Antimony oxides: the pyrochlore-type structure revisited

Antimony oxides display a variety of structural arrangements with different stoichiometries resulting from two stable speciations for Sb ions. They commonly occur as minerals with well known crystal structure, but there are still questions regarding stibiconite a very rare yellow mineral with pyrochloretype structure and approximate formula Sb3O6(OH) [1]. Great interest has been focused on synthetics because of antimony speciation in relation to color and crystal structure [2], and important ion exchange properties of Sbpyrochlores were recently pointed out [3]. When studying yellow glazes from majolicatype tiles using X-ray absorption spectroscopy at the Sb K-edge [4], the possibility of an Sbpyrochlore being the final responsible for the actual coloring was advanced, despite antimony being added during the manufacture process as bindheimite, Sb2Pb 2O7 (giallo di Napoli ). An analysis is presented on the two possible crystallographic descriptions for a pyrochloretype array under the usual cubic space group that could account for an anomalous intensification of 111 reflection for Sb-pyrochlore within the glaze and simulataneously correlate with XANES data.