A STRUCTURAL STUDY OF AMORPHOUS ALUMINUM PHOSPHATE THIN-FILMS BY X-RAY-ABSORPTION SPECTROSCOPY

We have undertaken in this study to outline the amorphous structure of aluminium phosphate thin film obtained from the pyrosol process. The X-ray absorption measurements carried out at the aluminium and phosphorus K-edges enabled us to characterize the local surroundings of these atoms in the untreated deposits and in the annealed ones. Our experimental results allow us to suggest that the structure of these thin films is constituted of two types of chain [O-Al-O-P]n and [O-Al-O-Al]n, with Al atoms in both tetrahedral and octahedral sites. This certainly leads to the formation of two types of aggregate: the first based on the structure of tridymite AlPO4 recrystallizing in this form when annealed, and the second based on the structure of amorphous alumina, would become largely predominant in aluminium-rich deposits and would not recrystallize at 900-degrees-C.