Characterization for α-Al₂O₃ and Some Hydrated Aluminas by Fourier Transform Infrared Photoacoustic Spectroscopy

Abstract

α-Al₂O₃ and three hydrated aluminas were studied by photoacoustic spectroscopy (PAS).
Hydrargillite (α-Al(OH)₃), boehmite (α-AlO(OH)) and bayerite (β-Al(OH)₃) showed different absorption patterns in the -OH stretching and bendings.
(1) PAS data for hydrargillite, boehmite and bayerite in the wave length region from 400 to 4000cm^-1 are relatively consistent with previously reported data.
(2) The spectrum of hydrargillite consists of five main -OH stretching bands at 3620, 3525, 3446, 3393 and 3379cm^-1. These bands shifted slightly from the reported IR spectroscopic data, suggesting some diferrences in OH band length.
(3) The spectrum of η-Al₂O₃ obtaine by heating bayerite at 700°C in good agreement with that of boehmite.
(4) PAS is a useful tool for the characterization of dehydrated and hydrated aluminas.