Hexagonal Na1.5Y1.5F6 at High Pressures

High temperature X-ray diffraction studies on sodium yttrium fluoride

“…The pattern could be indexed on the basis of a hexagonal unit cell with a = 5.973(1) and c = 3.529(1) Å. These values are in good agreement with the reported ones [3,7]. The XRD pattern of NaYF 4 sample could be indexed on the basis of a unit cell with a = 5.499(1) Å, which compares well with the reported cell parameter [4][5][6]9].…”

“…Na 1.5 Y 1.5 F 6 was prepared by standard solid state synthesis route from an appropriate mixture of NaF and YF 3 as described elsewhere [7]. NaYF 4 was prepared by precipitation method [4] by adding a supersaturated aqueous solution of sodium fluoride to the aqueous solution of yttrium chloride.…”

“…Earlier, Sobolev et al [3] have shown by DTA studies that Na 1.5 Y 1.5 F 6 undergoes a phase transition into NaYF 4 with cubic symmetry at ∼973 K. Recently, based on the high pressures and high temperatures studies on NaYF 4 , Grzechnik et al [7] have reported that this compound undergoes a phase transition into a new polymorph with gagarinite type structure, which decomposes on further heating. These observations together with the results of the present studies indicate that the temperature profile and the experimental conditions have a pronounced effect on the high temperature behaviour of both the compounds.…”

“…The information about the chemical bonding and interaction between the central ions and their coordination spheres at different pressures and/or temperatures is required for understanding various optical properties. Our recent studies [7] on the high pressure behaviour of hexagonal Na 1.5 Y 1.5 F 6 using synchrotron X-ray powder diffraction (XRD) up to 22 GPa at room temperature showed that above 20 GPa pressure-induced order-disorder phenomena led to the formation of gagarinite type structure of the compound. Very recently, Grzechnik et al [8] have reported the behaviour of cubic NaYF 4 at high pressures and high temperatures.…”

Upconversion luminescence in Yb3+/Tb3+-codoped monodisperse NaYF4 nanocrystals

“…For example LiYF 4 , NaYF 4 , LiScF 4 have been investigated widely [17,18]. Among them, NaYF 4 has been recognized as the most efficient host lattice for UC systems due to its low phonon energy of about 370 cm À1 [19] and its ordering of the cations and their crystalline surrounding [17].…”