Stabilization of transition alumina and grain growth inhibition in ultrafine Al2O3-5 wt.% SrO alloy

Nanocrystalline powders of pure alumina and alumina alloyed with 5 wt.% SrO were synthesized from aqueous nitrate solutions. The calcined powders were cold pressed and sintered in air at 1600 degrees C. X-ray diffraction (XRD ) has revealed nanocrystalline gamma-alumina both in pure and ahoy powders, with an average crystallite size of 3.5 and 7 nm, respectively. BET measur ements have indicated the specific surface area of 173 and 191 m(2)/g for t he as-crystallized pure and alumina alloy, respectively. These values decre ased to 10 and 29 m(2)/g after thermal cycling to 1250 degrees C. The nanoc rystalline alloy powder was stable up to 1350 degrees C compared to 1250 de grees C in the pure alumina. Alloying with 5 wt,% SrO increased the sinteri ng temperatures but also resulted in denser specimens with finer submicron grain sizes. (C) 2000 Elsevier Science B.V. All rights reserved.