AgCu₃V₄O₁₂: a Novel Perovskite Containing Mixed-Valence Silver ions

A novel silver-containing perovskite, AgCu3V4O12, was synthesized under high-pressure and high-temperature conditions. It crystallizes in an A-site-ordered perovskite structure (space group Im3̅), in which silver ions occupy the 12-coordinated A sites forming regular icosahedra, and exhibits metallic behavior. Bond-valence-sum calculations and X-ray photoemission spectroscopy reveal that Ag ions are present in the mixed-valence state, most likely attributable to the coexistence of Ag+ and Ag3+, unlike the case of well-known perovskite-type AgNbO3 and AgTaO3 containing only Ag+ ions. We discuss metallic conduction in relation to electronic structure calculations.