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

The isotypic nitridophosphates Ba3P5N10X (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 Ba3P5N10Br structure type (space group Pnma (No. 62), Z = 8; Ba3P5N10Cl, a = 12.5182(5) angstrom, b = 13.1798(5) angstrom, c = 13.7676(6) angstrom, R1 = 0.0214, wR2 = 0.0526; Ba3P5N10I, a = 12.6311(7) angstrom, b = 13.2565(8) angstrom, c = 13.8689(8) angstrom, R1 = 0.0257, wR2 = 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 PN4 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 Eu2+, the title compounds exhibit intriguing luminescence properties, which were compared with that of Ba3P5N10Br:Eu2+. 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.