title: [Raman and infrared spectra of non-stoichiometry uranium oxides].
abstract: Both of Raman and infrared spectra of seven non-stoichiometry and threestoichiometry uranium oxides, including UO2, U3O7 and UO(2+x) (0<x<0.66), are presented and discussed. The spectra of UO(2+x) in the stoichiometry range, U3O7 to U3O8, were first obtained and reported. Three typical peaks were observed at 445, 578 and 1150 cm(-1) in the Raman spectrum of uranium dioxide. The intensities of the peaks at 578 and 1151 cm(-1) decrease quickly with increasing x value of UO(2+x), and while x=0.19, the two peaks disappear. Such peaks can therefore be considered as a fin-gerprint of the quasi-perfect UO2 fluorite structure. The peak at 445 cm(-1) tends to weaken, broaden and shift to higher wavenumber in more oxidised samples. When x=0.32, this peak is shifted to the 459 cm(-1) and a weak peak at about 630 cm(-1) appears. The two new peaks are typical of the tetragonal U3O7. While x> or =0.39, the peak at 459 cm(-1) further splits into separate components. Two peaks at 235 and 754 cm(-1) appear for UO(2.39) and are visible with increased intensity as the oxygen-uranium ratio is increased. And the Raman spectra of UO(2+x) are gradually close to U3O8 in the alpha-phase, which has an orthorhombic unit cell. But several strongest features of the alpha-U3O8 specturm at 333, 397, 483 and 805 cm(-1) are still not outstanding even in UO(2.60). The main feature of the UO2 infrared spectrum shows a very broad and strong adsorption band at 400-570 cm(-1) and another feature is a weak adsorption peak at about 700 cm(-1). The 400-570 cm(-1) band undergoes a progressive splitting into two new peaks at approximately 421 and approximately 515 cm(-1) through increasing incorporation of oxygen into UO2. The weak peak at about 700 cm(-1) disappears and a new weak peak appears at about 645 cm(-1). The three new peaks are the infrared absorption features of U3O7. An absorption peak at 744 cm(-1) which is the strongest feature of alpha-U3O8 infrared spectrum appears for UO(2.39) and is visible with increased intensity in more oxidised samples. The peak at about 645 cm(-1) still exists and 515 cm(-1) peak has no further splitting into two new peaks at 485 and 535 cm(-1) which also are the infrared absorption features of U3O8 in UO(2.60). This indicates that UO(2.60) is still in the transition period between tetragonal and orthorhombic phase of uranium oxide. A sequence of phase transitions occurs through increasing x value of UO(2+x) with different Raman and infrared features. It is easy to identify different uranium oxides by comparing of relative intensities and locations of their characteristic peaks.
authors.forename: Jun-Bo
authors.initials: JB
authors.lastname: Lü
authors.forename: Gan
authors.initials: G
authors.lastname: Li
authors.forename: Shu-Lan
authors.initials: SL
authors.lastname: Guo