With the aim of characterizing the effect of sintering temperature upon the transparency of zirconia, the optical properties and microstructure of translucent cubic zirconia which had been prepared by high-pressure spark plasma sintering at 1000 to 1200C were evaluated. Colour centers (oxygen vacancies with trapped electrons) and residual pores were primary defects in the samples. In spark plasma sintered samples, the total forward transmittance and in-line transmittance were affected mainly by colour centers with a limited contribution from residual pores; in contrast, the changes in reflectance were only related to the porosity. The amounts of colour centers and residual pores increase with sintering temperature that reduces the total forward and in-line transmittance of the as-sintered zirconia. Annealing in oxidizing atmosphere improves the total forward and in-line transmittance. During the annealing, the concentration of colour centers decreases but the porosity increases.

Effect of Sintering Temperature on Optical Properties and Microstructure of Translucent Zirconia Prepared by High-Pressure Spark Plasma Sintering. H.Zhang, B.N.Kim, K.Morita, H.Yoshida, K.Hiraga, Y.Sakka: Science and Technology of Advanced Materials, 2011, 12[5], 055003