Wolfgang Schöfberger,
"Insight into Framework Destruction in Ultramarine Pigments"
, in Inorganic Chemistry, Vol. 45, American Chemical Society Publications, Seite(n) 1270-1276, 2006, ISSN: 1520-510X
Original Titel:
Insight into Framework Destruction in Ultramarine Pigments
Sprache des Titels:
Englisch
Original Kurzfassung:
We report key evidence on the framework destruction in ultramarine pigments upon color fading. Experiments on
faded pigments in a fresco painting environment reveal that the paramagnetic chromophores are set free via
sodalite framework destruction and are subsequently degraded. Fading in acidic media produces similar results,
although a larger number of â-cages appear to be destroyed, and H2S is released. The findings are further supported
by studies on natural and synthetic ultramarine pigments of various shades via solid-state resonance-Raman
spectroscopy, colorimentry, and solid-state 29Si and 27Al NMR spectroscopy. NMR parameters are shown to correlate
well with the intensities of Raman signals corresponding to the S3-chromophores. A further correlation is established
between the colorimetric parameters, L* (lightness) and C* (chroma), and the paramagnetic shift and paramagnetic
linebroadening in NMR spectra for both 27Al and 29Si.