Fabrication of high-strength transparent MgAl2O4 spinel polycrystals by optimizing spark-plasma-sintering conditions

By optimizing the heating rate during spark-plasma-sintering (SPS) processing, a high-strength transparent spinel (MgAl2O4) can be successfully fabricated for only a 20-min soak at 1300 degrees C. For the heating rates of <= 10 degrees C/min, the spinel exhibits an excellent combination of in-line transmission (50-70%), four-point-bending strength (>400 Mpa), and hardness (>15 GPa). The excellent optical and mechanical properties can be ascribed to the superimposed effects of the sub-micrograin size, fine-pore size, and low porosity, which are related closely to the heating rate during the SPS processing. The present study demonstrates that to attain a high-strength transparent spinel at low temperatures and short sintering times, the low-heating-rate SPS processing is more efficient compared with the high-heating-rate SPS processing.