Synthesis of molybdates Zn1-xCoxMoO4 (0 ≤ x ≤ 1), by decomposition of the precursors developed by the glycine-nitrate process (GNP), and their characterization

Nanocrystals of zinc-cobalt molybdate (Zn1-xCoxMoO4) were prepared by the glycine-nitrate process (GNP) route with a glycine/nitrate ratio of 2:3 and compared to the solid state synthesis. The obtained powders were characterized by thermal analysis (TGA-TDA), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. The morphology was examined by scanning electron microscopy (SEM) and Brunauer–Emmett–Teller (BET). The particle size was determined by transmission electron microscopies (TEM). UV–Visible spectroscopy and CIE L*a*b* colorimetric parameters have been used for the colour characterisation and measurement. The compounds obtained present two single-phased domains regardless of the synthesis method. The first domain of blue colour corresponding to a level of cobalt x such as: 0 = x ≤ 0.3, isostructural with α-ZnMoO4 of triclinic symmetry and the second domain of green colour, for cobalt x levels such as: 0.45 = x ≤ 1 isostructural with α-CoMoO4 of monoclinic structure. The Zn0.7Co0.3MoO4 powders obtained at 700 °C by GNP route and synthesized in acidic environment were formed of particles of quasi-spherical morphology, with average size of crystallites estimated between 80 - 140 nm