On the sol-gel preparation of different tungstates and molybdates
|Original title:||On the sol-gel preparation of different tungstates and molybdates|
|Authors:||Arturas Zalga, Zdeněk Moravec, Jiří Pinkas, Aivaras Kareiva|
|Type:||Article in Periodical|
|Keywords:||Sol-gel synthesis; Precursors; TG DSC; Tungstates; Molybdates|
The preparation and characterization of the M`-M``-O nitrate-tartrate (M0 = Ca, Ba, Gd and M0 = W, Mo) precursor gels synthesized by simple, inexpensive, and environmentally benign aqueous sol-gel method is reported. The obtained gels were studied by thermal (TG/DSC) analysis. TG/DSC measurements revealed the possible decomposition pathway of synthesized M`-M``-O-nitrate-tartrate gels. For the synthesis of different metal tungstates and molybdates, the precursor gels were calcined at different temperatures (650, 800, and 900 degC). According to the X-ray diffraction (XRD) analysis data, the crystalline compounds CaMo 1-x W x O 4 doped with Ce3+ ions, BaMo 1-x W x O 4 doped with Eu 3+ ions and Gd 2 Mo 3 O 12 were obtained from nitrate-tartrate gels annealed at 650-900 degC temperatures. The XRD data confirmed that the fully crystalline single-phase powellite, scheelite, or Gd 2 (MoO 4 ) 3 structures were formed already at 650 degC. Therefore, the suggested sol-gel method based on the complexation of metal ions with tartaric acid is suitable for the preparation of mixed tungstates-molybdates at relatively low temperature in comparison with solid-state synthesis.