Terbium Aluminum Garnet Research Articles

Fine-Grained Tb3Al5O12 Transparent Ceramics Prepared by Co-Precipitation Synthesis and Two-Step Sintering

In recent years, transparent terbium aluminum garnet (TAG) ceramics have attracted much attention for use in high-power Faraday isolators. Fine-grained ceramics usually possess better mechanical properties and accordingly better service performance. In this work, transparent TAG ceramics with fine grains were prepared using a two-step sintering procedure based on the low-temperature sintering process to suppress grain growth. The composition of TAG precursor and powders calcined at different temperatures was studied in detail. The microstructure and relative density of air pre-sintered TAG ceramics were studied to meet the requirements of hot isostatic pressing (HIP) post-treatment. Driven by the low pre-sintering temperature in air, the average grain sizes of the obtained TAG ceramics after HIP treatment are about 2.9–5.3 μm. The TAG ceramics (1.2 mm thick) pre-sintered at 1450 °C with HIP post-treatment at 1550 °C for 3 h under a 176 MPa Ar atmosphere possess the highest in-line transmittance of 80.3% at 1064 nm. The Verdet constant of the TAG ceramics at 632.8 nm is −180.5 rad·T−1·m−1 at room temperature, which is about 1.3 times larger than that of the commercial Tb3Ga5O12 single crystals.

Fabrication and characterizations of Tb3Al5O12‐based magneto‐optical ceramics

AbstractTransparent terbium aluminum garnet (TAG)‐based ceramics were fabricated by vacuum pre‐sintering and hot isostatic pressing (HIP) posttreatment from the co‐precipitated TAG powders with different stoichiometric ratios. After component optimization, the transparent ceramics with TAG single‐phase and attractive optical quality were obtained. The in‐line transmittance of optimal Tb(1+x)3(Al0.996255Si0.003745)5O12.0093625+3x/2 (x = −.004, −.002) ceramics (1.7‐mm thick) pre‐sintered at 1700°C for 20 h with HIP posttreatment at 1700°C for 3 h under 176‐MPa Ar reaches 82.6% at the wavelength of 1064 nm. With increasing terbium components, the secondary phase TAP appears in ceramics, which significantly degrades the optical quality of TAG‐based ceramics. The Verdet constant of the TAG‐based ceramics at 632.8 nm is about −181 rad T−1 m−1 at room temperature, which is about 33% higher than that of the TGG single crystals (−134 rad T−1 m−1).

Photo-induced preparation of Ce-doped terbium aluminum garnet and its luminescent properties

Ce(III) activated terbium aluminum garnet (Tb3Al5O12:Ce, TAG:Ce) powder as a luminescent phosphor was synthesized by the photo-induced method. The irradiation of an aqueous solution containing formate anions and soluble salts of both metal ions by UV light led to the precipitation of an amorphous solid phase. Subsequent heat treatment at 1200 °C resulted in the crystallization of the TAG:Ce phase-pure garnet structure. The structure and morphology of the products were investigated by X-ray powder diffraction (XRPD) and by scanning electron microscopy (SEM). The particle size, evaluated by transmission electron microscopy (TEM), ranges from 50 to 150 nm. The manufactured Ce-doped TAG features intensive luminescence corresponding to Ce(III) 5d–4f transitions at 559 nm. Due to its high density, chemical stability, non-toxic character, and excellent scintillation efficiency, the application of Ce-doped TAG nano-powder in photodynamic therapy and preparation of optical ceramics was suggested.

Down conversions excitation dependent luminescent properties of Terbium Aluminum Garnet

TAG (terbium aluminum garnet, (Tb3Al5O12) is being investigated recently for their applications in the realization of photonic devices because of its broad transmission ranging from 350 to 1500nm. An emission property of any material depends upon electronic transition levels, temperature, excitation wavelength etc. A lot of research had been reported on temperature dependent emission properties of TAG. In this study an attempt had been made to explore the excitation dependent emission properties of TAG. TAG was prepared by sol gel technique followed by sintering at 1100°C. Structural phase was analysis from the XRD spectra. XRD studies confirmed the formation of nano material and has cubic structure. The emission properties were studied by exciting the TAG by UV light and blue light i.e. 280nm, 300nm, 380 nm, 400nm, 480 and 484nm. Spectra power distribution curve was obtained from emission data excited by with UV radiation and blue light. From emission spectra, Colour co-ordinates (CIE), colour correlated temperature (CCT) and colour purity were calculated for TAG at different excitation. Emission properties indicates that TAG is potential nanophosphor for optical devices.

