Effects of W⁶⁺ occupying Sc³⁺ on the structure, vibration, and thermal expansion properties of scandium tungstate*

Abstract

We experimentally investigate effects of W6+ occupying the sites of Sc3+ in the unit cell of Sc2W3O12 (Sc8W12O48) on the structure, vibration and thermal expansion. The composition and structure of the doped sample (Sc6W2)W12O48 ± δ (with two W6+ occupying two sites of Sc3+ in the unit cell of Sc8W12O48) are analyzed and identified by combining the x-ray photoelectron spectroscopy and the synchronous x-ray diffraction with first-principles calculations based on density functional theory. Results show that the crystal with even W6+ occupying even Sc3+ in the unit cell is stable and maintains the orthorhombic structure at room temperature. The structure of the doped sample is similar to that of Sc2W3O12, and with even W occupying even positions of Sc in the unit cell and constituting the WO6 octahedra. Raman analyses show that the doped sample possesses stronger W–O bonds and wider Raman linewidths than those of Sc2W3O12. The sample doped with W also exhibits intrinsic negative thermal expansion in the measured range of 150 K–650 K.

Simultaneously tuning the luminescent color and realizing an optical temperature sensor by negative thermal expansion in Sc2(WO4)3:Tb/Eu phosphors

“…The mode below 200 cm −1 is deemed as the translations and liberations (T′(WO 4 ), L(WO 4 )) of the WO 4 tetrahedra. 31 To further understand the shift in diffraction peaks with varying tempera-ture, the two-dimensional topographical mappings of temperature-dependent in situ enlarged XRD patterns for the (020) and (202) peaks are shown in Fig. 1c and d 32,33 The in situ XRD patterns of SWO:25%Tb/3%Eu were subjected to Rietveld refinement using the structural model of Sc 2 (WO 4 ) 3 .…”