Na2BaMg(PO4)2: synthesis, crystal structure and europium photoluminescence properties

Na2BaMg(PO4)2 was synthesized and characterized by X-ray diffraction, differential thermal analysis (DTA), 31P NMR spectroscopy and photoluminescence measurements. This compound crystallized in the P imagem1 space group of the trigonal system with the parameters of equivalent hexagonal cell a=0.5305(1) nm and c=0.6986(3) nm. The structure showed a perfect isotipysm with the mineral glaserite K3Na(SO4)2. Thus, it exhibited a lamellar framework which could be described as the stacking along the [001] direction of [MgP2O84−]∞ layers of corner sharing MgO6 polyhedra and PO4 tetrahedra. The Ba2+ cations were located within the interlayer space, while the Na+ ones were found in large cavities bound to the layers. The DTA analysis showed that this compound melt congruently at 1385 K. The 31P NMR spectrum was consistent with the presence of a single phosphorus site in the structure. Optical properties were investigated for the 5% doped Eu3+ and Eu2+ phases. The trivalent europium was used as a local probe, replacing barium while the divalent europium was used to examine whether this material could be used as an optical applications.