X-ray diffraction, super(31)P NMR and europium photoluminescence properties of the Na sub(2)Ba sub(1-) sub(x)Sr sub(x)Mg(PO sub(4)) sub(2) system related to the glaserite type structure

• Published in: Journal of molecular structure 2015-03, Vol.1083, p.319-329
• Main Authors: Boukhris, Amal, Glorieux, Benoit, Amara, Mongi Ben
• Format: Article
• Language: English
• Subjects: Cationic; Diffraction; Europium; Molecular structure; Photoluminescence; Samples; Statistical analysis; Statistical methods; Symmetry
• ISSN: 0022-2860
• DOI: 10.1016/j.molstruc.2014.11.063

Different samples of a solid solution of glaserite-type structure with the general formula Na sub(2)Ba sub(1-) sub(x)Sr sub(x)Mg(PO sub(4)) sub(2)(0 [el] x [el] 1) were synthesized by the Pechini method and characterized by X-ray powder diffraction (XRD), super(31)P NMR spectroscopy and photoluminescence of europium doped compounds. The XRD patterns show that Na sub(2)Ba sub(1-) sub(x)Sr sub(x)Mg(PO sub(4)) sub(2) system adopts the trigonal symmetry with the space group of P m1 for 0 [el] x [el] 0.55 while from x = 0.6, it crystallizes in the monoclinic symmetry with the space group P2 sub(1)/a. The four resonances observed in the super(31)P NMR spectra for each composition of the system Na sub(2)Ba sub(1-) sub(x)Sr sub(x)Mg(PO sub(4)) sub(2) (0 [el] x [el] 1) are interpreted on the basis of four configurations of statistical distribution (Ba super(2+)/Sr super(2+)) in the neighboring cationic sites of a PO sub(4) tetrahedron. The photoluminescence of doped samples with divalent and trivalent europium was analyzed according to their compositions. Evolution of the super(31)P chemical shift for each cationic configuration around PO sub(4) tetrahedra versus the composition x.