Influence of Fluoride Addition on α-Alumina Formation from Aluminum Hydroxide

Abstract

The DTA curve of coarse particles of gibbsite showed an exothermic peak at 1234°C, corresponding to the phase transformation of θ-alumina to α-alumina. The exothermic peak disappeared on the DTA curve of the sample with an addition of 2mass% of AlF₃. The main crystalline phase of the heating samples has already transformed into α-alumina at 1000°C. The addition of AlF₃ caused to shift the phase transformation of alumina to lower temperature side and moreover the transformation phenomenon to α-alumina to be sluggish.