XPS study on potassium tungsten bronze K _xLa _yWO ₃ prepared by rare earth co-permeation

Potassium tungsten bronze K _xLa _yWO ₃ (x>0.5 and y<0.01) was synthesized by rare earth co-permeation method using α-K ₇[SiMg ₃(OH ₂) ₃W ₉O ₃₇] as the precursor. Binding energies of La, W, O and C were determined by XPS. From the XPS data, a peak at 34.21 eV indicates that some W ⁶⁺ turned into W ⁵⁺ by rare earth co-permeation. The binding energies La3d were the same in the surface and inner of the composite, showing that rare earth element La could diffuse into the body of the composite and the compound of K _xLa _yWO ₃ was formed at the same time. The binding energies of O1s in K _xLa _yWO ₃ surface were 531.4 eV and 532.0 eV, respectively, while peak at 531.4 eV disappeared through etching process. The result implies that the binding energy of 531.4 eV was due to the adsorbent O. In addition, the binding energies of C1s in the surface were 283.5 eV, 285.0 eV and 286.7 eV respectively, while the inner had only one peak at 285.0 eV due to standard C1s. This proves that there was no C in the core.