Fabrication of β- and β″-Al2O3 tubes by pressureless powder packing forming and salt infiltration

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A new forming method, pressureless powder packing (PLPP), was studied to fabricate the β- and β″-Al2O3 tubes. Alkali sources were infiltrated into the pores of α-Al2O3 tube preforms that had been prepared by the PLPP forming method. The composition for the synthesis of β″-Al2O3 phase was Na2O·0. 138Li2·4.4Al2O3. The β″-Al2O3 fraction of calcined and sintered bodies was increased with the increase of calcination temperature, and phase formation was largely affected by the type of starting α-Al2O3. Large particle size and narrow size distribution of fused α-Al2O3 resulted in uniform green microstructure that enhanced the homogeneity of alkali salts after infiltration, which was very important for the β″-Al2O3 formation. Sintered microstructure was uniform in all specimens but further development was required for density improvement.

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