Correlation of compaction pressure, green density, pore size distribution and sintering temperature of a nano-crystalline 2Y-TZP-Al2O3 composite

Highly sinter-active nano crystalline composite powder of 2 mol% yttria doped tetragonal zirconia polycrystal (2Y-TZP) with 2 wt% alumina was synthesized by co-precipitation method. Crystallization temperature of the amorphous precursor powder, measured from simultaneous thermogravimetric (TG) and differential thermal analysis (DTA) techniques was found to be ∼470 °C. The powder was calcined at different temperatures in the range of 700-1000 °C. XRD patterns of the calcined powders revealed the presence of a single tetragonal phase. Particle size of the calcined powder measured by different techniques (X-ray line broadening, BET surface area and laser scattering technique) indicated an increase in the average particle size with calcination temperature. The study of compaction behaviour revealed the presence of soft agglomerates in the calcined powder. Pore size distribution of the green compacts obtained from a mercury porosimeter was found to be monomodal above a critical pressure. The onset temperature of sintering was found to increase with calcination temperature. Powders calcined at 800 °C and 900 °C had shown better sinterability at 1200 °C owing to the presence of finer pores with a narrow size distribution in the green compacts. Sintering behaviour of the powder calcined at 700 °C was found to be marginally poorer in comparison to the other samples, whereas the powder calcined at 800 °C had demonstrated best densification behaviour, especially when compacted at 300 MPa.