Synthesis and crystal structure of Eu_2ReO_5, a complex oxide with Re-Re pairs in a tetragonal antiprismatic coordination

摘要

The europium rhenium oxide Eu_2ReO_5 has been synthesized by solid state reaction of Eu_3ReO_8 with metallic rhenium and europium oxide Eu_2O_3 at 1450 K in sealed silica ampoules. The crystal structure was determined by X-ray diffraction analysis on a twinned specimen. It crystallizes in the tetragonal space group P4 (No.85, a=865.3(1) pm, c=573.9(1)) pm; Z=4). The main feature of the crystal structure is the formation of Re-Re pairs surrounded by eight oxygen atoms in a tetragonal antiprismatic configuration. The Re_2O_ 8 units are stacked building columns ~1_infinity(Re_2O_8-Re_2O_8) running along (001). The compound is a semiconductor with an optical band gap of 1.4 eV.