Progress in Transparent Nano-Ceramics and Their Potential Applications.

Transparent nano-ceramics have an important high-transmittance, material-integrating structure and function and a variety of potential applications, such as use in infrared windows, optical isolators, composite armors, intelligent terminal screens, and key materials of solid-state lasers. Transparent ceramics were originally developed to replace single crystals because of their low fabricating cost, controllable shape, and variable composition. Therefore, this study reviews and summarizes the development trends in transparent nano-ceramics and their potential applications. First, we review the research progress and application of laser nano-ceramic materials, focusing on the influence of controllable doping of rare earth ions on thermal conductivity and the realization of large-scale fabrication technology. Second, the latest research progress on magneto-optical transparent nano-ceramics, mainly including terbium gallium garnet (Tb3Ga5O12, TGG) ceramics and terbium aluminum garnet (Tb3Al5O12, TAG) ceramics, are summarized, and their performance is compared. Third, the research progress of transparent armor nano-ceramic materials, represented by MgAl2O3 and Aluminum oxynitride (AlON), are reviewed. Lastly, the progress in electro-optical transparent nano-ceramics and scintillation transparent nano-ceramics is reported, and the influence of the material-fabrication process on electro-optic effect or luminous intensity is compared. Moreover, the effect of particle diameter on fabrication, the relationship between nano powder and performance, and different sintering methods are discussed. In summary, this study provides a meaningful reference for low-cost and sustainable production in the future.

Sintering parameter optimization of Tb3Al5O12 magneto‐optical ceramics by vacuum sintering and HIP post‐treatment

AbstractTransparent terbium aluminum garnet (TAG) ceramics were achieved by the vacuum sintering plus HIP post‐treating from the coprecipitated TAG nanoparticles. The influences of vacuum sintering temperature and sintering aid TEOS on the optical quality of the TAG ceramics were studied. The results show that with the increase of sintering temperature, the optical quality of TAG ceramics is improved gradually, and the in‐line transmittance of the TAG ceramics treated at 1720°C for 20 hours under vacuum and then HIP post‐treated at 1700°C for 3 hours under 200 MPa argon gas is 81.6% at 1064 nm. The sintering additive TEOS can improve the optical quality of TAG ceramics and inhibit the valence state change of Tb3+ ions to Tb4+ during the annealing process. The Verdet constant of the TAG ceramics at 632.8 nm is about −178 rad·T−1·m−1 at room temperature, which is 1.3 times that of the commercial TGG crystals (−134 rad·T−1·m−1).

Properties of TAG ceramics at room and cryogenic temperatures and performance estimations as a Faraday isolator

We investigated material properties of terbium aluminum garnet (TAG) ceramics and its characteristics as a material for a Faraday isolator for high-average power lasers. We measured the transmittance, absorption coefficient, and temperature dependencies of Verdet constant and thermal conductivity. Consequently, our model analysis shows that TAG ceramic isolators can be operated over 3 kW average laser power at a 30 dB isolation ratio. The power limit becomes higher if a gas cooling scheme is applied.

Excitation dependent emission of terbium aluminium garnet doped with gadolinium

This study reports the emission (400-700nm) properties of Gd (0.1, 0.5, 1.0 mol%) doped TAG nanophosphor synthesized by sol gel technique. Powder XRD spectra of doped TAG were indexed using JCPDS file No. 17-0735 implying that the basic structure of TAG remained unchanged on doping. The emission was excited with 280, 380 and 460nm radiation from a Xe lamp. The spectral features of the emission spectra were almost independent of both the doping as well as the excitation radiation. However, Gd concentration dependent variations in the emission intensity were observed. The observed emission intensity was maximum in TAG doped with 0.5mol% Gd while quenching was observed at 1.0mol% concentration level. This concentration dependent intensity variation which also depended on the wavelength of the excitation radiation could be due to energy exchange between Gd and Tb ions.

