Revisiting the five-decade-old structure of the Fe2WO6 powder with incommensurate modulations

Iron tungstate, Fe2WO6, is a promising photocatalytic, thermoelectric and electrochemically active material for energy storage devices. However, its structure is poorly described in the literature reporting on these applications. For the first time, we solved the crystal structure of its high temperature form using powder X-ray diffraction and the incommensurately modulated structural model. The structure adopts a (3 + 1)-dimensional Pbcn(0 beta 0)000 superspace group with the cell parameters a = 4.57964(7) angstrom, b = 5.58662(8) angstrom, and c = 4.96920(7) angstrom and the modulation vector q = 0.6687(4) b*, close to the commensurate case q = 2/3 b*. The first-order satellite reflections visible in the powder diffraction patterns show, compared to the main reflections, a substantial broadening of the diffraction lines, caused by the small size of the ordered domains. This broadening has been successfully described using a line-broadening model, designed for incommensurately modulated structures, and confirms the incommensurate structural description. Such findings can be of great help to further understand the reported physical and electrochemical properties.

Automated summary

Iron tungstate is a promising material for energy storage devices, with its high temperature form exhibiting an incommensurately modulated crystal structure. The broadening of diffraction lines in powder patterns suggests small ordered domains within the structure. These findings can aid in understanding the reported physical and electrochemical properties.