Characterization of beryllium selenates by X-ray powder diffraction, DTA and DSC

✍ Scribed by V. G. Koleva; V. A. Karadjova; M. P. Georgiev

• Publisher: John Wiley and Sons
• Year: 2004
• Tongue: English
• Weight: 114 KB
• Volume: 39
• Category: Article
• ISSN: 0232-1300
• DOI: 10.1002/crat.200410287

✦ Synopsis

BeSeO 4 .2H 2 O and BeSeO 4 have been studied röntgenographically: BeSeO 4 .2H 2 O 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) Å 3 . The crystals of BeSeO 4 are tetragonal: a = 4.648(1) Å; c = 7.084 (3) Å; V = 153.1(1) Å 3 , SG I4. The thermal dehydration of BeSeO 4 .4H 2 O has been studied by TG, DTA and DSC methods. The dehydration occurs in four steps and intermediate hydrates BeSeO 4 .2H 2 O, BeSeO 4 .H 2 O and BeSeO 4 .0.5H 2 O are formed. The enthalpies of dehydration of the observed dehydration processes have been determined. The higher value of ∆H deh of BeSeO 4 .4H 2 O as compared to those of other metal selenate tetrahydrates is discussed in terms of the strong Be-H 2 O interaction. The enthalpies of formation of BeSeO 4 .4H 2 O and BeSeO 4 .2H 2 O have been calculated.