c © TÜB_ITAK The Eect of Lanthanum and Barium Additives on the Thermal Stabilization of γ-Al2O3

The eect of La and Ba additives on the thermal stabilization of γ-Al2O3 was investigated through total-surface-area measurements. The parameters considered were additive content, calcination temper-ature, and calcination period. The eect of precalcination was also studied. It was found that thermal stabilization caused by 3 wt % La and Ba is superior to 6 wt % La or Ba, and the positive eect of 3 wt % La and 3 wt % Ba are almost identical. The nearly threefold increase in the total surface area of 3 wt % La or Ba doped samples calcined above the γ − phase-transition temperature indicates that the aluminate complexes formed with La or Ba during phase transition impart thermal resistance to sintering. Aluminate formation at these temperatures is veried by XRD measurements. Precalcination at 723 K stabilizes the γ-Al2 O3 structure, leading to higher surface areas in the undoped sample upon sintering