Fabrication of Transparent Alumina by Rapid Vacuum Pressureless Sintering Technology.

Transparent alumina with high transmission has been first successfully prepared by rapid vacuum pressureless sintering processing at lower sintering temperature and reduced soaking time, compared with conventional pressureless sintering. The alumina sintered at 1670°C for 5 min has a residual porosity of 0.002% and a real in-line transmission of 64% for a wavelength of 1100 nm. We show that soaking time has an effect on the densification and transparency of alumina sintered at 1650°C. With increasing sintering temperature and soaking time, densification and grain growth occurred, and above 20 min, grain size increases slowly. The real in-line transmission of alumina increased with the densification and decreased with pore size growth. The light transmission and absorption were greatly affected by the grain size and pore defects. [ABSTRACT FROM AUTHOR]