Synthesis, crystal structure, electrical and magnetic properties of a novel phosphate: Ag4CoFe2(PO4)4

A new silver-cobalt-iron orthophosphate, Ag4CoFe2(PO4)4, has been elaborated in single crystal and powder forms. The crystal structure was studied using X-ray diffraction data. This new phosphate crystallizes in the monoclinic system with C2/c space group. The structure of this phosphate consists of an association of FeO6 and CoO6 octahedra, and PO4 tetrahedra sharing corners and edges leading to infinite layers perpendicular to the [010] direction. Ag+ cations reside in the interlayer space and in the cavities of the crystal framework. Furthermore, the purity of the synthesized powder was validated by X-ray powder diffraction analysis. The bands observed in the infrared and Raman spectra were attributed to the vibration modes of the PO4 tetrahedra. The electrical conductivity of this phosphate was investigated using impedance spectroscopy. The results showed an ionic conductivity of 2.6 ​× ​10−3 ​S ​cm−1 at 773 ​K with an activation energy of Ea ​= ​1.17 ​eV indicating the Ag ​+ ​mobility in the layered structure. The magnetic investigation revealed antiferromagnetic order below the temperature of TN ∼10 ​K with a Curie-Weiss constant of Ө ​= ​−119.39 ​K.