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Pressure-Induced Stabilization of Terbium(IV) in CsTb(CrO4)2 Characterized by X-ray Absorption Spectroscopy
Tyler W Hines1, Lucia Amidani2,3, Nicholas B Beck1
1Department of Chemistry and Nuclear Science & Engineering Center, Colorado School of Mines, Golden, Colorado 80401, United States.
Abstract:
Single crystals of CsTb(CrO4)2 and CsDy(CrO4)2, where the lanthanide metals are in the trivalent state under ambient conditions, have been investigated under high-pressure conditions on the gigapascal scale utilizing a diamond anvil cell. These compounds were characterized by single-crystal X-ray diffraction in addition to high-pressure solid-state UV-vis-NIR spectroscopy, Raman spectroscopy, and Tb L3-edge high-energy-resolution fluorescence-detected X-ray absorption near-edge structure (HERFD-XANES). The high-pressure UV-vis-NIR spectra reveal strong broadening of the metal-to-ligand charge transfer band to lower energies, associated with a visible color change from yellow to dark red/black. Clear evidence for the stabilization of Tb4+ under high pressure is provided by the appearance of a second edge feature characteristic of Tb4+, starting at 19.62 GPa in the high-pressure L3-edge HERFD-XANES at around 7528 eV. This represents the first example of Tb4+ being stabilized by high pressure and expands upon the limited chemistry of terbium in the tetravalent state.
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