Silver-gadolinium polytetraphosphate AgGd(PO 3) 4 synthesis, structural study, IR spectroscopy and conductivity investigation

Abstract

Crystals of a new silver-gadolinium, AgGd(PO 3) 4, have been synthesized for the first time by a flux method. The structure [monoclinic, P2 1/ n, a = 7.2378(2) Å, b = 13.0913(5) Å, c = 9.8136(4) Å, β = 90.494(1)°, V = 929.83(6) Å 3 and Z = 4] was solved by a three-dimensional Patterson function and refined to R 1 = 0.0399 ( w R 2 = 0.0885 ) on the basis of 3270 unique observed reflexions using 164 parameters. AgGd(PO 3) 4 is isostructural to NaLa(PO 3) 4, AgLa(PO 3) 4 and AgNd(PO 3) 4. The structure is based upon long chain polyphosphate running along the shortest unit-cell direction and made up of PO 4 tetrahedra (with a period of four tetrahedra) sharing two corners, linked to the polyhedra of gadolinium and silver by common oxygen atoms to the chains. This type of organisation gives rise to a three-dimensional framework. Gadolinium atoms have an eight-fold coordination while silver atoms have approximately six oxygen neighbours. Infrared spectrum of AgGd(PO 3) 4 at room temperature, investigated in the frequency range 400–1500 cm −1, confirms the atomic arrangement within the structure. The electrical conductivity of AgGd(PO 3) 4 has been measured on pellets of the polycrystalline powder and evaluated as a function of temperature. The conductivity of this phase was quite low and the values of 4.01 × 10 −7 and 1.10 × 10 −6 Ω −1 cm −1 were obtained at 803 and 873 K, respectively.