Transparent mullite ceramic from single-phase gel by Spark Plasma Sintering

摘要

Monophasic mullite precursors with composition of 3 Al_2O_3 centre dot 2SiO_2 (3:2) were synthesized and then were sintered by Spark Plasma Sintering (SPS) to form transparent mullite ceramics. The precursor powders were calcined at 1100 deg C for 2 h. The sintering was carried out by heating the sample to 1450 deg C, holding for 10 min. The sintered body obtained a relative bulk density of above 97.5 percent and an infrared transmittance of 75-82 percent in wavelength of 2.5-4.3 mu m without any additive. When the precursor powders were calcined at below 1100 deg C, it was unfavorable for completely eliminating the residual OH, H_2O and organic compound. However, when calcined temperature was too high, it was unfavorable either for full densification due to the absence of viscous flow of amorphous phase. At the same calcined temperature, the transmittance of sintered body was decreased with the increase of the sintering temperature above 1450 deg C owing to the elongated grain growth.