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

Lead tin yellow type I (Pb2SnO4) and type II (PbSn1–xSixO3) 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.