Effect of (Tb+Y)/Al ratio on Microstructure Evolution and Densification Process of (Tb0.6Y0.4)₃Al₅O12 Transparent Ceramics.

Zhong Wan,Dewen Wang,Shiwei Wang,Junping Wang,Yinzhen Wang,Dan Han,Jian Zhang

doi:10.3390/ma12020300

Abstract

(Tb0.6Y0.4)3Al5O12 transparent ceramics were successfully fabricated by solid-state reactive sintering using Tb4O7, Y2O3, and α-Al2O3 powders as raw materials. The effect of (Tb+Y)/Al ratio on microstructure evolution and densification process was investigated in detailed. The results showed that the grain growth kinetics were significantly affected by (Tb+Y)/Al ratio. Al-rich and Tb-rich phases appeared in part of the samples of different ratios. Particularly, excess aluminum increased the diffusing process, leading to a higher densification rate, while samples with excess terbium ratios displayed a smaller grain size and lower relative density. The optical quality was highly related to the amount of the secondary phase produced by different (Tb+Y)/Al ratios. Finally, (Tb0.6Y0.4)3Al5O12 transparent ceramics have been fabricated through pre-sintering in vacuum, followed by hot isostatic sintering (HIP), and the best transmittance of sample with a 4 mm thickness was approximately 78% at 1064 nm.

Highlights

Magneto-optical material, including glass, single crystal, and transparent ceramic, is the crucial constitution of the optical isolators in high-power laser systems [1,2,3]
Liu et al [19] investigated that a small excess of yttrium was tolerable for the optical quality of ceramics compared with excess alumina
The phase compositions of pre-sintering plates were identified by X-ray diffraction (XRD; D2, Bruker, Hamburg, Germany) with

Summary

Introduction

Magneto-optical material, including glass, single crystal, and transparent ceramic, is the crucial constitution of the optical isolators in high-power laser systems [1,2,3]. Compared to TGG, Tb3 Al5 O12 (TAG) has a higher Verdet constant, which makes it a highly sought magneto-optical isolator material for future applications [7]. Many efforts have been devoted to solving this problem, the size of crystals is still too limited to meet the requirement of practical application [11,12] This phenomenon can be effectively avoided by fabricating TAG transparent ceramic below the phase transition point, thanks to the cubic structure. Liu et al [19] investigated that a small excess of yttrium was tolerable for the optical quality of ceramics compared with excess alumina They deduced that the average grain size abruptly decreased, and the porosity increased with the increasing of both excess Al2 O3 and Y2 O3. The effect of (Tb+Y)/Al ratio on the phase formation, densification process, and microstructure evolution was elaborately investigated

Experimental Procedure

Characterization

Phase Formation Process

Densification

Transmittances ofofdifferent ratios pre-sintered

Conclusions