Transition metal iodates. VII. Crystallographic and nonlinear optic survey of the 4 f-iodates

Abstract

Thirteen crystallographically distinct families of 4 f-iodates, including hydrates, have been investigated. The anhydrous Type I family, extending from Ce to Lu, crystallizes in the monoclinic system, space group P2 1 a : The lattice constants of Gd(IO 3) 3, for example, are a = 13.389 ± 0.006, b = 8.500 ± 0.002, c = 7.106 ± 0.002 Å, β = 99.73 ± 0.03° with four formulas per unit cell. Yb(IO 3) 3 and Lu(IO 3) 3 also crystallize in Type II with monoclinic space group P2 1 c and lattice constants for Yb(IO 3) 3 of a = 8.685 ± 0.005, b = 6.066 ± 0.002, c = 16.687 ± 0.009 Å, β = 115.01 ± 0.18°, and four formulas per unit cell. Polycrystalline samples only of the anhydrous Types III, IV, V, and VI have been prepared and typical powder patterns are given. All anhydrous 4 f-iodates form in centrosymmetric space groups. La and Ce grow as hemihydrates in the orthorhombic space group C222 1, with a = 19.26 ± 0.01, b = 7.40 ± 0.01, c = 6.76 ± 0.01 for La(IO 3) 3· 1 2 H 2O , and both generate second harmonics more efficiently than quartz. Ce, Pr, Nd, Pm, and Sm form monohydrates, space group P2 1, with lattice constants for Sm(IO 3) 3·H 2O of a = 10.080 ± 0.007, b = 6.642 ± 0.006, c = 7.250 ± 0.008 Å, β = 112.9 ± 0.1°, and two formulas per unit cell. The monohydrates are also more efficient than quartz at generating second harmonics. Two dihydrated families grow: Type I from Tm to Lu and Type II from Nd to Er, both triclinic. Lu(IO 3) 3·2H 2O has a = 8.018 ± 0.012, b = 9.956 ± 0.021, c = 6.969 ± 0.016 Å, α = 99.8 ± 0.2°, β = 93.8 ± 0.2°, γ = 68.2 ± 0.2° with two formulas in the unit cell, space group P 1 . Nd(IO 3) 3·2H 2O has a = 7.56 ± 0.04, b = 10.77 ± 0.05, c = 7.34 ± 0.02 Å, α = 105.3 ± 0.4°, β = 110.8 ± 0.7°, γ = 97.9 ± 0.6° with two formulas per cell and space group P 1 . Polycrystalline Gd to Lu(IO 3) 3·4H 2O, and Ce to Sm(IO 3) 3·5H 2O Type I form in centrosymmetric space groups; powder patterns for two tetrahydrates and the four pentahydrates are given. La(IO 3) 3·5H 2O and Pr(IO 3) 3·5H 2O, Type II, are monoclinic, space group P2 1 m , with lattice constants for Pr(IO 3) 3·5H 2O of a = 6.768 ± 0.008, b = 23.120 ± 0.039, c = 7.107 ± 0.007 Å, β = 112.7 ± 0.1°, and four formulas per unit cell.