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Investigation of structural transition in molybdates CuMo1-xWxO4 prepared by polymeric precursor method

Benchikhi Mohamed (Université Hassan II Casablanca, Laboratoire de Physico-Chimie des Matériaux Inorganiques, Morocco + Université Paul-Sabatier, Institut Carnot CIRIMAT, UMR CNRS-UPS-INP, CNRS, Toulouse, France)
El Ouatib Rachida (Université Hassan II Casablanca, Laboratoire de Physico-Chimie des Matériaux Inorganiques, Morocco)
Guillemet-Fritsch Sophie (Université Paul-Sabatier, Institut Carnot CIRIMAT, UMR CNRS-UPS-INP, CNRS, Toulouse, France)
Er-Rakho Lahcen (Université Hassan II Casablanca, Laboratoire de Physico-Chimie des Matériaux Inorganiques, Morocco)
Durand Bernard (Université Paul-Sabatier, Institut Carnot CIRIMAT, UMR CNRS-UPS-INP, CNRS, Toulouse, France)

Solid solutions (CuMo1-xWxO4 where 0 ≤ x ≤ 0.12) were synthesized by using a polymeric precursor method. The crystallization process of the polymeric precursors was investigated using TG-DTA, FTIR and XRD techniques. Crystallization of the CuMo1-xWxO4 powders was detected at 300°C, and entirely completed at 420°C. XRD patterns revealed that the polymorphic variety was dependent upon the tungsten content. For x ≤ 0.075, the solid solutions were isostructural to α-CuMoO4 whereas, for 0.075 < x ≤ 0.12, they were isostructural to γ-CuMoO4. The obtained homogeneous powders are constituted of relatively spherical grains with sizes in the range 0.5-2.0 μm. The phase transition of the as-synthesized CuMo1-xWxO4 powders was investigated by X-ray diffraction at elevated temperature and dilatometry. The temperature of the structural transition γ → α during heating was dependent upon the tungsten content.

Keywords: thermochromism, sol-gel processes, thermal analysis, structural characterization