Transparent nanometric cubic and tetragonal zirconia obtained by high-pressure pulsed electric current sintering

Transparent samples of cubic (8 mol % yttria) and tetragonal (3 mol % yttria) zirconia were prepared from nanometric powders by the pulsed electric current sintering process. The crystallite size of the resulting dense samples was about 50 nm in both cases. The consolidation pressure had a positive effect on the occurrence of transparency for both modifications. Transmittance in the near infrared for 1 mm thick samples is above the 60 % for the cubic (8 %YSZ) and above 50% for the tetragonal (3 % YSZ) zirconia, representing between 70 and 80 % of the theoretical values of the two modifications Samples had a yellowishbrown coloration which was attributed to the presence of color centers. Annealing in oxygen improved transmittance initially, but prolonged annealing resulted in translucent samples. The role of porosity in transmittance is analyzed.