Fabrication, microstructure and magneto-optical properties of Tb3Al5O12 transparent ceramics

Terbium aluminum garnet (Tb3Al5O12, TAG) transparent ceramics were fabricated by the solid-state reactive sintering of a mixture of commercial Tb4O7 and alpha-Al2O3 powders with tetraethoxysilane (TEOS) and MgO as sintering aids. Samples sintered at 1700 degrees C and 1725 degrees 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 degrees C has a pure garnet crystal structure, while the characteristic diffraction peaks of TAG disappear when sintered at 1725 degrees C. The sample sintered at 1725 degrees 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 degrees C exhibits homogeneous grains with the average size of about 5.97 mu m, however, no TAG grains are observed in the sample sintered at 1725 degrees C. The Verdet constants of the samples sintered at 1700 degrees C and 1725 degrees C are -179.4, -179.3 rad T-1 m(-1) at 633 nm, respectively. The thermal depolarization of the sample sintered at 1725 degrees C increases up to 2 x 10(-4) at maximum laser power of 91 W, which corresponds to the isolation ratio of 37 dB. (C) 2016 Elsevier B.V. All rights reserved.