MgAl2O4 spinel with transmittance approaching theoretical value at reduced sintering temperatures

Magnesium aluminate spinel is known to be a material with a good combination of mechanical properties, resistance against chemical attack and a high melting point, being thus a very promising material for application as a transparent material in harsh, high-temperature environments where glass fails. To improve the control over the microstructural evolution during sintering, Eu3+, Y3+ Mg2+ and their combinations were introduced as doping elements. The goal of the study was to optimize processing of fine spinel powder and investigate the potential for enhancing MgAl2O4 spinel density and in-line transmittance by using elements segregating to grain boundaries. The total and in-line transmittance were measured, and the characteristic pore size for transparent samples calculated based on the Rayleigh scattering approximation. Eu-doping proved to be effective in lowering the residual pore size and thus achieving in-line transmittance approaching the theoretical value at relatively low sintering temperatures (1400 °C).