Impact of magnesium oxide concentration and yttrium-aluminum garnet stoichiometry deviation on the microstructure and optical transmission of YAG-based ceramics

The paper investigates the effect of the magnesium oxide concentration on the ceramics' microstructure and optical transmittance under conditions of excess Al3+ (4.8 mol.%) and Y3+ (2.9 mol.%) cations in the garnet structure, as well as the stoichiometric ratio Y3+/Al3+ = 3/5. Samples of optical ceramics were fabricated by vacuum sintering of compacts obtained from ceramic powders. Precursor powders with different ratios of Y3+/Al3+ cations were synthesized by the method of two-stage coprecipitation. Magnesium oxide was used as a sintering additive in concentrations from 0 to 0.2 wt.%. The microstructure and optical properties of the obtained samples were studied using scanning electron microscopy, energy dispersive X-ray spectroscopy and spectrophotometry techniques. It is shown that with the addition of magnesium oxide in a concentration of 0–0.2 wt.%, the stoichiometry of yttrium-aluminum garnet significantly affects ceramics' optical transmittance and microstructure. Samples of optical ceramics of yttrium-aluminum garnet with a light transmission coefficient of more than 70 % in the visible and near-infrared range were obtained.