XAFS study of copper and silver nanoparticles in glazes of medieval middle-east lustreware (10th-13th century)

ABSTRACT It has recently been shown that lustre decoration of medieval and Renaissance pottery consists of silver and cop- per nanoparticles dispersed in the glassy matrix of the ceramic glaze. Here the findings of an X-ray absorption fine structure (XAFS) study on lustred glazes of shards belonging to 10th and 13rd century pottery from the National Museum of Iran are reported. Absorption spectra in the visible range have been also measured in order to investigate the relations between colour and glaze composition. Gold colour is mainly due to Ag nanoparticles, though Ag + ,Cu + and Cu 2 + ions can be also dis- persed within the glassy matrix, with different ratios. Red colour is mainly due to Cu nanoparticles, although some Ag nanopar- ticles, Ag + and Cu + ions can be present. The achievement of metallic Cu and the absence of Cu 2 + indicate a higher reduc- tion of copper in red lustre. These findings are in substantial agreement with previous results on Italian Renaissance pottery. In spite of the large heterogeneity of cases, the presence of cop- per and silver ions in the glaze confirms that lustre formation is mediated by a copper- and silver-alkali ion exchange, followed by nucleation and growth of metal nanoparticles.