Effect of non-stoichiometric Ga content on the microstructure and optical transparency of terbium gallium garnet ceramics

The use of Faraday isolators in high-power lasers is currently a high-priority research topic and terbium gallium garnet (Tb 3 Ga 5 O 12 , TGG) transparent ceramic is a magneto-optical material with great potential for applications in the visible and near-infrared ranges. In this paper, the effect of chemical composition adjustment on the microstructure and properties of Tb 3 Ga 5(1+x) O 12 ceramics (where x is the non-stoichiometric index corresponding to the percentage difference in the amount of Ga used in the synthesis with respect to its content in the stoichiometric compound) was investigated. Powders obtained from starting materials of different stoichiometry were found to have similar morphology. However, the relative densities of the ceramics after pre-sintering in air increase with increasing Ga content. After the HIP post-treatment, the optimal properties with an in-line transmittance of 78.5 % (1.5 mm thick) at 1064 nm, and the Verdet constant of the ceramics with x = 0.8 % reaches −134.1 rad T −1  m −1 at 633 nm.