The characterization of the thermal behaviour of inorganic fluorides using quasi-static thermoanalytical methods

Abstract

Quasi-static thermal analysis is very useful for the characterization of the thermal behaviour of inorganic fluorides. The strong dependence of the thermal decomposition of hydroxonium fluorometallates, monofluorophosphates, and ammonium fluorometallates on the partial pressure is demonstrated. Non-reciprocal quasi-isobaric investigations are specially suitable to disclose this behaviour. The possibilities of characterization of the reaction mechanism using quasi-static thermal analytical methods as well as the use of these methods as synthetic variants for phase-pure fluorides are demonstrated by further examples. In this context the repression of the amount of hydrolysis products is discussed.

Investigation of Fe-based oxyhydroxy-fluoride with hollandite-type structure

“…The thermal degradation of the different compounds was followed by a thermogravimetric analyzer (Setaram TAG 24) coupled with a quadripolar mass spectrometer (Balzers Thermostar) which allowed to detect HF (M F = 19 g) and water ðM H 2 O ¼ 18 gÞ release [11]. Each sample was heated under argon atmosphere (heating rate 1 K/min).…”

Synthesis and characterization of Al3+, Cr3+, Fe3+ and Ga3+ hydroxyfluorides: correlations between structural features, thermal stability and acidic properties

“…b-FeF 32x (OH) x ? zH 2 O and b-Fe 12x Cr x F 32y (OH) y ?zH 2 O (x ~0.1 and 0.2) were prepared from their homologous trihydrated fluorides, under a ''self-generated'' atmosphere 15 at 493 K for 16 hours. The starting material FeF 3 ?3H 2 O was obtained from an alcoholic iron(III) nitrate solution, as described above.…”

“…14,17 The best route was the thermal decomposition of (NH 4 ) 3 CrF 6 ?dH 2 O under a ''self-generated'' atmosphere. 15 Moreover, in order to avoid the presence of any ammonium group which would generate basic properties in the final material, another route was developed. Cr(OH) 3 ?3H 2 O reactant was prepared by precipitation from an aqueous chromium(III) nitrate solution.…”

Anionic Ordering and Thermal Properties of FeF3·3H2O

“…11 However, it also revealed that the HTB phase exhibits a narrow range of stability with respect to temperature since the decomposition process can yield α-FeF 3 . The range of existence of intermediate compositions/structures can be extended by means of the self-generated atmosphere method, 28 where the decomposition of the metal fluoride hydrate takes place in a closed container.…”