Improved Edge-Defined Film-Fed Growth of Incongruent-Melting Tb₃Al₅O₁₂ Crystal with High Magneto-Optical and Thermal Performances

Abstract

Vis−NIR magneto-optical crystals are the key materials in the fields of optical fiber communication, smart grids, optical fiber lasers, and so on. In this paper, the incongruentmelting Tb 3 Al 5 O 12 (TAG) single crystals with centimeter size and high quality were grown rapidly by an EFG method with the suitable design of a melt component. The effects of the sintering temperature of polycrystalline materials, the melt component, and the growth rate on the crystal quality were discussed in detail. The Verdet constants, hardness, thermal expansion coefficients, specific heat capacities, and thermal diffusivities of TAG crystal were measured. The results show that the Verdet constant of the TAG crystal is 8−30% larger than those of Tb 3 Sc 2 Al 3 O 12 (TSAG) and Tb 3 Ga 5 O 12 (TGG) crystals. Additionally, the TAG crystal also has the advantage in both thermal conductivity and hardness. Therefore, the TAG crystal has good comprehensive performance and thus has important application prospects.

High Verdet Constant Materials for Magneto-Optical Faraday Rotation: A Review

“…Verdet constants of lanthanide glasses − (red square), diamagnetic ion glasses ,,− , (red circle), chalcogenide glasses − (red triangle), nanoparticle-glass composites − (red pentagon), garnet crystals ,− ,,− (green square), RE fluoride crystals − (green circle), other MO crystals − (green triangle), garnet-based ceramics − ,− (blue square), and sesquioxide-based ceramics − (blue circle) plotted to show general trends of peak Verdet constants of inorganic materials. The labels TSAG and TGG are terbium scandium aluminum garnet and terbium gallium garnet, respectively.…”

“…The general formula for naturally occurring garnets is X 3 Y 2 (SiO 4 ) 3 ; however, numerous synthetic garnets (such as those mentioned previously) with different metal oxide matrices have been developed which replace the Si atoms with Al, Ga, or Fe. These crystals are often prepared using traditional growth methods such as the Czochralski process or the Float Zone method to produce high quality materials. , The typical range of Verdet constants for these materials at room temperature in the visible and IR spectrum (400–1600 nm) are on the order of 10 4 °/T·m, ,− although Verdet constants as high as 10 5 °/T·m were achieved under cryogenic conditions (see Figure crystals). , RE fluoride crystals are a class of single crystal MO materials that possess Verdet constants similar to garnet crystals but are often optimized for high power laser systems. RE-fluoride crystals such as potassium terbium fluoride (KTF) are promising materials for multikilowatt average-power Faraday isolators, reporting peak Verdet constants of ∼6.50 × 10 3 °/T·m at 633 nm (Figure ).…”

Verdet Constant of Magneto-Active Materials Developed for High-Power Faraday Devices

“…One of the materials, which has been frequently co-investigated along with the TGG crystal ever since the 1960s, is the terbium aluminium garnet (TAG) crystal [56,63]. The main advantage of TAG is its ∼30% higher Verdet constant [56,90] and >50% higher thermal conductivity [91] as compared with the TGG. Nevertheless, TAG crystals are difficult to grow in dimensions suitable for practical applications because of their incongruent melting properties [90,92].…”

Tb3Al3Ga2O12: A Novel Visible–Infrared Faraday Crystal Exhibiting a Superior Magneto-Optical Performance

“…4 It is well-known that Tb transparency. 20 However, until now, only small-size TAG single crystals have been harvested through the edge-defined film-fed technique and hybrid laser floating zone method; 21 an industrially practicable TAG crystal cannot be obtained due to its incongruent melting nature. 22 With the purpose of making TAG melt congruently, the octahedral Al 3+ ions are replaced by Sc 3+ ions to stabilize the garnet phase, obtaining a Tb 3 Sc 2 Al 3 O 12 (TSAG) compound.…”

“…It is well-known that Tb 3 Al 5 O 12 (TAG) has been reported to show the best VIS–NIR magneto-optical properties, including a high Verdet constant (1.3 times TGG) and an excellent transparency . However, until now, only small-size TAG single crystals have been harvested through the edge-defined film-fed technique and hybrid laser floating zone method; an industrially practicable TAG crystal cannot be obtained due to its incongruent melting nature . With the purpose of making TAG melt congruently, the octahedral Al 3+ ions are replaced by Sc 3+ ions to stabilize the garnet phase, obtaining a Tb 3 Sc 2 Al 3 O 12 (TSAG) compound. , TSAG not only overcomes the growth difficulties of TAG but also preserves the excellent performance; the Verdet constant of TSAG is 1.25 times that of TGG. , Unfortunately, the growth of a homogeneous TSAG crystal is constrained by the nonuniform cation segregation .…”