Vibrational spectroscopy of selected natural uranyl vanadates

Abstract

Dermot (2005) range and are assigned to the doubly degenerate ν 2 modes of the (UO 2 ) 2+ units. The study of the vibrational spectroscopy of uranyl vanadates is complicated by the overlap of bands from the (VO 3 ) and (UO 2 ) 2+ units. Raman spectroscopy has proven most useful in assigning bands to these two units since Raman bands are sharp and well separated as compared with infrared bands. The uranyl vanadate minerals are often found as crystals on a host matrix and Raman spectroscopy enables their in-situ characterisation without sample preparation.

Framework Polymorphism and Modular Crystal Structures of Uranyl Vanadates of Divalent Cations: Synthesis and Characterization of M(UO2)(V2O7) (M = Ca, Sr) and Sr3(UO2)(V2O7)2

“…For all three compounds, the bands between 247 and 285 cm –1 are assigned to bending vibrations of (UO 2 ) 2+ uranyl ions . The bands from 852 to 914 are assigned to antisymmetric stretching vibrations of (UO 2 ) 2+ uranyl ions;, however, other studies suggests these bands are due to stretching vibrations of VO 3 , …”

“…The Raman spectra of all three compounds are similar due to the similarities in their structures composed of UO 7 pentagonal bipyramids and V 2 O 7 pyrovanadate groups. The intense bands observed at 773, 787, and 785 cm –1 are assigned to symmetric stretching vibrations of (UO 2 ) 2+ uranyl ions for Ca(UO 2 )V 2 O 7 , Sr(UO 2 )V 2 O 7 , and Sr 3 (UO 2 )(V 2 O 7 ) 2 respectively , . For all three compounds, the bands between 247 and 285 cm –1 are assigned to bending vibrations of (UO 2 ) 2+ uranyl ions .…”

“…The intense bands observed at 773, 787, and 785 cm –1 are assigned to symmetric stretching vibrations of (UO 2 ) 2+ uranyl ions for Ca(UO 2 )V 2 O 7 , Sr(UO 2 )V 2 O 7 , and Sr 3 (UO 2 )(V 2 O 7 ) 2 respectively , . For all three compounds, the bands between 247 and 285 cm –1 are assigned to bending vibrations of (UO 2 ) 2+ uranyl ions . The bands from 852 to 914 are assigned to antisymmetric stretching vibrations of (UO 2 ) 2+ uranyl ions;, however, other studies suggests these bands are due to stretching vibrations of VO 3 , …”

“…The vibrations from the equatorial U–O bonds are in the range from 450 to 552 cm –1 . [41a] The bands from 335 to 400, 697 to 755, and 922 to 961 are assigned to bending vibrations of VO 3 , antisymmetric stretching of V–O–V and VO 3 , and symmetric stretching mode of VO 3 respectively 41b] Detailed assignments of all the peaks are summarized in Table S1 (Supporting Information).…”

Electrical properties and complex impedance analysis of K2ZnV2O7

“…Electrical impedances were recorded in the frequency ranging from 200 Hz to 1 MHz in a TEGAM 3550 ALF automatic bridge monitored by a microcomputer and a temperature controller. Measurements were carried out in the temperature range from 514 to 723 K. bands by comparison with similar compounds [8,9]. V 2 O 7 -4 frequencies are assigned on the basis of characteristic vibrations of V-O-V bridge and VO 3 groups.…”