Four-Dimensional Incommensurate Modulation and Luminescent Properties of Host Material NaLa(PO).

A series of orthophosphates NaLn(PO) (Ln = lanthanoids) have for a long time been known as good luminescent materials, yet their crystal structures have not been studied in full detail. In this work, compound NaLa(PO) was prepared using molten salt (flux) method and for the first time was structurally determined on X-ray single-crystal diffraction data. Interestingly, it crystallizes in the four-dimensional incommensurately modulated structure with orthorhombic superspace group Pca2(0β0)000 and modulation wave vector q = 0.387b*. Furthermore, to evaluate the potentiality of NaLa(PO) to be used as a luminescent host material, 5 mol % Eu, Tb, and Dy doped phosphors were prepared, respectively. The excitation spectra, emission spectra, decay time, quantum efficiency, and the color purity of prepared phosphors, NaLaEu(PO), NaLaTb(PO), and NaLaDy(PO), were studied.