Single-crystal x-ray investigations on strontium feldspar

Abstract

AuszugMit Hilfe von Einkristall-Methoden wurden an synthetischen Kristallen von Strontium-Feldspat Überstrukturreflexe vom Typ b beobachtet und damit die vermutete Gitterkonstante von 14 Ä bestätigt. Als Raumgruppe wurde 12/c bestimmt, wodurch die Annahme gestützt wird, daß der Strontium-Feldspat isostrukturell mit Celsian ist. Ein Karlsbader Zwilling wurde röntgenographisch nachgewiesen. AbstractThe crystal structure peculiarities of strontium feldspar were confirmed experimentally by a single-crystal x-ray analysis on synthetic crystals. Type b superlattice reflections were found and the length of the c parameter (14 Ä) was confirmed. The space group is I 2/c and this affirms the supposition that strontium feldspar is isostructural with celsian. A crystal twinned according to the Carlsbad law was found and examined. The complete diadochic substitution Ca-Sr and Sr-Ba, found in the aluminosilicates with formula (X,Y) [AI2S12O8] and described in several recentarticles (BRUNO and GAZZONI, 1968; BRUNO and GAZ- ZONI, 1969; NAGER, HOFFMANN and NISSEN, 1969; NAGER, BAMBATJERand HOFFMANN, 1970), made us wonder whether also the monoclinic phase SrAl2Si20s would be approximately isostructural with the calcium and barium feldspars. For the monoclinic compounds BaAl2Si20e and SrAl 2 Si 2 08, in particular, the closeness between unit-cell parameters and the strict resemblance of frequencies and intensities in the relative infrared spectra make it very likely that they are isostructural. It had still to be experimentally proved, however, that also strontium feldspar has c ~ 14 Ä. Such a value is demanded by Brought to you by | New York University Bobst Library Technical Service Authenticated Download Date | 7/15/15 10:04 PM

A Single‐Phased Sr1−y‐3x/2Al2Si2O8: xCe3+, yMn2+ with Efficient Energy Transfer as a Potential Phosphor for White‐Light‐Emitting Diodes

“…Moreover, as the bond lengths of the large cation to oxygen vary, the coordination of these large cations (and thus the substituted ions) can also vary depending on where cation selects the coordination sphere. According to Bruno and Gazzoni, the more abundant naturally occurring stable monoclinic form of SrAl 2 Si 2 O 8 is called celsian (S.G: I 2/ c ) and the less metastable form is called paracelsian (S.G: P 21/ a ). These include a naturally occurring monoclinic form similar to paracelsian that is called slawsonite (S.G: P 21/ a ), a synthetic monoclinic form (S.G: I2/c) to celsian, and a second synthetic form (S.G: P 6/ mmm ) similar to hexacelsian.…”

Ferroelastic phase transition in SrAl2Si2O8 feldspar at elevated pressure

“…Bragg reflections were measured by fitting Gaussian curves to the corrected background diffracted intensity. The patterns were indexed according to the cell reported by Bruno and Gazzoni (1970). The NaC1 peaks were measured separately from the feldspar peaks and the cell parameters of each phase calculated by a least squares refinement.…”

Synthesis, X-ray crystallography and infrared absorption spectroscopy of EuAl2Si2O8.

“…This value is low relative to the calculated value, perhaps, because of the contamination of glassy parts in the sample. BRUNO and GAZZONI, 1970). Sr(C): Sr0.84 Na0 .03A11.69` 12.2908.…”