X-RAY SINGLE-CRYSTAL STRUCTURE-ANALYSIS OF THE 3-LEG-LADDER COMPOUND (SR,CA)(4)CU6O10

Crystals with the general formula Srn-1Cun+1O2n belong to the ''ladder '' compounds, a new series of high-pressure materials. They are expect ed to have interesting magnetic properties and are possible candidates for HT, superconductors. For the first time single crystals of (Sr, C a)(4)Cu6O10 have been grown using a high-Ar-gas-pressure method. A cry stal was measured on an X-ray four circle single crystal diffractomete r and the structure was refined to R = 0.056 with F data and wR = 0.09 4 with F-2 data. (Sr, Ca)(4)Cn(6)O(10) crystallizes with space group N o. 65 Cmmm (Z = 1) and has lattice parameters a = 3.9299(5) Angstrom, b = 19.392(3) Angstrom, c = 3.4358(5) Angstrom. The Ca content at the Sr site was refined to 4.3(8)%. The crystal structure consists of laye rs with coupled chains formed by both edge-and corner-sharing CuO4 uni ts (''ladders'') separated by layers of Sr/Ca atoms. (C) 1997 Academic Press.