Characterization of beryllium selenates by X-ray powder diffraction, DTA and DSC
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2004-11-01
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Abstract
BeSeO4.2H2O and BeSeO4 have been studied röntgenographically: BeSeO4.2H2O forms orthorhombic / crystals with lattice constants: a = 5.843(2) Å; b = 9,790(3) Å; c = 4.692(1) Å; V = 268.4(1) Å3. The crystals of BeSeO 4 are tetragonal: a = 4.648(1) Å; c = 7.084 (3) Å; V= 153.1(1) Å3, SG I4̄. The thermal dehydration of BeSeO 4.4H2O has been studied by TG, DTA and DSC methods. The dehydration occurs in four steps and intermediate hydrates BeSeO 4.2H2O, BeSeO4.H2O and BeSeO 4.0.5H2O are formed. The enthalpies of dehydration of the observed dehydration processes have been determined. The higher value of ΔHdeh of BeSeO4.4H2O as compared to those of other metal selenate tetrahydrates is discussed in terms of the strong Be-H2O interaction. The enthalpies of formation of BeSeO 4.4H2O and BeSeO4.2H2O have been calculated. © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.