A new neodymium molybdate, Nd 6 Mo 10 O 39 , has been identified in the Nd 2 O 3 -MoO 3 phase system. Nd 6 Mo 10 O 39 appears to be a metastable phase, which does not form directly from a stoichiometric mixture of Nd 2 O 3 and MoO 3 oxides. Instead, it can be obtained by thermal decomposition of Nd 2 Mo 4 O 15 . Nd 2 Mo 4 O 15 usually decomposes into Nd 2 (MoO 4 ) 3 , and the formation of Nd 6 Mo 10 O 39 critically depends on the heating regime used.
The structure of Nd 6 Mo 10 O 39 has been determined by single crystal X-ray diffraction. It crystallizes in the monoclinic space group C2/ c, with unit cell parameters of a ¼ 12:425ð1Þ Å, b ¼ 19:860ð2Þ Å, c ¼ 13:882ð1Þ Å, b ¼ 100:767ð2Þ1, V ¼ 3365:2ð5Þ Å3 at 120 K. Nd atoms are seven and eight coordinate, and pairs of coordination polyhedra share edges and faces, respectively, to form Nd 2 O 12 and Nd 2 O 13 groups. All Mo atoms are in tetrahedral coordination environments, with some of the tetrahedra sharing corners to form pyromolybdate groups.