Effect of Y substitution on the microstructure, magneto-optical, and thermal properties of (Tb1−xYx)3Al5O12 transparent ceramics

Faraday isolators can prevent the front-end system from disturbance and damage caused by a back-reflected beam, so they are important elements in laser systems. As magneto-optical materials are the most important component in Faraday isolators, the studies on magneto-optical materials have attracted much attention these years. Tb3Al5O12 (TAG) ceramics are considered to be one of the most promising magneto-optical materials for visible to near-infrared wavelength band application because of their outstanding comprehensive magneto-optical performance. However, the optical quality of TAG ceramics needs further optimization to meet the application requirements. In this work, high optical quality (Tb1−xYx)3Al5O12 (x = 0, 0.05, 0.1, 0.2, and 0.3) magneto-optical ceramics were fabricated successfully by solid-state reaction sintering combined with hot isostatic pressing (HIP) post-treatment. All the ceramics obtained showed a single garnet phase for different values of x in the range studied. The addition of Y2O3 was found to suppress the secondary phase and improve optical quality significantly. The ceramic samples obtained had clear grain boundaries and possessed the in-line transmittance values of 82.9% at 1064 nm and 82.2% at 633 nm, respectively. The Verdet constants of (Tb1−xYx)3Al5O12 ceramics with x = 0, 0.05, 0.1, 0.2, and 0.3 were −188.1, −175.4, −168.5, −143.0, and −119.9 rad/(T·m), respectively. The thermal conductivity of TAG ceramics was found to be 5.23 W/(m·K) at 25 ℃, and when 20% Y was substituted in place of Tb, the thermal conductivity decreased by only 9.4%.