ISSN:
0044-2313
Keywords:
Gadolinium compounds
;
preparation
;
crystal structures
;
DTA-TG analysis
;
X-ray powder pattern
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Description / Table of Contents:
Structure and Thermal Behaviour of Gadolinium(III)-sulfate-octahydrate Gd2(SO4)3 · 8 H2O.Gd2(SO4)3 · 8 H2O crystallizes monoclinic with space group C2/c and the lattice constants a = 13.531(7), b = 6.739(2), c = 18.294(7) Å, β = 102.20(8)°. In the structure Gd is coordinated by 4 oxygen atoms of crystal water and 4 oxygens of sulfate giving rise to a distorted square antiprism. During DTA-TG-experiments the title compound first loses crystal water in a two-step mechanism in the temperature range 130-306°C. The resulting Gd2(SO4)3 is amorphous and recrystallization occurs in the range 380-411°C. The so-obtained low-temperature modification β-Gd2(SO4)3, undergoes a monotropic phase transition at about 750°C to the high-temperature form α-Gd2(SO4)3. The powder pattern of this modification was indexed based on monoclinic symmetry with space group C2/c and lattice constants a = 9.097(3), b = 14.345(5), c = 6.234(2) Å, β = 97.75(8)°. The hightemperature modification of gadolinium-sulfate shows decomposition to Gd2O2SO4 at 900°C and, subsequently, decomposition at 1 200°C yields the formation of C-Gd2O3.
Notes:
Gd2(SO4)3 · 8 H2O kristallisiert monoklin in der Raumgruppe C2/c mit den Gitterkonstanten a = 13,531(7), b = 6,739(2), c = 18,294(7) Å und β = 102,20(8)°. In der Struktur ist Gd von je 4 Sauerstoffatomen des Hydratwassers und der Sulfationen in Form eines stark verzerrten quadratischen Antiprismas umgeben. Im DTA-TG-Experiment verliert Gd2(SO4)3 · 8 H2O in einem zweistufigen Prozeß im Temperaturbereich 130-306°C zunächst Kristallwasser; anschließend tritt zwischen 380 und 411°C Rekristallisation des amorphen Gd2(SO4)3 unter Bildung der Tieftemperaturmodifikation β-Gd2(SO4)3 auf. Bei ca. 750°C wird monotrop die Hochtemperaturmodifikation α-Gd2(SO4)3 gebildet. Aus der Analyse der Pulverdaten folgt monokline Symmetrie mit der Raumgruppe C2/c und den Gitterkonstanten a = 9,097(3), b = 14,345(5), c = 6,234(2) Å und β = 97,75(8)°. Ab ca. 900°C beginnt die Zersetzung von α-Gd2(SO4)3 zu Gd2O2SO4 und ab 1 200°C liegt C-Gd2O3 vor.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/zaac.19936190429
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