RAMAN-STUDY OF THE FORMATION OF TRANSITION ALUMINA SINGLE-CRYSTAL FROM PROTONIC BETA-BETA''-ALUMINAS

In this letter Raman scattering is used for the first time to check transitions in alumina. Above 1000°C the growth of α-alumina is obvious both in Raman and in IR spectra. We also observed the disappearance of the Al-O-OH+ modes above 900 cm-1. The gradual transition between β(β″) alumina and spinel-like transition alumina is associated with a band-broadening due to an increase of the local disorder. On the other hand, the syntactic nucleation of α-alumina shows no structural relation as far as the vibrational properties are concerned. This behavior is not surprising, the oxygen stacking planes being different in spinel and corundum structures.