Lanthanide Cation Size-Driven Trigonal-to-Monoclinic-to-Orthorhombic Transition in a Series of Quaternary Zirconium Molybdates: Crystal Growth, Optical, and Magnetic Investigation

The crystal growth of two families of lanthanide zirconium molybdates exhibiting luminescence properties is reported. Crystals of Ln 2 Zr 3 (MoO 4 ) 9 (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd) and Ln 2 Zr 2 (MoO 4 ) 7 (Ln = Tb, Dy) were obtained by the molten flux growth technique. Ln 2 Zr(MoO 4 ) 5 (Ln = Ho, Er, Tm, Yb, Y) were synthesized by solid-state reactions. The compounds Ln 2 Zr 3 (MoO 4 ) 9 (Ln = La- Nd, Sm–Gd) crystallize in the space group R 3̅ c with lattice parameters of a = b = 9.85200(10)–9.78700(10), c = 59.1112(9)–57.9131(10) Å. The second class of compounds Ln 2 Zr 2 (MoO 4 ) 7 (Ln = Tb, Dy), crystallize in the space group C 2/ c with lattice parameters of a = 20.7457(4)–20.7015(4) Å, b = 9.8556(2)–9.8395(2) Å, c = 13.8424(3)–13.8261(2) Å, and β = 113.5210(10)–113.5440(10)°. The third class of compounds, Ln 2 Zr(MoO 4 ) 5 (Ln = Ho, Er, Tm, Yb, Y), crystallizes in the space group Cmc 2 1 with lattice parameters of a = 21.031(2)–20.824(4) Å, b = 9.7473(5)–9.6540(2) Å, and c = 9.7961(9)–9.l7420(2) Å. The structures consist of frameworks where LnO 9 and ZrO 6 polyhedra are connected with MoO 4 groups via corner-sharing. Solid-state reactions were used to make bulk polycrystalline samples for property measurements. Optical properties of Ce 2 Zr 3 (MoO 4 ) 9, Sm 2 Zr 3 (MoO 4 ) 9, Eu 2 Zr 3 (MoO 4 ) 9, and Tb 2 Zr 2 (MoO 4 ) 7 were investigated. In addition, the magnetic properties of Ce 2 Zr 3 (MoO 4 ) 9, Sm 2 Zr 3 (MoO 4 ) 9, Gd 2 Zr 3 (MoO 4 ) 9, and Tb 2 Zr 2 (MoO 4 ) 7 are reported.