Contribution
Synthesis, XRD and FTIR studies of strontium richterites
Della Ventura, Giancarlo; Robert, Jean-Louis
European Journal of Mineralogy Volume 2 Number 2 (1990), p. 171 - 176
18 références bibliographiques
publié: Apr 5, 1990
manuscrit accepté: Nov 28, 1989
manuscrit reçu: Jul 27, 1989
DOI: 10.1127/ejm/2/2/0171
Abstract
Abstract An infrared investigation of hydrothermally prepared Sr-substituted Na and K richterites is presented. X-ray powder data show a notable increase of the a, b, and β parameters due to the larger ionic radius of eight-fold coordinated Sr2+ with respect to Ca2+. The infrared spectra rule out the presence of Sr2+ in the A-site, thus demonstrating that strontium should be allotted to the M(4) site. In the spectrum of Na-Sr-richterite, the major-intensity band is split into two components, at 3730 and 3725 cm-1 , and a tremolite-type band is observed at 3670 cm-1 due to OH dipoles pointing towards apparently vacant A-sites. The potassic strontium end-member exhibits a single sharp band at 3735 cm-1 in the region of OH-stretching wavenumbers. These observations are discussed in terms of local polyhedral geometry. The usefulness of infrared spectroscopy is stressed for defining local structural features, at least in chemically simple amphiboles.
Mots-clefs
Sr-richterites • FTIR absorption spectrometry • synthetic amphibole • order-disorder