Effect of Water Species on the Phonon Modes in Orthorhombic Y2(MoO4)3 Revealed by Raman Spectroscopy
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- 作者：Erjun Liang ; Haolei Huo ; Junping Wang ; Mingju Chao
- 刊名：Journal of Physical Chemistry C
- 出版年：2008
- 出版时间：April 24, 2008
- 年：2008
- 卷：112
- 期：16
- 页码：6577 - 6581
- 全文大小：267K
- 年卷期：v.112,no.16(April 24, 2008)
- ISSN：1932-7455
文摘
Negative thermal expansion material of yttrium molybdate has been synthesized by rapid solidification witha CO2 laser. It crystallized in the orthorhombic phase with unique microstructures consisting of nanoparticlesor nanodendrites with grain sizes around 20-30 nm. Raman spectroscopic and XRD analyses reveal that thepresence of water species hinders not only the rocking motion but every type of motion of the corner sharedpolyhedra. Because of the presence of water species, degeneracy of the Raman bands happens for symmetricstretching, asymmetric stretching, and the bending modes, and the lattice, translational, and librational modescannot be observed. The release of water species below 403 K (388 K for the newly prepared sample or 383K in the second temperature cycle) has little whereas that above this temperature has great effect on thestretching and bending vibrations and also the librational and translational modes. This indicates that thewater species which are released within the first step do not interact with the MoO4 tetrahedra in the Y2Mo3O12 framework while those released in the second step have a direct interaction. It is suggested that thetranslational and librational motions are closely coupled with stretching and bending vibrations. They togethergive rise to the negative thermal expansion.