Spark plasma sintering of transparent alumina

Transparent alumina with a fine grain size (0.27 μm) was obtained by controlling the heating rate during spark plasma sintering processing. The alumina sintered at 1150 °C with a heating rate of 8 °C/min has a residual porosity of 0.03% and an in-line transmission of 47% for a wavelength of 640 nm. We show that a low heating rate has an effect on the densification and transparency of alumina for sintering at 1150 °C.