Fabrication and characterization of Tb3Al5O12 magneto-optical ceramics by solid-state reactive sintering

Terbium aluminum garnet (TAG) transparent ceramics were fabricated by solid-state reactive sintering in vacuum combined with hot isostatic pressing (HIP) post-treatment using tetraethoxysilane (TEOS) as sintering aid. The influences of TEOS amount on the densification, microstructure and optical properties of TAG ceramics were investigated. The in-line transmittance of the TAG ceramic with 0.2 wt% TEOS additive, which was fabricated by pre-sintering at 1700 °C for 20 h and HIP post-treating at 1700 °C for 3 h, can reach about 66% in the visible and near-infrared regions. With appropriate amount of sintering aid, the transmittance of TAG ceramics in the visible wavelength range can be improved significantly by prolonging the holding time.

Fabrication and characterizations of holmium oxide based magneto-optical ceramics

A significant improvement in the sintering of Ho2O3 powders obtained by self-propagating high-temperature synthesis as a result of the addition of lanthanum oxide was made. It was found that the addition of 5% lanthanum oxide slightly affects the Verdet constant value (which is ~1.3 times higher than the corresponding value for terbium-gallium garnet, and is similar to the value for terbium-aluminum garnet ceramics), but significantly increases the transparency of ceramics. Samples of 5% La:Ho2O3 magneto-optical ceramics with a transmission of up to 76% at a wavelength of 1 μm at a thickness of 1 mm were obtained. Such La:Ho2O3 ceramics have transparency windows in the ranges of 0.93–1.06, 1.3–1.6 and 2.2–7 μm, what distinguishes them from materials containing Tb3+ ions, that are opaque in these ranges. It is shown that La:Ho2O3 ceramics have relatively high mechanical characteristics (HV = 8.4 GPa, E = 182 GPa, KIC = 0.95 MPa m0.5) which vary slightly depending on the lanthanum oxide concentration.

Characterizations of REE:Tb2O3 Magneto‐Optical Ceramics

The magneto‐optical ceramics of terbium oxide doped with different rare earth elements (REE) REE:Tb2O3 (REE—Y3+, Lu3+, Sc3+, Ce3+, Dy3+, Ho3+, Yb3+, Nd3+) are successfully fabricated by hot pressing using powders obtained by the self‐propagating high‐temperature synthesis (SHS) method. The prepared REE:Tb2O3 ceramics have good optical quality and magneto‐optical properties. The in‐line transmittance of Tb2O3 ceramics doped with REE except Sc3+ is close to undoped terbium oxide, especially in the long‐wavelength region. The Verdet constant of the REE:Tb2O3 samples considered at 633 nm is about 3.3 and 2.6 times higher in absolute value than that of the commercial terbium–gallium garnet (TGG) single crystal and terbium–aluminum garnet (TAG) ceramics, respectively. It is noted that REE (except Yb3+ and Nd3+) doping only slightly increases the Verdet constant of pure Tb2O3 (when the content of terbium ions in the optical element is taken into consideration in the calculation). The dilution of the Tb2O3 matrix with REE in relatively high concentrations leads to a decrease in the absolute value of the Verdet constant.

