An ordered oxygen deficient K2NiF4 structure: Pb2Sr2CuFeO6
Abstract
An oxygen deficient K2NiF4-type oxide, Pb2Sr2CuFeO6, containing CuI only, has been synthesized for the first time. It crystallizes in the orthorhombic system, with a= 5.4604(3)Å, b= 5.5227(3)Å and c=12.2112(6)Å. This phase, isotypic to Pb2Sr2–XLaXCu2O6, consists of single perovskite layers of FeO6 octahedra, single rock salt layers and layers of CuO2 sticks. Structural study allows a model to be proposed for the [PbO] layers, which are built up from zig–zag PbO chains, similar to those of PbO–massicot, forming corner-sharing PbO3L tetrahedra (L = 6s2 lone pair). This phase intercalates oxygen, leading to the oxide Pb2Sr2CuFeO6+δ, with δ ranging from 0 to 1.8, that exhibits a superstructure, 4a× 4b× 2c. The intercalation of oxygen is completely reversible, returning to the initial phase upon annealing Pb2Sr2CuFeO7.8 in a nitrogen flow.
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