A new alkali metal-rare earth polyphosphates NaGd(1-x)Eux(PO3)4 (x= 0, 0.05, 0.10, 0.15) were prepared by solid state reaction. The obtained powders are identified by X-ray diffraction, Raman and Infrared spectroscopies. These polyphosphates crystallize in the monoclinic system with P 21/n space group and with cell parameters a= 7.174(1)Å, b= 13.033(2)Å, c= 9.781(1)Å, β= 90.65(2)°, V= 914.47(20)Å3 and Z= 4. The structure of NaGd(PO3)4 is both (PO4)3- zig-zag chains and an infinite chains formed by the alternate connection of GdO8 polyhedra and LiO4 tetrahedra. The compound has good thermal stability to 920°C. Magnetic susceptibilities of single crystals were measured in the temperature range of 5-300 K. The compounds were paramagnetic, and obeyed the Curie-Weiss law in the entire temperature interval, without magnetic phase transitions. Optical properties of the Eu3+ doped NaGd(PO3)4 were investigated under λex= 394 nm and λem= 591 nm at 300K. The excitation spectra have revealed from 200 to 350 nm the presence of Gd3+ 4f-5d interconfiguration transitions, Gd3+– O2- and Eu3+– O2- charge transfer states (CTS) in addition to intraconfiguration transitions of Gd3+ ions. Eu3+ doped phosphors can emit intense reddish orange light. The strongest two at 590 and 613 nm can be attributed to the transitions from excited state 5D0 to ground states 7F1 and 7F2, respectively.
S. Hammami, N. Chniba Boudjada, A. Megriche
NGP polyphosphates, Infrared spectroscopy, magnetic properties, Optical materials, Raman spectroscopy