Vibrational and XRD Study of the System CdWO₄−CdMoO₄

Abstract

Mixed oxide powders belonging to the system CdMo x W1 - x O4 have been prepared by a hydrothermal method. They have been characterized by the Rietveld analysis of their XRD patterns and by IR and Raman skeletal spectroscopies. Virtually pure wolframite-type structures have been obtained for x ≤ 0.25 and virtually pure scheelite-type structures have been obtained for x ≥ 0.75. The vibrational spectra of both phases have been interpreted on the basis of the correlation method. In both solid solutions the Raman peaks due to the stretching modes of “terminal” W,Mo−O bonds split, while the corresponding IR bands shift significantly. The effect of the nature of tungsten coordination on the vibrational spectra is briefly discussed in relation to the use of vibrational spectroscopies to determine the structure of the surface species in supported tungsten oxide catalysts.

Density Functional Theory Calculations of 95Mo NMR Parameters in Solid‐State Compounds

“…Herein, we present calculations of EFG and CS tensors using PAW and GIPAW methods for a set of ternary molybdates of general formula AMoO 4 , where A is a divalent cation (Ba, [81] Pb, [82] Ca, [83] Sr, [84] Cd, [85] Zn [86] ), and A' 2 MoO 4 , where A' is a monovalent cation (K, [87] Cs, [88] Rb, [89] Na, [90] NH 4 [91] ). In all these compounds, molybdenum atoms have a + VI formal oxidation state and are coordinated to four oxygen atoms in a nearly tetrahedral symmetry (see Figure 1).…”

Anisotropy, phonon modes, and lattice anharmonicity from dielectric function tensor analysis of monoclinic cadmium tungstate

“…2 Raman spectra of CdWO 4 have been studied extensively, [6][7][8][9][10] and despite its use in detector technologies, investigation into its fundamental physical properties such as optical phonon modes, and static and highfrequency dielectric constants is far less exhaustive.…”

“…11 Blasse 6 investigated IR spectra of HgMoO 4 and HgWO 4 and also reported analysis of CdWO 4 in the spectral range of 200-900 cm −1 and identified 11 IR active modes but without symmetry assignment. Daturi et al 7 performed Fourier transform IR (FT-IR) measurements of CdWO 4 powder. An in- complete set of IR active modes was identified, and a tentative symmetry assignment was provided.…”

First‐principles study of electronic structures of CdMoO4 crystal containing F‐type color centers

“…In the work reported in this paper, in order to confirm the origin of the 650-750 nm absorption bands and the bluish green color, the CdMoO 4 crystal's F-type centers associated with oxygen vacancies were studied in detail. C (I4 /a) has two molecular units in the primitive cell with lattice parameters a = b = 0.5156 nm and c = 1.1196 nm [15] . The MoO 4 group has the shape of a nearly regular tetrahedron, slightly compressed along the S 4 axis.…”

“…The MoO 4 group has the shape of a nearly regular tetrahedron, slightly compressed along the S 4 axis. The oxygen sites have only trivial point symmetry and the crystal has an inversion center [15].…”