X-ray photoelectron spectroscopy (XPS) and magnetic susceptibility studies of vanadium phosphate glasses

• Published in: Journal of non-crystalline solids Vol. 355; no. 43; pp. 2148 - 2155
• Main Authors: Khattak, G.D., Mekki, A., Wenger, L.E.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier B.V 15.10.2009; Elsevier
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Disordered solids; Disordered structures; Electron and ion emission by liquids and solids; impact phenomena; Exact sciences and technology; Glasses; Magnetic properties; Magnetic properties and materials; Magnetically ordered materials: other intrinsic properties; Oxide glasses; Phosphates; Photoemission and photoelectron spectra; Physics; Saturation moments and magnetic susceptibilities; Structure of solids and liquids; crystallography; XPS; Phosphates; 61.05.js; 75.20.-g; Oxide glasses; XPS; 61.43.Fs; Magnetic properties; Magnetization; Curie-Weiss law; Binary systems; Glass structure; Phosphate glass; Core levels; Magnetic susceptibility; Valence; Asymmetry; Vanadates; Spin-orbit interactions; Chemical composition; Energy-level splitting; X-ray photoelectron spectra
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/j.jnoncrysol.2009.06.042

Vanadium phosphate glasses with the nominal chemical composition [(V 2O 5) x (P 2O 5) 1− x ], where x = 0.30, 0.40, 0.50, and 0.60, have been prepared and investigated by X-ray photoelectron spectroscopy (XPS) and magnetization measurements. Asymmetries found in the O 1s, P 2p, and V 2p core level spectra indicate the presence of primarily P–O–P, P–O–V, and V–O–V structural bonds, a spin–orbit splitting of the P 2p core level, and more than one valence state of V ions being present. The magnetic susceptibility data for these glasses follow a Curie–Weiss behavior which also indicates the presence of some V ions existing in a magnetic state, i.e., a valence state other than that of the non-magnetic V 5+. From qualitative comparisons of the abundance of the bridging oxygen or P–O–P sites as determined from the areas under the various O 1s peaks with the abundances of differing phosphate structural groups associated with the presence of different valence states of the vanadium ions, a glass structure model consisting of a mixture of vanadate phosphate phases is proposed for these glass samples. These include V 2O 5, VOPO 4, (VO) 2P 2O 7, VO(PO 3), and V(PO 3) 3 with the abundance of orthophosphate (PO 4) 3− units increasing with increasing vanadium content.