Optical properties of TAG co-doped with Ce and Eu

Nanopowder samples of terbium aluminum garnet (TAG) doped with Ce and Eu were prepared by a sol–gel technique followed by sintering in air at various temperatures (maximum of \(1100{^{\circ }}\hbox {C}\)). The investigated concentrations of both the dopants were 0.1, 0.5 and 1.0 mol%. Nine powder samples prepared by the permutation of the doping concentrations were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX), powder X-ray diffraction (XRD) and optical spectroscopic techniques. SEM and TEM investigations confirmed the nano-structure of the prepared powders while EDX not only confirmed the doping of Ce and Eu in TAG but also eliminated the possibility of any interfering impurities. Powder XRD showed that the basic structure of TAG did not change on doping which was further confirmed by Fourier-transform infrared studies. However, optical absorption and Raman scattering investigations showed the distortion of the TAG lattice on doping. Emission (photoluminescence) in the spectral region of 400–700 nm was observed when excited by 280 nm radiation. The intensity of this emission showed interesting dopant concentration dependence. The emission from TAG co-doped with 0.5 mol% of both Ce and Eu is of particular interest as its calculated colour chromaticity coordinates ‘x and y’ were found as \(x = 0.35\) and \(y = 0.35\) which are very close to that of sun light at noon indicating its potential as a material for the white light source.

Fabrication and characterizations of (Tb1-xPrx)3Al5O12 magneto-optical ceramics for Faraday isolators

Praseodymium doped terbium aluminum garnet (Pr:TAG) magneto-optical ceramics with different doping concentrations were fabricated by vacuum pre-sintering and hot isostatic pressing (HIP) post-treatment from the co-precipitated Pr:TAG nanopowders. It is found that all the as-synthesized powders exhibit a pure TAG phase and show good dispersity. The in-line transmittance of Pr:TAG ceramics fabricated by pre-sintering at 1700 °C for 20 h and HIP post-treating at 1700 °C for 3 h decreases from 80.6% to 76.3% at 1064 nm with the Pr3+ doping concentration increasing from 0 at% to 2.0 at%. The Verdet constant of the 2.0 at% Pr:TAG ceramics at 633 nm is −189.8 rad T-1 m-1, which is 42% larger than that of the commercial TGG single crystals (−134 rad T-1 m-1). The superior characteristics of the Pr:TAG ceramics indicate that they have great potential to meet the increasing requirements for magneto-optical devices used in the visible and near-infrared wavelength.

Study of different magneto-optic materials for current sensing applications

Abstract. This article discusses the properties of different diamagnetic and paramagnetic materials for a basic current/magnetic field sensor system set up with different relative orientations of analyzers and polarizers. The paper analyzes linearity ranges of different materials and their sensitivity for different wavelengths. Terbium doped glass (TDG), terbium gallium garnet (TGG), doped TGG and dense flint glass materials are used for analysis based on Faraday's rotation principle. TGG shows high Faraday rotation, temperature stability and high optical quality. Three ranges of the magnetic field have been chosen for performance analysis. The study reveals that doping of praseodymium (Pr3+) on TGG exhibits a better response at 532 nm as well as 1064 nm wavelengths than TGG. At 632.8 nm wavelength, cerium (Ce3+) doped terbium aluminum garnet (TAG) ceramic exhibits better resolution than others. The study has been done for performance analysis of different MO sensors applicable for measurement of various process parameters like current, displacement, and magnetic field.

Fabrication and properties of (Tb1-xCex)3Al5O12 magneto-optical ceramics with different doping concentrations

Cerium doped terbium aluminum garnet (Ce:TAG) magneto-optical ceramics with different doping concentrations were fabricated using the co-precipitated powders. All the as-synthesized powders exhibit a pure TAG phase and show good dispersity. Highly transparent Ce:TAG ceramics were then successfully fabricated by pre-sintering at 1650 °C for 20 h and HIP post-treating at 1700 °C for 3 h. The 0.5at% Ce:TAG ceramic shows the best transparency, and its transmittance is ~80% in the 600–1500 nm range. The Vertdet constant at 633 nm of the 2.0at% Ce:TAG ceramics is −196.2 rad T−1 m−1, which is 46% larger than that of the commercial TGG single crystals.

