A new forming method, pressureless powder packing (PLPP), was studied to fabricate the beta- and beta "-Al2O3 tubes. Alkali sources were infiltrated into the pores of alpha-Al2O3 tube preforms that had been prepared by the PLPP forming method. The composition for the synthesis of beta "-Al2O3 phase was Na2O . 0.138Li(2)O . 4.4Al(2)O(3). The beta "-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 alpha-Al2O3 Large particle size and narrow size distribution of fused alpha-Al2O3 resulted in uniform green microstructure that enhanced the homogeneity of alkali salts after infiltration, which was very important for the beta "-Al2O3 formation. Sintered microstructure was uniform in ail specimens but further development was required for density improvement. (C) 1998 Kluwer Academic Publishers. [References: 21]
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