PHYSICAL-CHEMICAL CHARACTERIZATION OF PHOSPHATETUNGSTEN BRONZE DOPED WITH IRON FROM HETEROPOLY SALTS AS PRECURSORS

Abstract

Heteropolyacids, with a general formula ofH3+xAM12O40∙nH2O (x=0-1; A=P, Si, B, As, Ge;M=Mo, W; n=30-6) are of special interest as newmaterials because of their high conductivities. Among them special attention deserves the 12-tungstophosphoric (29- WPA) acid. Heteropolies of acids and salts heteropolises of acids can also be used as starting materials for the production of tungsten bronzes. These bronzes have a specific structure that results from the collapse of the Kegin anion at a temperatures up to 602 0C. This structure is layered and consists of interconnected PO4tetrahedra and WO6octahedra. In such a structure, pentagonal and hexagonal openings (cavities, channels) are formed in which there is a complete or partial exchange of H+ ions in WPA. In this paper, 12-tungstenphosphoric acid was synthesized, ion exchange gave 12-tungstenphosphoric acid of the transition metal (FePW12O40 ∙ nH2O). Thermal analysis determined the temperature of the phase transition (the temperature at which the structure of the Kegin anion is disturbed) at a temperature (about 600 0C) to obtain phosphate tungsten bronzes doped with iron. Physico-chemical methods IR, XRPD and SEM were used to characterize the material. Due to their ionic and electronic conductivity and other useful properties, heteropoly compounds have wide application: as new materials, superionic conductors, in biology, pharmacy and medicine. This paper presents a new contribution to the elucidation of problems related to structure, identification of conductive species and examination of WPA phase transformations to bronze formation by different methods and design of obtained structures, and our further research will be directed in these directions.