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 Ln2Zr3(MoO4)9 (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd) and Ln2Zr2(MoO4)7 (Ln = Tb, Dy) were obtained by the molten flux growth technique. Ln2Zr(MoO4)5 (Ln = Ho, Er, Tm, Yb, Y) were synthesized by solid-state reactions. The compounds Ln2Zr3(MoO4)9 (Ln = La- Nd, Sm–Gd) crystallize in the space group R3̅c 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 Ln2Zr2(MoO4)7 (Ln = Tb, Dy), crystallize in the space group C2/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, Ln2Zr(MoO4)5 (Ln = Ho, Er, Tm, Yb, Y), crystallizes in the space group Cmc21 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 LnO9 and ZrO6 polyhedra are connected with MoO4 groups via corner-sharing. Solid-state reactions were used to make bulk polycrystalline samples for property measurements. Optical properties of Ce2Zr3(MoO4)9, Sm2Zr3(MoO4)9, Eu2Zr3(MoO4)9, and Tb2Zr2(MoO4)7 were investigated. In addition, the magnetic properties of Ce2Zr3(MoO4)9, Sm2Zr3(MoO4)9, Gd2Zr3(MoO4)9, and Tb2Zr2(MoO4)7 are reported.