The Thermal Decomposition of Ammonium Hexafluoroferrate(III) and Ammonium Hexafluoroaluminate. A New Crystalline Form of Aluminum Fluoride

Abstract

Ammonium hexafluorof errate(III), (NH4)3FeFe, and ammonium hexafluoroaluminate, (NH4)3A1F6, decompose 011 heating with an initial loss of 2 moles of ammonium fluoride, forming ammonium tetrafluoroferrate(III), iXHaFeFa (at ca. 140°), and ammonium tetrafluoroaluminate, NHaAlF4 (at ca. 170'). Further heating results in the gradual loss of ammonium fluoride, the final products being iron(II1) fluoride mixed with oxide (at ca. 285") and ?-aluminum fluoride, a new crystalline form (at ca. 300').The intermediate, ammonium tetrafluoroferrate(III), was found to be tetragonal, a = 3.78, c = 6.36 A. It can also be prepared by direct reaction of iron(II1) fluoride and ammonium fluoride a t 180".The structural relationships of the compounds are discussed.

Ammonium fluorolanthanates: solid state synthesis, infrared spectral and X-ray diffraction data

“…By analogy with Fe and A1 analogs (13,14), the ammonium fluorolanthanate structure may be visualized as layers of LnF, octahedra (built up by mutual sharing of corners and edges) with interleaving layers of NH, groups. The splitting of v3 and v, modes in the octahedral LnF,3-suggests a distorted configuration.…”

Controlled Morphology Synthesis of Nanostructured β-AlF3–x(OH)x with Tunable Specific Surface Area

“…Nanosized crystalline β-AlF 3– x (OH) x can be prepared by several different synthesis approaches such as sol–gel fluorolytic process, nonaqueous route, thermal decomposition of α-NH 4 AlF 4 , dehydration of α-AlF 3 ·H 2 O, thermal treatment of α-AlF 3 ·3H 2 O nanorods in air atmosphere, oxidative decomposition of N 2 H 6 AlF 5 , plasma-fluorination syntheses, or hydro­(solvo)­thermal synthesis . The microwave (MW)-assisted solvothermal synthesis method developed by Demourgues et al was shown to be very efficient to prepare rapidly pure nanostructured hydroxyfluorides AlF 3– x (OH) x · n H 2 O. , These authors also showed the relationships between the OH rate inside the anion framework, strongly dependent of the [HF]/[Al] precursor molar ratio, and the nature of the obtained allotropic form.…”

“…Water molecules can be located in these hexagonal tunnels and can be eliminated with an appropriate thermal treatment at temperatures from 110 to 380 °C. 17 Nanosized crystalline β-AlF 3−x (OH) x can be prepared by several different synthesis approaches such as sol−gel fluorolytic process, 18 nonaqueous route, 19 thermal decomposition of α-NH 4 AlF 4 , 20 dehydration of α-AlF 3 •H 2 O, 21 thermal treatment of α-AlF 3 •3H 2 O nanorods in air atmosphere, 22 oxidative decomposition of N 2 H 6 AlF 5 , 23 plasma-fluorination syntheses, 24 or hydro(solvo)thermal synthesis. 25 The microwave (MW)assisted solvothermal synthesis method developed by Demourgues et al was shown to be very efficient to prepare rapidly pure nanostructured hydroxyfluorides AlF 3−x (OH) x • nH 2 O.…”

Thermal analysis of complex fluorides

“…In an inert and in an oxidative atmosphere respectively, the reactions are: 3NH4MnF4-,3MnF2 + 1/2N2 + 2 NH3 + 6HF NH4MnF4 + 1/202-*MnF2 + 1/2N2 + 2 HF + H20 Additionally a polymorphic transition to a high temperature cubic form of (NH4)3MnF6 has been detected at 92 ~ Iron again behaves as the most elements with the following decomposition scheme [7]: For (NH4)3MF6 type of compounds the TG curves can obviously not be used to predict the reaction pathway. There are only isothermal measurements at low enough temperatures which can give the answer to these questions.…”