Structural, morphological and optical properties of cobalt-substituted MgMoO4 ceramics prepared by pyrolysis of citric acid precursors

Abstract

Magnesium-cobalt molybdate composites (Mg 1-x Co x MoO 4 : x = 0, 0.3, 0.4, 0.6, 0.8 and 1) were successfully synthesized through a facile sol-gel synthesis at low temperature, and characterized by thermogravimetric and differential thermal analysis (TG-DTA), X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FTIR), Raman spectroscopy, scanning electron microscopy (SEM), UV-Vis spectroscopy and colorimetric measurements using the CIE L*a*b* colour system. The surface specific area was calculated using the Brunauer-Emmett-Teller analysis in the adsorption/desorption isotherm. The examination of the X-ray diffractograms of the unground milled solid solutions of Mg 1-x Co x MoO 4 (0 ≤ x ≤ 1) presented a single continuous system related to monoclinic β-MgMoO 4 . The absorbance spectra of the Mg 1-x Co x MoO 4 pigments confirmed the insertion of cobalt in the β-MgMoO 4 matrix. The CIE-L*a*b* colour coordinates indicated that the intense purple colour was obtained for x = 0.6.

Purple nanometrics pigments based on cobalt-doped manganese molybdate: Synthesis, characterization, structural, thermal, optical, colorimetric and chemical properties

“…The relatively high value of this parameter might encourage the use of the composition x= 0.6 as a pigment in ceramic staining. This result was compatible with that obtained in the case of the Mg 1-x Co x MoO 4 system (0 ≤x≤ 1) [12].…”

“…The bands located at 754 and 760 cm -1 are characteristic of the tetrahedral [MoO 4 ] group, and their presence justifies the existence of the tetrahedral coordination of Mo [29,30]. The band located at 856 cm -1 is associated with the vibration mode of the Mo-O band [32], those located at 499 and 480 cm -1 are specific to the vibrations of Co-O-Mo bands [12,32].…”

“…As these two polymorphic varieties are of different colors (green and ocher, respectively), considering the use of this material as an indicator of temperature or pressure is thus possible [6][7][8][9]. Recently, the work carried out in our laboratory by H. Lakhlifi et al [10][11][12] showed that the partial substitution of cation A in the matrix of A 1-x Co x MoO 4 (A=Zn and Mg) by the chromophoric element cobalt allows the synthesis of new colored materials. Indeed, Co 2+ ions can induce different colorations depending on the environment they occupy.…”

“…Indeed, Co 2+ ions can induce different colorations depending on the environment they occupy. For example, in the tetrahedral site, they are at the origin of a blue color [10], while in regular octahedral coordination, a pink color is observed, and a purple hue is obtained when the latter is deformed [12].…”

Electronic, magnetic, optical properties, and morphological characteristics of nanocrystalline based on zinc–cobalt molybdate prepared by soft chemistry route

“…For the ZnCoMo-0.6-600 sample, The most high-intensity bands observed at 915 and 878 cm −1 correspond to the Mo-O (ν 1 (Ag)) symmetric stretching vibration [52]. Those located at 831 and 787 cm -1 are assigned to O-Mo-O antisymmetric stretching vibrations modes [53]. The bands observed at 355 and 318 cm -1 were designated to the Mo-O-Co stretching vibrations [54,55].…”