Aluminium Fluoride

Brief Overview

Aluminum fluoride (AlF₃) is an inorganic compound used primarily in the production of aluminum. This colorless solid can be prepared synthetically but also occurs in nature. This substance is an odorless white crystalline powder and stable under ordinary conditions. 

Manufacturing Process

There are three main processes to manufacture aluminium fluoride:

1. By heating ammonium hexafluoro aluminate to red heat in a stream of nitrogen
2. Obtained by the action of fluorine or hydrogen fluoride on the metal at high temperatures, or by fusing cryolite or sodium fluoride with aluminium sulfate
3. The action of hydrogen fluoride gas on alumina trihydrate; the reaction of hydrogen fluoride on a suspension of aluminium trihydrate, followed by calcining the hydrate formed; the reaction of fluosilicic acid on aluminium hydrate.

Metal Industry

Aluminum fluoride is an important additive for the production of aluminum by electrolysis. Together with cryolite lowers the melting point to below 1000 °C and increases the conductivity of the solution. It is into this molten salt that aluminum oxide is dissolved and then electrolyzed to give bulk Al metal.

Ceramics and Glass Industry

Aluminium fluoride plays a great role in ceramic production as it is the main chemical compound used in glazes for finished products. Besides that, aluminium fluoride is also used to create refractory ceramic products. In glass industry, aluminium fluoride is used as a filler.

Other Applications

Together with zirconium fluoride, aluminum fluoride is an ingredient to produce fluoroaluminate glasses. Furthermore, it is used to inhibit fermentation and serves as a sputtering target for the preparation of low index films. Fluoride compounds are used in coatings for the UV to middle-IR regions. They provide the lowest refractive indices and therefore are essential components of anti-reflective coatings.