High temperature gaseous rare-earth permeation of polyoxotungstates: An new effective method for the preparation of tungsten bronzes

New polyoxometalate α-K12H3[Y(BW11O39)2]·25H₂O was synthesized and treated by high temperature gaseous rare earth permeation to prepare tungsten bronze K_0.475WO₃. XRD, TG-DTA, XPS, ¹⁸³W-NMR,CV and AC impedance spectra were used to characterize the resulting material . The results of XPS indicate that La has permeated and diffused into the body of the sample and exists in the forms of binding with other components. The crystal structure parameters of K_0.475WO₃ were obtained by the analysis of XRD, which shows tetragonal crystal system with lattice parameters: a=12.28 nm, c=3.833 nm, V=578.48 nm^-3. The conductivities calculated from the results of AC impedance spectra of the material increase with the increasing of temperature, which shows a semiconductor character.