The crystal structure, thermal behaviour and ionic conductivity of a novel lithium gadolinium polyphosphate LiGd(PO3)4

Crystal structure and ionic conductivity of lithium gadolinium polyphosphate, LiGd(PO3)4, were investigated. Single crystals of the title compound have been grown by a flux technique. The structure of this novel phosphate was determined by single crystal X-ray diffraction techniques. LiGd(PO3)4 is isotypic with LiNd(PO3)4. It crystallizes in the monoclinic space group C2/c with the unit cell parameters a=16.386(2), b=7.059(3), c=9.677(2) Å, β=126.12(1)°, V=904.2(4) Å3 and Z=4. The structure refined from 967 independent reflections leads to R1=0.0167 and wR2=0.0458. The lattice of LiGd(PO3)4 is built of twisted zig–zag chains running along with the b direction and make up of PO4 tetrahedra sharing two corners, connected to the GdO8 and LiO4 polyhedra by common oxygen atoms to form a three-dimensional framework. Differential and thermogravimetric thermal analysis are given. The thermal curve of this compound was recorded and interpreted in agreement with impedance measurements. The ionic conductivity has been measured on pellet of the polycrystalline powder and evaluated as a function of temperature. This phase showed the conductivity of 2×10−6 and 2×10−4 Ω−1 cm−1 at 682 and 951 K, respectively.