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

Abstract

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