Optimization of magnesia sintering parameters fabricated by spark plasma sintering method for infrared transparency

Abstract

In this study, sintering of magnesia nanopowder was investigated using spark plasma sintering (SPS), and the effects of time and pressure on microstructure, physical properties, density, and infrared transparency were studied. Densification of magnesia nanopowder was examined at 1100 °C and the pressure of 40, 60, and 80 MPa, and at different times. Findings indicated that MgO ceramics’ density rapidly increased with increasing the sintering time up to 5 min, while it increased with a slow speed after 5 min. Analysis of grain growth rate at different times indicated that, in the initial stages of sintering, the process was done through a non-diffusional process and, in the final 15 min of the process, it was done through lattice diffusion. In addition, examining the yield stress of the sintered sample at 1100 °C and considering its conformity with the results of theoretical density showed that it underwent plastic deformation up to 15 min. In general, the results revealed that the main mechanism of magnesia sintering was plastic deformation. The highest infrared transmittance of 65% was obtained for the sample sintered at 1100 °C for 20 min at 80 MPa.