Synthesis, structural characterisation and Raman spectroscopy of the inorganic pigments lead tin yellow types I and II and lead antimonate yellow: their identification on medieval paintings and manuscripts

Abstract

Lead tin yellow type I (Pb₂SnO₄) and type II (PbSn_1–xSi_xO₃) have each been prepared in a high-temperature furnace, and the preparative conditions defined. The crystal structure of type II has been refined from powder X-ray diffraction data and indicates that the Sn and Si atoms are randomly distributed over the same type of site with Sn/Si ratio ≈ 3/1 (i.e., x≈¼). The Raman spectra of each form and also that of lead antimonate yellow (Pb₂Sb₂O₇) have been obtained. Raman microscopy is shown to be an effective technique whereby these inorganic yellow pigments as minute (≈ 1 µm) grains may be identified on medieval manuscripts and paintings.