Crystal structures of two sodium yttrium molybdates: NaY(MoO4)2and Na5Y(MoO4)4

The crystal structure of NaY(MoO4)2 has been determined from powder X-ray diffraction data [space group I41/a, Z= 2, a= 5.19890(5)Å, c= 11.3299(1)Å]. The Na and Y atoms are disordered over the eight-coordinate sites of a scheelite structure. The crystal structure of Na5Y(MoO4)4 has been determined from single-crystal X-ray diffraction data [space group I41/a, Z= 4, a= 11.374(3)Å, c= 11.440(5)Å] and found to be scheelite related, with the tetrahedral sites occupied by, an ordered arrangement of Mo and Na in a 4 : 1 ratio. Comparisons are drawn between the structures of these two closely related phosphor materials.