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Synthesis of hafnium tungstate by a CO 2 laser and its microstructure and Raman spectroscopic study
Author(s) -
Liang E. J.,
Wang J. P.,
Xu E. M.,
Du Z. Y.,
Chao M. J.
Publication year - 2008
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.1929
Subject(s) - raman spectroscopy , orthorhombic crystal system , tungstate , materials science , scanning electron microscope , microstructure , laser , laser power scaling , analytical chemistry (journal) , diffraction , crystal structure , crystallography , optics , chemistry , composite material , metallurgy , physics , chromatography
Densely packed hafnium tungstate blocks were synthesized by rapid solidification with a CO 2 laser. It is shown that the optimum synthesis conditions for HfW 2 O 8 are around 700 W laser power and 1 mm/s scan speed. Scanning electron microscopy (SEM) observation shows that the blocks consist of oriented nano‐threads/rods that grew horizontally on the surface region and vertically in the interior. The orientations of the nanostructures are governed by the heat transfer directions on the surface and in the interior. Raman spectroscopic and X‐ray diffraction studies show that the samples solidified in the cubic structure with minor contents of the orthorhombic phase. This is explained by a compressive stress induced during the rapid solidification process due to a sudden drop of temperature of the molten pool to the ambient. The stress is estimated to be about 0.6 GPa by comparison with high‐pressure Raman study. Some specific Raman bands appear in the samples synthesized with the laser synthetic route but not in the sample by solid‐state reaction. Copyright © 2008 John Wiley & Sons, Ltd.