Characterization of Iraq-luster painted pottery by XRF and XAFS analysis

Luster is one of the most interesting Islamic ceramic decorations. Their origins are known to be due to a nanostructured thin layer formed by metallic copper and silver nanocrystals. The chemical composition of the glazes and decorations of Iraq luster potteries stored in IDEMITSU museum of art were studied using XRF quantitative analysis and XRF imaging. Moreover, the local environment of copper and silver dispersed in the glaze were analyzed by means of XAFS analysis. The white glaze of Iraq luster pottery can be classified into alkali-lime glaze and alkali-lead-lime glaze according to their contents of PbO and SnO2. The present XRF analysis revealed that the almost all samples belong to alkali-lead-lime glaze. In addition, it is found from XRF imaging that different copper/silver ratios affect the color of decorations. Cu K-edge and Ag K-edge XAFS spectra of these shards were measured to reveal the chemical state of copper and silver. Presence of metallic copper is found in the red luster. In olive green and brown luster, copper is almost present in the Cu (I) state. Also, in dark brown luster, both Cu (I) and Cu (II) states are found, while, silver always exists in the metallic form independent of the color. (author)