Synthesis, crystal structure, magnetic and luminescence properties of KEuGe2O6: a europium cyclogermanate containing infinite chains of edge-sharing Eu-O polyhedra

A new Eu(III) germanate, KEuGe2O6, has been synthesized by both the flux-growth method and the high-temperature, high-pressure hydrothermal method and characterized by single-crystal X-ray diffraction. The compound contains parallel zigzag chains of edge-sharing Eu-O polyhedra, which are in turn linked by sharing vertices and edges with three-membered single ring Ge3O9(6-) germanate anions to form a 3-D framework structure. The magnetic and luminescence properties were also investigated. The observed chiMT value at 300 K is 4.53 emu K mol(-1), which is in good agreement with the calculated value for three Eu3+ ions. The sharp peaks in the room-temperature emission spectrum are assigned. The number of lines in the region of the 5D0-->7F0 transition and the relative intensities of the 5D0-->7F1 and 5D0-->7F2 transitions confirm the presence of two local Eu3+ environments and strongly distorted Eu3+-ligand surroundings. The reasons for the very short emission life time is discussed. The Sm and Tb analogues have also been synthesized.