Highly transparent Tb3Al5O12 magneto-optical ceramics sintered from co-precipitated powders with sintering aids

Highly transparent terbium aluminum garnet (Tb3Al5O12, TAG) magneto-optical ceramics were fabricated from co-precipitated nanopowders with tetraethoxysilane (TEOS) as sintering aid by vacuum sintering combined with hot isostatic pressing (HIP) post-treatment. The ball milled TAG powder shows better dispersity than the as-synthesized powder, and its average particle size is about 80 nm. For the ceramic sample pre-sintered at 1720 °C for 20 h with HIP post-treated at 1700 °C for 3 h, the in-line transmittance exceeds 76% in the region of 400–1580nm (except the absorption band), reaching a maximum value of 81.8% at the wavelength of 1390 nm. The microstructure of the TAG ceramic is homogeneous and its average grain size is approximately 19.7 μm. The Verdet constant of the sample is calculated to be −182.7 rad·T−1·m−1 at room temperature.

The temperature dependence of thermooptical properties of magnetooptical TAG ceramics doped with silicon and titanium

Thermal effects in terbium aluminum garnet (TAG) ceramics (thermal lens and thermally induced depolarization) doped with silicon and titanium were investigated in temperature range of 79–293К. Samples with low dopant concentrations shows decreasing of negative thermal effects with cooling to 79 K. However for most part of samples thermal depolarization starts increasing after initial decreasing with cooling. Apparently it is connected with defects in media.Best sample (0.4 at% of Si) as pure TAG shows monotonous decreasing of thermally induced depolarization and 3.5 times Verdet constant increasing with cooling to 79 K, that leads to 1.8-times advantage over common magnetooptical media – terbium gallium garnet. It allows to provide an isolation of 30 dB at a radiation power of more than 6 kW as estimated. However, the procedure for creating ceramics samples obviously needs improvement because of the large scatter in the quality of the samples.

Structural and luminescence properties of yellow phosphors prepared by a modified sol-gel method

Abstract

Fabrication of Tb3Al5O12 transparent ceramics using co-precipitated nanopowders

Terbium aluminum garnet (TAG) precursor was synthesized by a co-precipitation method from a mixed solution of terbium and aluminum nitrates using ammonium hydrogen carbonate (AHC) as the precipitant. The powders calcined at different temperatures were investigated by XRD, FTIR and FESEM in order to choose the optimal calcination temperature. Fine and low-agglomerated TAG powders with average particle size of 88 nm were obtained by calcining the precursor at 1100 °C for 4 h. Using this powder as starting material, TAG transparent ceramics were fabricated by vacuum sintering combined with hot isostatic pressing (HIP) sintering. For the sample pre-sintered at 1700 °C for 20 h with HIP post-treated at 1700 °C for 3 h, the average grain size is about 3.9 μm and the in-line transmittance is beyond 55% in the region of 500–1600 nm, reaching a maximum transmittance of 64.2% at the wavelength of 1450 nm. The Verdet constant at 633 nm is measured to be −178.9 rad T−1 m−1, which is 33% larger than that of the commercial TGG single crystal (−134 rad T−1 m−1).

Fabrication of Tb3Al5O12 transparent ceramics using co-precipitated nanopowders: The influence of ammonium hydrogen carbonate to metal ions molar ratio

Abstract Terbium aluminum garnet (Tb 3 Al 5 O 12 , TAG) nanopowders were synthesized by the co-precipitation method using ammonium hydrogen carbonate (NH 4 HCO 3 , AHC) as the precipitant. The influence of ammonium hydrogen carbonate to metal ions molar ratio (AHC/M 3+ , R value) on the properties of TAG precursors and powders was investigated by FTIR, XRD and FESEM. It is found that the compositions of the precursors are nearly the same, and all the 1100°C-calcined powders exhibit a pure TAG phase. However, the R value has a significant influence on the morphology and agglomeration degree of TAG precursors and final powders. The precursor with R=3.6 shows a strong agglomeration, which is retained in the resultant powder. For the TAG precursors and powders with R=4.0, 4.4 and 4.8, they show better dispersity and homogeneity. Using the obtained powders as starting materials, TAG transparent ceramics were successfully fabricated by pre-sintering at 1700 °C for 20 h and then HIP post-treating at 1700 °C for 3 h. The ceramic sample with R=4.0 shows the best transparency, and its in-line transmittance exceeds 55% in the region of 500–1600 nm, reaching about 64% at 1450 nm. The microstructures and the magneto-optical properties of the TAG ceramics with different R values were also studied.