%0 Journal Article %1 WOS:000246753100010 %A Paraguassu, W %A Maczka, M %A Filho, A G Souza %A Freire, P T C %A Melo, F E A %A Filho, J Mendes %C RADARWEG 29, 1043 NX AMSTERDAM, NETHERLANDS %D 2007 %I ELSEVIER %J VIBRATIONAL SPECTROSCOPY %K Raman amorphization; calculation} dynamics expansion; induced lattice pressure scattering; thermal {negative %N 1 %P 69-77 %R 10.1016/j.vibspec.2006.08.006 %T A comparative study of negative thermal expansion materials Sc-2(MoO4)(3) and Al-2(WO4)(3) crystals %V 44 %X Polarized Raman spectra and polycrystalline spectra of isomorphous Sc-2(MoO4)(3) and Al-2(WO4)(3) crystals have been measured at room temperature and ambient pressure. Some Raman spectra Of Sc-2(MoO4)(3) were taken at different values of pressures in the range of 0.0-3.0 GPa. Lattice dynamics calculations have been performed on the orthorhombic phase (ambient phase) of these materials using a rigid ion model in order to calculate the phonon frequencies at the Brillouin zone Center (k = 0). The calculated results fit qualitatively well the Raman spectra observed in these materials at room temperature and ambient pressure, and allowed us to establish their Raman signature. A higher coupling among the modes of the Al-2(WO4)(3) material compared with Sc-2(MoO4)(3) material was observed. The pressure dependent studies revealed that the 362 and 433 cm(-1) modes of Sc-2(MoO4)(3) and Al-2(WO4)(3), respectively, exhibit unusually high awlaP values. The presence of these unstable modes in both materials is probably related to the mechanism of the phase transition from the monoclinic high-pressure phase to the unknown phase of lower symmetry. (c) 2006 Elsevier B.V. All rights reserved.

@article{WOS:000246753100010, abstract = {Polarized Raman spectra and polycrystalline spectra of isomorphous Sc-2(MoO4)(3) and Al-2(WO4)(3) crystals have been measured at room temperature and ambient pressure. Some Raman spectra Of Sc-2(MoO4)(3) were taken at different values of pressures in the range of 0.0-3.0 GPa. Lattice dynamics calculations have been performed on the orthorhombic phase (ambient phase) of these materials using a rigid ion model in order to calculate the phonon frequencies at the Brillouin zone Center (k = 0). The calculated results fit qualitatively well the Raman spectra observed in these materials at room temperature and ambient pressure, and allowed us to establish their Raman signature. A higher coupling among the modes of the Al-2(WO4)(3) material compared with Sc-2(MoO4)(3) material was observed. The pressure dependent studies revealed that the 362 and 433 cm(-1) modes of Sc-2(MoO4)(3) and Al-2(WO4)(3), respectively, exhibit unusually high awlaP values. The presence of these unstable modes in both materials is probably related to the mechanism of the phase transition from the monoclinic high-pressure phase to the unknown phase of lower symmetry. (c) 2006 Elsevier B.V. All rights reserved.}, added-at = {2022-05-23T20:00:14.000+0200}, address = {RADARWEG 29, 1043 NX AMSTERDAM, NETHERLANDS}, author = {Paraguassu, W and Maczka, M and Filho, A G Souza and Freire, P T C and Melo, F E A and Filho, J Mendes}, biburl = {https://www.bibsonomy.org/bibtex/23422e7a8c3250212c84c53c12b137abc/ppgfis_ufc_br}, doi = {10.1016/j.vibspec.2006.08.006}, interhash = {5d123d5999c180d0ca5629179485ef41}, intrahash = {3422e7a8c3250212c84c53c12b137abc}, issn = {0924-2031}, journal = {VIBRATIONAL SPECTROSCOPY}, keywords = {Raman amorphization; calculation} dynamics expansion; induced lattice pressure scattering; thermal {negative}, number = 1, pages = {69-77}, publisher = {ELSEVIER}, pubstate = {published}, timestamp = {2022-05-23T20:00:14.000+0200}, title = {A comparative study of negative thermal expansion materials Sc-2(MoO4)(3) and Al-2(WO4)(3) crystals}, tppubtype = {article}, volume = 44, year = 2007 }