Structural, vibrational and thermal expansion properties of Sc2W4O15

Abstract

A novel oxide material with the formula of Sc₂W₄O₁₅ and orthorhombic symmetry is synthesized by solid state reactions and its structure, composition, vibrational properties and thermal expansion are investigated and identified by temperature-dependent X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), X-ray photoelectron spectrometry (XPS) and dilatometry. It is shown that the oxide material with an orthorhombic symmetry shows a similar structure to that of Sc₂W₃O₁₂, but with W partially occupying the position of Sc, leading to not only the corner-sharing ScO₆–WO₄ connections but also the corner-sharing WO₆–WO₄ connections. Raman spectroscopic studies show that compared to Sc₂W₃O₁₂, the FWHMs of most Raman modes in Sc₂W₄O₁₅ increase due to the occupation of W⁶⁺ in the Sc³⁺ position. Besides, the W–O bonds in Sc₂W₄O₁₅ are slightly harder than those in Sc₂W₃O₁₂. An intrinsic thermal contraction in a wide range of temperatures (93–572 K) is demonstrated, which is attributed to the librational and translational vibrations of the corner-sharing polyhedra as well as the transverse vibrations of the bridging O atoms in the Sc–O–W and W–O–W linkages.