Fine structures and their impacts on the characteristic Raman spectra of molten binary alkali tungstates

Abstract

Comparing with the crystalline tungstate compounds, little work has been carried out and reported on the relation among the microstructure, W–O bond lengths, and characteristic Raman‐active vibration wavenumber of the molten tungstates, which allows us to diagnose and determine the structure of unknown clusters existing in and further predict the physicochemical properties of molten binary alkali tungstates. Raman spectra of an ensemble of eight model clusters were simulated in the present work by density functional theory (DFT) to establish the effect of the fine structures and W–Onb (non‐bridging oxygen) bond lengths of W–O complexes on the characteristic wavenumber of W–Onb Raman‐active vibration modes of the molten tungstates. Results show that the characteristic wavenumbers of the symmetric stretching vibration modes of W–Onb bonds increase almost linearly with the decreasing bond length. The characteristic wavenumbers of W–Onb symmetric stretching vibration modes generally follow [WO4]2− > [WO5]4− > [WO6]6− present in the melt simultaneously. The characteristic wavenumbers were also found to increase with the number of bridging oxygen for the same W–O complex. In situ Raman spectra of molten A2WnO3n + 1 (A = Li, Na, K; n = 1, 2, 3) were then measured in order to verify the correlation observed among the microstructure, W–O bond lengths, and characteristic Raman‐active vibration mode wavenumbers. The correlation was successfully applied to deconvolute the in situ Raman spectrum of the molten Na2W3O10.

Synthesis Attempt and Structural Studies of Novel A2CeWO6 Double Perovskites (A2+ = Ba, Ca) in and outside of Ambient Conditions

“…Both problematically fitting Raman spectra predicted in Figure a; for CCWO, R 3 c seems to meet the satisfactory, lesser number of Raman 7A 1 +14E phonons as shown in Figure b. Crude experimental positioning with brief characterization was enlisted and scientifically supported − in Table . FTIR spectra have been proven to contribute less toward the whole discussion, so their literature-based interpretation − and commentary were moved to Supporting Information p S11 with Table S4.…”

Synthesis and Properties of the Ba2PrWO6 Double Perovskite

“…The former was recorded on a single-crystalline grain, hoping to minimize the peak widths. The deconvoluted peak positions, together with literature-based mode assignments, − are summarized in Table . As can be seen, the number of detected Raman peaks exceeds the 12 modes predicted by group theory for perfect I 2/ m (7A 1g + 5B g ) as well as R -3 (4A g + 4 1 E g + 4 2 E g ) SGs (for the total number of predicted phonon modes and their irreducible representations, see Table S3).…”