Fluorinated transition alumina with Al2−x/3O3−xFx compositions: Thermal, chemical, structural and morphological investigations

Fluorinated transition aluminas (Al2−x/3O3−xFx) with hexagonal platelet shape were synthesized via decomposition of α-AlF3 under air; they are thermally stable up to 1000 °C and exhibit at 1150 °C a weight loss with volume reduction caused by fluorine departure corresponding to a phase transition toward corundum alumina. The different characterizations performed in this study are structural (XRD), chemical (TGA-MS and microprobe analysis) and morphological (SEM, TEM and dilatometry). The evidence provided from this study is consistent with the formation of an Al–O–F phase as an intermediate compound in the pyrohydrolysis of an aluminium trifluoride phase to α-Al2O3.