A tetragonal form of dysprosium orthomolybdate at room temperature

In the present tetragonal modification of dysprosium orthomolybdate, Dy 2 (MoO 4 ) 3 , the Dy, one Mo and one O atom are located on a mirror plane with Wyckoff symbol 4 e , while another Mo atom is located on a fourfold inverse axis, Wyckoff symbol 2 a . A single crystal was selected from a polycrystalline mixture of the Dy 2 O 3 –ZrO 2 –MoO 3 system and was stable at room temperature for at least three months. The structure refinement does not indicate the presence of Zr on the Dy sites (to within 1% accuracy). Thus, the stabilization of the tetragonal form is due to disordered positions for a second O atom and split positions for a third O atom that also maintain the DyO 7 coordination, which is not expected for short Dy—O distances [2.243 (6)–2.393 (5) Å].