Dysprosium(III) selenate is an inorganic compound of dysprosium and the selenate ion, with the chemical formula Dy2(SeO4)3. The best-characterized hydrated form is the octahydrate, Dy2(SeO4)3·8H2O.
Preparation Dysprosium(III) selenate can be prepared by reaction of a soluble dysprosium(III) compound or dysprosium(III) oxide with selenic acid, followed by crystallization from aqueous solution.
The octahydrate belongs to a continuous series of rare-earth selenate octahydrates formed by the heavier lanthanides.Rosso, Bernard; Perret, René. "X-ray crystallographic study of selenate octahydrates of the rare earths from samarium to lutetium." Comptes Rendus de l'Académie des Sciences, Série C. 1970. 270 (11): 997–999.
Structure and properties Dysprosium(III) selenate octahydrate crystallizes in the monoclinic crystal system and is isostructural with the octahydrates of the other heavy rare-earth selenates.
The structure contains Dy3+ coordination polyhedra linked to SeO4 tetrahedra, with coordinated water molecules completing the dysprosium coordination environment.
Infrared spectra show the characteristic internal vibrational modes of SeO42− tetrahedra together with the O–H vibrations of the water molecules.
Thermochemical data have also been reported for Dy2(SeO4)3·8H2O; the OECD/NEA review gives an adopted standard enthalpy of formation of −5371.4 ± 17.5 kJ mol−1, though it notes that the underlying experimental source is of uncertain quality.
Thermal decomposition On heating, the octahydrate first loses its water of crystallization to form anhydrous Dy2(SeO4)3.
Further heating causes reduction of selenium from Se(VI) to Se(IV), producing dysprosium(III) selenite:
Dy2(SeO4)3 → Dy2(SeO3)3 + O2
The selenite subsequently decomposes through oxide–selenite intermediates before ultimately yielding dysprosium(III) oxide, Dy2O3.Belik, N. P.; Serebrennikov, V. V. "Thermal stability of rare earth selenates". Trudy Tomskogo Universiteta. 1971. 204: 285–288.
Reactions Heating dysprosium selenate-derived material with lithium fluoride can produce the mixed fluoride–selenite Dy3(SeO3)4F.
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