Effect of Sc substitution on the phase composition, microstructure, and properties of (Tb_1−xSc_x)₃(Al_1−ySc_y)₂Al₃O₁₂ transparent ceramics

Terbium aluminum garnet (Tb₃Al₅O₁₂, TAG) ceramics are one of the most promising magneto-optical materials owing to the outstanding comprehensive performance. Many works are focusing on the improvement of optical quality of the TAG ceramics in these years. A key point of improving the optical quality is ensuring the accuracy of the stoichiometric ratio and avoiding the secondary phases. In this work, 0, 2, 4, and 6wt.% Sc₂O₃ are added in the TAG ceramics for increasing the solid solubility. The effect of Sc substitution on the crystal structure, sintering process, microstructure, optical transmittance, and magneto-optical property of the (Tb_1-xSc_x)₃(Al_1-ySc_y)₂Al₃O₁₂ (TSAG) ceramics is studied in detail. 4wt.%Sc₂O₃:TAG ceramics with an in-line transmittance of 82.2% at 1064 nm and 81.2% at 633 nm are fabricated successfully, and the Verdet constant is 164.4 rad·T^-1·m^-1 at 633 nm. Antisite defects (ADs) and Sc replacement in TAG are further studied by first-principles calculations to figure out the working mechanism of Sc. Both experimental and calculation results show that the introduction of Sc can effectively increase the solid solubility of TAG ceramics, suppress the secondary phases, and hence improve the optical transmittance.