Modified Naples yellow in Renaissance majolica: study of Pb-Sb-Zn and Pb-Sb-Fe ternary pyroantimonates by X-ray absorption spectroscopy

X-Ray absorption spectroscopy investigations combined with ab initio structural simulations of ternary forms (Pb-Sb-Zn and Pb-Sb-Fe) of the pigment Naples yellow (Pb2Sb2O7) allowed to achieve a detailed insight into the incorporation route of Zn and Fe ions inside the pigment lattice. The study of newly synthesised yellow pyroantimonates provided direct evidence that Zn and Fe ions enter the pyrochlore octahedral sites replacing Sb ions. Experimental results were discussed considering, also, the information provided by Raman spectroscopy used in this study as a sensitive probe of the pyrochlore lattice distortions in modified yellow pyroantimonates. Finally, by exploiting the non-invasiveness of the X-ray absorption spectroscopy technique, the same structural arrangement has been unambiguously observed for Zn cations in a modified Naples yellow pigment of a Renaissance ceramic shard.