A Raman spectroscopic study of high-uranium zircon from the Chernobyl "lava"
A Raman spectroscopic study of high-uranium zircon from the Chernobyl "lava"
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DOI：
10.1127/0935-1221/2005/0017-0883
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发表时间：
2005-11-01
影响因子：
2.1
通讯作者：
Pöml, P
中科院分区：
文献类型：
--
作者：
Geisler, T;Burakov, BE;Pöml, P
我们利用共聚焦拉曼光谱、电子探针和背散射电子成像技术，研究了1986年切尔诺贝利核电站事故中熔体结晶而成的技术成因的高铀锆石。拉曼和电子探针测量之间的相关性允许研究作为强分带锆石晶体U含量的函数的模式行为。晶体中USiO4的含量在0.6~11.6摩尔之间。%，分别对应0.8和15.8wt.%的UO2。Nu(1)(SiO4)对称和Nu(1)(SiO4)反对称伸缩模式的频率每摩尔分别下降0.67(3)和0.75(3)cm(-1)。%USiO4，这是随着U含量的增加，Si-O键长增加的结果。晶格模向低频方向移动，而Nu(2)(SiO4)和Nu(4)(SiO4)内弯曲模没有或仅向低频(<；0.12 cm(-1))每摩尔有微小的移动。%U)。随着U含量的增加，只有202 cm-1附近最低能带(E-g)的频率略有增加，这是意想不到的，表明阳离子-(SiO4)(4-)势、电子轨道和/或阳离子半径对这种模式有很大的影响。反映局域变形范围(即微观应变)的谱线展宽对于晶格模最为明显，这与两种阳离子的大尺寸差异相一致。我们发现，涉及SiO4四面体运动和a(B)面内阳离子的E-g晶格模的谱线宽度随U浓度的增加而显著大于Bg晶格模，涉及晶格沿c轴的振动。这表明a(B)面上的微观应变明显大于c轴上的应变，这可以用锆石的结构性质来解释。
We have studied technogenic, high-uranium zircon, which crystallised from melt formed during the accident at the Chernobyl Nuclear Power Plant in 1986, by confocal Raman spectroscopy, electron microprobe, and backscattered electron imaging. The correlation between Raman and electron microprobe measurements allowed studying mode behaviour as a function of U content of the strongly zoned zircon crystals. The USiO4 content in the crystals ranges between 0.6 and 11.6 mol. %, corresponding to 0.8 and 15.8 wt. % UO2 respectively. The frequency of the nu(1)(SiO4) symmetrical and nu(1)(SiO4) anti-symmetrical stretching mode decreases by 0.67(3) and 0.75(3) cm(-1) per mol. % USiO4, respectively, which is a result of an increasing Si-O bond length with increasing U content. The lattice modes show a comparable shift to lower frequencies, whereas the internal nu(2)(SiO4) and nu(4)(SiO4) bending modes exhibit no or only a small shift to lower frequencies (< 0.12 cm(-1) per mol. % U). Only the frequency of the lowest energy band (E-g) near 202 cm-1 increases slightly with increasing U content, which is unexpected and indicates that the cation-(SiO4)(4-) potentials, the electron orbitals, and/or the cation radius have a strong effect on this mode. The line broadening, reflecting the range of local distortions (i.e., microscopic strain), is most pronounced for the lattice modes, in agreement with the large size difference of both cations. We found that the E-g lattice modes, involving the movement of the SiO4 tetrahedron and the cation within the a(b) plane, show significantly larger line broadening with increasing U concentration than the B g modes, involving lattice vibrations along the c axis. This suggests that the microscopic strain is significant larger in the a(b) plane than along the c axis, which can be explained by the structural properties of zircon.