Barium oxide as a modifier to stabilize the γ-Al₂O₃ structure

This research concentrated on the structural stability of γ-alumina (γ-Al₂O₃) was investigated by a combination of differential thermal analysis, X-ray diffractometry and surface-area measurements. The γ –to– θ and then α phase transitions were observed as an exothermic peak at 1000°C–1400°C in the DTA curves. The role of barium oxide as a modifier to stabilize γ-Al₂O₃ structure has been investigated. XRD measurements show that after calcination at 1000°C for 2 h, a significant fraction of the pure γ-Al₂O₃ (BaO-free) transformed to θ-Al₂O₃ while that the transition phase in alumina samples modified by BaO have been reduced significantly. Barium oxide, eliminate pentacoordinated aluminum ions through coordinative saturation and alter these ions into octahedral cations and effectively suppressed the γ –to– α phase transition in Al₂O₃, which concluded as improving the thermal stability and porous properties of the experimental samples.