Abstract
ZrO 2 −γAl 2 O 3 gels were prepared by raising pH of colloidal sols from decomposing formamide. Two sintering barriers for these gels are those pores generated by θ–α phase transformation of γAl 2 O 3 and the grain growth inhibition of ZrO 2 that causes pore elimination more difficult. The barriers become prominent right after the phase change of γAl 2 O 3 . The effects of TiO 2 as sintering aid for γAl 2 O 3 involve (1) enhancing the phase transformation rate, (2) promoting grain growth and reducing the coordination number of pore, which consequently facilitate the pore elimination; and (3) elevating the shrinkage rate after γ-α transformation. The presence of ZrO 2 inhibits the grain growth of Al 2 O 3 , hence TiO 2 effects are retarded. Since most of TiO 2 is dissolved into ZrO 2 , TiO 2 influence is further reduced by ZrO 2 . The liquid phase occurring in CeO 2 −TiO 2 −ZrO 2 −Al 2 O 3 system enhances densification rate and grain growth of both ZrO 2 and Al 2 O 3 in sintering. The Finest microstructure is obtained via sintering 15vol% ZTA doped with 2wt% TiO 2 and 3mol% Y 2 O 3 at 1500°C.
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