Ytterbium(III) selenate is an inorganic compound of ytterbium and the selenate ion, with the chemical formula Yb2(SeO4)3. Both anhydrous and hydrated forms are known, including the well-characterized octahydrate Yb2(SeO4)3·8H2O.
Preparation Ytterbium(III) selenate can be prepared by reaction of ytterbium(III) oxide, hydroxide or carbonate with selenic acid. For example:
Yb2O3 + 3 H2SeO4 → Yb2(SeO4)3 + 3 H2O
Crystallization from aqueous solution gives the octahydrate.
Properties Structure Anhydrous Yb2(SeO4)3 crystallizes in the monoclinic crystal system, in space group P21/n (No. 14). Its lattice parameters are a = 9.220(2) Å, b = 9.521(2) Å, c = 12.886(3) Å and β = 91.04(1)°.Iskhakova, L. D.; Ovanisyan, S. M. "Synthesis and structure of Yb2(SeO4)3." Zhurnal Neorganicheskoi Khimii. 1995. 40 (11): 1768–1772.
The structure is built from Yb–O coordination polyhedra and SeO4 tetrahedra linked through shared oxygen atoms.
The octahydrate also crystallizes in the monoclinic system, but in space group C2/c. Reported lattice parameters are a = 13.704(6) Å, b = 6.831(3) Å, c = 18.507(7) Å and β = 101.90(3)°.
In the octahydrate, Yb3+ is eight-coordinate, with oxygen atoms supplied by selenate groups and water molecules.
Thermal decomposition On heating, ytterbium(III) selenate octahydrate first loses its water of crystallization to form the anhydrous selenate.
Further heating causes reduction of selenium from Se(VI) to Se(IV), producing ytterbium(III) selenite as an intermediate. Continued decomposition ultimately gives ytterbium(III) oxide.
The general sequence can be represented as:
Yb2(SeO4)3·8H2O → Yb2(SeO4)3 → Yb2(SeO3)3 → oxide–selenite intermediates → Yb2O3
Magnetic properties Magnetic-susceptibility studies of Yb2(SeO4)3·8H2O have been interpreted in terms of crystal-field splitting of the Yb3+ ground multiplet. The local environment of Yb3+ can be approximated as having tetragonal symmetry for magnetic modelling, although the actual crystal structure is monoclinic.
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