Transparent MgAl2O4 spinel fabricated by spark plasma sintering from commercial powders

Three different MgAl2O4 spinel powders (S25CRX12, S25CRX14 and S30CR) supplied by Baikowski company were sintered by Spark Plasma Sintering and optically characterized for their transparency. The real in-line transmission (RIT), total forward transmission (TFT), total reflection (TR) and diffuse reflection (DR) were measured for all powders sintered between 1250 and 1350 degrees C with an incremental step of 20 degrees C. The S25CRX12 powder sintered at T = 1350 degrees C exhibits the highest RIT (83.6%) at the wavelength of 550 nm which was enhanced by a post-annealing at 1200 degrees C up to similar to 85%. The TR and DR of the S30CR sample appear to be independent of wavelength and sintering temperature. The TR is around 11% whereas the DR remains insignificant (1-2%). For the two powders S25CRX12 and S25CRX14, the TR and DR vary according to the wavelength and depend substantially on the sintering temperature. Above 1310 degrees C, the TR and DR remain almost constant (TR approximate to 12% and DR approximate to 1-4%) in the examined wavelength range.