| Sintering Behaviour of Al2O3-ZrO2 Microcomposites Prepared by a Combined Gel-Precipitation Route |
S. Bhattacharyya, S. Bharati, S. K. Pratihar, R. K. Sinha, R. C. Behera and R. I. Ganguly
Pages : 18-21
DOI :10.1080/0371750X.2003.11012063 |
| Abstract |
| Al2O3-ZrO2 microcomposites having nominally equal volumes of the two phases were prepared by a combined gel-precipitation technique using AlCl3 and ZrOCl2 precursors. Dried gel powders were calcined at 375¢XC followed by compaction and sintering to study the (i) evolution of phases of Al2O3 and ZrO2 and (ii) densification behaviour of the microcomposites. ZrO2 crystallized to tetragonal / cubic structure formed at 375¢XC, while Al2O3 crystallized to ƒÔ-Al2O3 not before 1000¢XC and converted to ƒÑ-Al2O3 at or above 1200¢XC.
For sintering time of 4 h the density increased almost linearly from about 74% of the theoretical at 450¢XC to 94% at 1150¢XC and then gradually to a maximum of 97% at 1400¢XC. All the zirconia was in the tetragonal form up to 1000¢XC, but the tetragonal fraction decreases from 97% at 1100¢XC to 10% at 1400¢XC.
Sintering studies for varying holding times (4 h to 10 h) at temperatures from 1150¢X to 1250¢XC showed that the density increased, but the tetragonal fraction decreased with increasing temperature and with holding time at a given temperature. At 1200¢XC, the tetragonal fraction was 52% and the density was 97% of the theoretical. Scanning electron microscopy showed that the Al2O3 and ZrO2 phases were intimately mixed with average grain size of each phase less than 500 nm.
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