From Ag₂Sb₂O₆ to Cd₂Sb₂O₇: Investigations on an anion-deficient to ideal pyrochlore solid solution

Abstract

A complete solid solution between the anion-deficient pyrochlore Ag₂Sb₂O₆ and the ideal pyrochlore Cd₂Sb₂O₇ has been synthesized through the standard solid state ceramic method. Each composition has been characterized by various different techniques, including powder X-ray diffraction, optical spectroscopy, electron paramagnetic resonance and ¹²¹Sb Mössbauer spectroscopy. Computational methods based on density functional theory complement this investigation. Photocatalytic activity has been studied, and transport properties have been measured on pellets densified by spark plasma sintering. The analysis of the data collected from these various techniques enables a comprehensive characterization of the complete solid solution and revealed an anomalous behavior in the Cd-rich end of the solid solution, which has been proposed to arise from a possible radical O⁻ species in small concentrations.Keywords: Cd₂Sb₂O₇, Thermogravimetric analysis, Ag₂Sb₂O₆, ¹²¹Sb Mössbauer spectroscopy, Optical properties, Pyrochlor