In a significant breakthrough, material scientists from the Shanghai Institute of Ceramics, Chinese Academy of Sciences, have successfully fabricated high-quality (Tb1-xYx)3Al5O12 magneto-optical ceramics using Y2O3 as an additive. The research team, led by Jiang Li, vice director of the Transparent Ceramics Research Center, published their findings in the Journal of Advanced Ceramics on April 30, 2024.
Magneto-optical materials are crucial components in high-performance laser devices, particularly in Faraday isolators, which prevent front-end systems from disturbance and damage caused by back-reflected beams. Among the magneto-optical materials used in the visible to near-infrared wavelength band, Terbium Aluminum Garnet ceramics have shown great promise due to their high Verdet constant and good thermo-optic properties. However, the manufacturing process of TAG ceramics has been a challenge, as optical scattering from secondary phases, originating from the narrow solid-solution range, leads to optical loss.
To address this issue, the research team proposed the use of Y2O3 as an additive to increase the solid-solution range, suppress secondary phases, and improve the optical quality of TAG ceramics. The team fabricated (Tb1-xYx)3Al5O12 (x=0, 0.05, 0.1, 0.2, 0.3) ceramics using solid-state reaction sintering, followed by vacuum sintering combined with hot isostatic pressing post-treatment. They then investigated the crystal structure, microstructure, optical transmittance, Verdet constant, and thermal properties of the obtained ceramics in detail.
The results showed that Y2O3 significantly improved the optical transmittance of the ceramics by suppressing the secondary phase, likely due to the increase in solubility. The (Tb0.8Y0.2)3Al5O12 ceramics exhibited the highest in-line transmittance value of 82.9% at 1064 nm and 82.2% at 633 nm, with an optical loss nearly one order of magnitude lower than that of the obtained TAG ceramics in this work and the team's previous works.
However, the researchers also noted some side effects caused by Y substitution. The addition of Y2O3 reduced the Verdet constant of (Tb1-xYx)3Al5O12 ceramics, as Y3+ substitutes Tb3+, thereby directly reducing the concentration of paramagnetic ions. Furthermore, after adding 20 at.% Y, the thermal conductivity of the TAG ceramics decreased by 9.4%.
Despite these side effects, the research team considers Y2O3 to be a promising and effective additive for improving the quality of TAG ceramics for magneto-optical applications, as the optical loss directly affects the extinction ratio, insertion loss, change of beam quality, and many other performances for Faraday isolators.
In the future, the research team aims to further reduce the optical loss coefficient and fabricate (Tb1-xYx)3Al5O12 ceramics with larger aperture and thickness. This groundbreaking work by Jiang Li and his team at the Shanghai Institute of Ceramics, Chinese Academy of Sciences, has the potential to revolutionize the field of magneto-optical ceramics and enhance the performance of high-power laser devices.
