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 4e, while another Mo atom is located on a fourfold inverse axis, Wyckoff symbol 2a. 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].