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A Raman spectroscopic study of synthetic giniite

By Ray L. Frost, Rachael-Anne Wills and Wayde N. Martens


The mineral giniite has been synthesised and characterised by XRD, SEM and Raman and infrared spectroscopy. SEM images of the olive green giniite\ud display a very unusual image of pseudo-spheres with roughened surfaces of around 1 to 10 microns in size. The face to face contact of the spheres suggests that the spheres are colloidal and carry a surface charge. Raman spectroscopy proves\ud the (PO4)3- units are reduced in symmetry and in all probability more than one type of phosphate unit is found in the structure. Raman bands at 77 K are observed at 3380 and 3186 cm-1 with an additional sharp band at 3100 cm-1. The first two bands are assigned to water stretching vibrations and the latter to an OH stretching band. \ud Intense Raman bands observed at 396, 346 and 234 cm-1are attributed to the FeO stretching vibrations. The giniite phosphate units are characterised by two Raman bands at 1023 and 948 cm-1 assigned to symmetric stretching mode of the (PO4)3- units. A complex band is observed at 460.5 cm-1 with additional components at 486.8 and 445.7 cm-1 attributed to the ν2 bending modes suggesting a reduction of symmetry of the (PO4)3- units

Topics: giniite, synthesis, phosphate, kintoreite, segnitite, scanning electron microscopy, Raman spectroscopy
Publisher: Elsevier
Year: 2007
DOI identifier: 10.1016/j.saa.2006.02.018
OAI identifier: oai:eprints.qut.edu.au:5741

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