A gradient film of Na-beta ''/beta-Al2O3 was designed and fabricated by a gas-solid reaction method on the alpha-Al2O3 substrate surface to improve the sealing performance of alpha-Al2O3/glass interface. Scanning electron microscope (SEM), X-ray diffraction (XRD) and electron probe microanalysis (EPMA) were applied to characterize the film. The experimental results showed that pre-treatment of the alpha-Al2O3 substrate surface with MgCO3 or NaOH promoted the formation of Na-beta ''/beta-Al2O3 film by generating intermediate phases of MgAl2O4 or sodium aluminum oxide. No obvious change was found from the film after 100 thermal cycles or heat treatment at 350 degrees C for 100 h, demonstrating its favorable thermal and chemical stability. (C) 2014 Elsevier B.V. All rights reserved.