ChemInform Abstract: The Crystal Structure of the Potential Ferroelectric Calcium Rhenate(VI, VII) Ca₁₁Re₄O₂₄ and Its Relation to the Structure of Sr₁₁Os₄O₂₄.

Abstract

structure structure (solids and liquids) D 2000 -012The Crystal Structure of the Potential Ferroelectric Calcium Rhenate(VI, VII) Ca 11 Re 4 O 24 and Its Relation to the Structure of Sr 11 Os 4 O 24 .-The structure of the title compound, obtained by thermal decomposition of Ca 5 Re 2 O 12 in a dynamic vacuum, is determined by single crystal X-ray data (space group I4 1 , Z = 4). The Re atoms occupy two crystallographic sites, both with octahedral oxygen coordination and the Ca atoms occupy seven different sites with 8, 9, or 10 oxygen neighbors. The structure is closely related to that of Sr 11 Os 4 O 24 , which crystallizes in the centrosymmetric, monoclinic space group I2/a. It is suggested that both compounds crystallize in the common higher symmetry group I4 1 /a at higher temperatures. The title rhenate shows Curie-Weiss behavior but no superconducting transition down to 2 K. -(JEITSCHKO, W.; MONS, H. A.; RODEWALD, U. CH.; MOELLER, M. H.

A Family of A-Site Cation-Deficient Double-Perovskite-Related Iridates: Ln9Sr2Ir4O24 (Ln = La, Pr, Nd, Sm)

“…Several compositions isostructural with Sr x La 11−x Ir 4 O 24 are known, including A 11 Re 4 O 24 (A = Ca, Sr) 25,26 type with a magnetic ion on the A site have been reported. In the absence of a magnetic ion on the A site, any magnetic property observed is due to the presence of iridium on the B site, and any magnetic order would be the result of magnetic exchange coupling between them.…”