ABSTRACT
High density yttria doped tetragonal zirconia polycrystalline (3Y-TZP) ceramics with fine monomodal grain structure (grain size < 1 micron) have wide applications and immense potential as engineering materials. The components of this material are usually fabricated by cold-compaction of powder, followed by sintering in the temperature range 1200 - 1400°C in air.
In the present investigation, densification studies of green pellets of : (i) 3Y-TZP, (ii) 3Y-TZP with 10 volume percent alumina and (iii) 3Y-TZP with 0.25 mol percent cobalt oxide were carried out up to 1400°C using a high temperature dilatometer. The grain size and distribution of sintered pellets were evaluated by transmission and scanning electron microscopes.
Cobalt oxide was found to increase the shrinkage rate and improve the densification in the temperature range 850–900°C. The maximum shrinkage rate with cobalt oxide was found to be approximately 100 micron/minute at 1060°C (for 10mm long specimens). Alumina was found to retard the shrinkage rate. Two distinct shrinkage peaks were observed in the case of alumina-bearing 3Y-TZP. The maximum shrinkage rate was observed to be 50 micron/minute at 1000°C.
