Abstract
Highly transparent aluminas were synthesized by SPS processing under the conditions of 100 MPa and 200°C/min. High in-line transmittances of about 30 % at λ=400 nm and more than 60 % at λ=800 nm were obtained for the aluminas sintered at 1150°C for 10 min-45 min or at 1200 for 10 min. The in-line transmittance monotonously decreases with the increase of grain size in sintered aluminas and it is indicated that high transparency is attributed to both high densification and submicron grains less than 350 nm, which were realized by high heating rate of 200°C/min and high pressure of 100 MPa. Scarce existence of pores in SPSed aluminas was found by TEM observation and it is also responsible for their high in-line transmittance. Further, it is indicated that higher sintering temperature than 1200°C and longer sintering time, except for 1150°C, degrade the transparency of sintered aluminas.
