Figure 1: Typical total forward transmittance and in-line transmittance spectra of the yttria stabilized tetragonal zirconia without (3Y) and with alumina dopant (3YE). These two specimens were sintered for 10 min at 1050°C under the pressure of 400 MPa by means of SPS. The post-SPS annealing was conducted at 900°C for 4 hours in air. The samples analyzed in Figures 2 to 5 were fabricated at the same conditions. The thickness of these two samples was 1 mm.