(8) Å, R 1 = 0.0257, wR 2 = 0.0586) with a tetrahedra network being analogous to the topology of the JOZ zeolite structure type. The crystal structure is built up of all-side vertex-sharing PN 4 tetrahedra leading to a zeolite-like framework with three-dimensional achter -ring channels containing alternately Ba and respective halide atoms. The condensed dreier -, vierer -, and sechser -rings form two different composite building units made up of 3 4 4 2 8 6 -cages. Upon being doped with Eu 2+, the title compounds exhibit intriguing luminescence properties, which were compared with that of Ba 3 P 5 N 10 Br:Eu 2+ . Upon excitation by near-UV light, nonsaturated color luminescence from multiple emission centers was observed in the orange (X = Cl) and cyan to amber (X = I) spectral range of the visible spectrum.