Effects of organic binders on the sintering of isostatically compacted zirconia powders

Abstract

Certain processing-related flaws in cold isostatically pressed ceramic powder compacts may arise from the delayed burn-out of organic binders until the sintering temperature is approached, although the isostatic compaction technique usually gives a higher and much more uniform green density than the conventional die compaction technique. For the 3 mol% Y₂O₃-doped zirconia powder in which 3 wt% PEG 1500 was introduced, the sintered density and sintering shrinkage were found to decrease in a near linear manner with increasing isostatic compaction pressure. The processing-related defects were identified as intergranular pores (1–5 μm). It is considered that these processing-related defects are a consequence of incomplete organic burn-out at low and intermediate temperatures in the heating-up period and the swelling of intergranular pores associated with the burn-out of residual organic binders at temperatures close to the sintering temperature. A higher calcination temperature and an extended calcination dwell time may be required to eliminate the organic residuals in the isostatically pressed ceramic powder compacts than in the conventional die-pressed samples.