Abstract: Two factors which influence the measurement of particle size distribution were discussed. Selecting proper ultrasonic time can decrease the agglomeration of
powders and lower the average particle size. Three kinds of nano-size Y-TZP powders require different amounts of dispersant to achieve lowest particle
size. The optimum amount of dispersant for TZP1, TZP2 and TZP3 is 1.186%, 1.186% and 0.237% respectively. No significant improvement in the degree of dispersion
was observed when the amount of dispersant exceeded the optimum value. The adsorbed polyelectrolyte results in a significant zeta potential on the particles and sterically
prevents the particles from flocculating, leading to colloid stability increased. The pH of suspension is near to weakly basic (pH=8.0) if NH4PAA is added even as little as 0.237%.

Key words: nano zirconia powder, particle size distribution, Zeta potential