The transparent ceramics research group of the SHGJ Institute of Precision Optics has made new progress in the research of terbium aluminum garnet-based magneto-optical ceramics. It has prepared ZrO2 as a high-quality Terbium aluminum garnet (Tb3Al5O12, TAG) for the first time transparent ceramics, its linear transmittance at 1064nm reaches 82.04%, reaching the domestic leading and international advanced level, the field constant at 632.8nm is ~ 175 rad / T / m, higher than the current commercial terbium gallium garnet (TGG) about 30%. Related achievements have been published in Scripta Materialia.
Terbium aluminum garnet (Tb3Al5O12, TAG) transparent ceramics has important application prospects in high-power Faraday magneto-optical isolators because of its excellent magneto-optical performance, high thermal conductivity, and high laser damage threshold. However, during the preparation of transparent ceramics, it is very easy to form closed pores, residual impurities and equal scattering sources of grain boundaries, resulting in severe heat absorption effects under high-power laser radiation, resulting in greatly reduced device isolation or even damage to the device or laser system. Terbium aluminum garnet (Tb3Al5O12, TAG) transparent ceramics The improvement of optical quality and the elimination of scattering centers are the focus of the current research on terbium aluminum garnet based magneto-optical ceramics. The research team broke through the routine, and by introducing ZrO2 as a sintering aid, on the basis of optimizing the heating and heat preservation mechanism in vacuum sintering, a Zr: TAG magnetic with extremely large grains (~ 400um) and high optical transmittance was obtained Light ceramics.
In this study, a systematic study of the effect of ZrO2 on TAG grain growth and phase composition changes at different sintering stages was carried out. It was found that on the one hand, ZrO2 can promote the densification of ceramics at a low temperature stage, which is conducive to the elimination of pores; on the other hand, the grain growth is significantly accelerated in the late sintering above 1550 ℃, and through X-ray diffraction (XRD) and X-ray photoelectron energy XPS found that ZrO2 appeared on the surface of the sample and was eliminated after polishing. Studies have shown that ZrO2 as a sintering aid can promote sintering in the middle and early sintering, and be discharged from the ceramic system at the end of sintering, avoiding the increase in scattering caused by residues in the grain boundary, so the optical quality of transparent ceramics can be further improved.
SHGJ successfully prepared Terbium aluminum garnet (Tb3Al5O12, TAG) transparent ceramics for the first time since 2011. The project team is conducting research work on performance and production process optimization.
Terbium aluminum garnet (Tb3Al5O12, TAG) transparent ceramics were fabricated by the solid-state reactive sintering of a mixture of commercial Tb4O7 and α-Al2O3 powders with tetraethoxysilane (TEOS) and MgO as sintering aids. Samples sintered at 1700 ° C and 1725 ° C for 20 h were utilized to examine the phase compositions, optical quality, microstructure and magneto-optical property. X-ray diffraction (XRD) results show that the sample sintered at 1700 ° C has a pure garnet crystal structure, while the characteristic diffraction peaks of TAG disappear when sintered at 1725 ° C. The sample sintered at 1725 ° C shows high transparency and the optical transmittance is beyond 80% in the region of 600–1500 nm. It is found that the sample sintered at 1700 ° C exhibits homogeneous grains with the average size of about 5.97 μm, however, no TAG grains are observed in the sample sintered at 1725 ° C. The Verdet constants of the samples sintered at 1700 ° C and 1725 ° C are −179.4, −179. 3 rad T−1 m−1 at 633 nm, respectively. The thermal depolarization of the sample sintered at 1725 ° C increases up to 2 × 10−4 at maximum laser power of 91 W, which corresponds to the isolation ratio of 37 dB .