Electronic structure of the monoclinic and hexagonal trioxides of tungsten and hexagonal hydrogen tungsten bronze H0.24WO3

The methods of x-ray photoelectron spectroscopy (XPS) and x-ray emission spectroscopy (XES) were used to study the electronic structure of the monoclinic and hexagonal modifications of WO₃, as well as hexagonal hydrogen tungsten bronze H_0.24WO₃. The OKα emission bands and the XPS spectra of the valence and core electrons were obtained for all of the compounds. It is shown that the half-width of the OKα bands and the XPS spectra of the valence electrons increase in the modification sequence WO₃ → hexagonal WO₃ → H_0.24WO₃. The near-Fermi region of the XPS valence-electron spectrum of the compound H_0.24WO₃ was found to contain an additional subband that is absent from both modifications of WO₃. It was established that, within the experimental error, the binding energies of the W4f and O1s core electrons remain constant for all of the compounds that were studied. Translated from Poroshkovaya Metallurgiya, Nos. 5–6(413), pp. 82–91, May–June, 2000.     

First-principles study of structure,mechanical and optical properties of La-and Sc-doped Y_2O_3

The electronic,mechanical and optical properties of La-and Sc-doped Y_2O_3 were investigated using firstprinciples calculations.Two doping sites of Sc and La in Y_2O_3 were modeled.The calculated values of the energy of formation show that the most energetically favorable site for a La atom in Y_2O_3 is a d-site Y atom,while for Sc a b-site Y atom is the more stable position.The calculated band gap shows a slight decrease with increasing La or Sc concentration.The calculated results for the mechanical and optical properties of Y_(2-x)R_xO_3(R = Sc or La,0x ≤ 0.1875)show that La-or Sc-doped Y_2O_3 would have enhanced strength,and thus an ability of resisting external shocks,and increased hardness and mechanical toughness.These improved mechanical properties are achieved without sacrificing the optical properties of the doped compounds.So the doping of La or Sc in Y_2O_3 is permissible in the preparation of Y_2O_3 transparent ceramics,of course,doping of La or Sc will benefit the sintering of transparent ceramics.