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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. [ABSTRACT FROM AUTHOR]

Transparent 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). [ABSTRACT FROM AUTHOR]

In this article, 5 at.% Yb:Lu2O3 transparent ceramics were fabricated by vacuum sintering combined with hot isostatic pressing (HIP) posttreatment using co‐precipitated nano‐powders. The influence of precipitant molar ratio, ammonium hydrogen carbonate, to metal ions (AHC/M3+, R value) on the properties of Yb:Lu2O3 precursors and calcined powders was investigated systematically. It was found that the powders with different R value calcined at 1100°C for 4 hours were pure cubic Lu2O3 but the morphologies of precursors and powders behaved differently. The opaque samples pre‐sintered at 1500°C for 2 hours grew into transparent ceramics after HIP posttreatment at 1750°C for 1 hour. The final ceramic with R = 4.8 showed the best optical quality with the in‐line transmittance of 79.7% at 1100 nm. The quasi‐CW laser operation was performed at 1034 nm and 1080 nm with a maximum output power up to 8.15 W as well as a corresponding slope efficiency of 58.4%. [ABSTRACT FROM AUTHOR]

The 0.05 at.% Co:MgAl2O4 precursor was synthesized by the coprecipitation method from a mixed solution of magnesium, aluminum, and cobalt nitrates using ammonium carbonate as the precipitant. 0.05 at.% Co:MgAl2O4 transparent ceramics were successfully obtained via vacuum sintering and hot isostatic pressing (HIP) of 0.05 at.% Co:MgAl2O4 nanopowder calcined at 1100°C for 4 hours. The properties of powder and ceramics were comprehensively investigated. X‐ray diffraction (XRD) results showed that Co:MgAl2O4 nanopowder had a pure spinel phase. Also, the in‐line transmittances of the HIP posttreated Co:MgAl2O4 ceramics with the thickness of 1.2 mm were 82% at 400 nm and 84.7% at 900 nm. The average grain sizes of 0.05 at.% Co:MgAl2O4 ceramics before and after the HIP posttreatment were 11 and 28 μm, respectively. The calculated ground state absorption cross section of 0.05 at.% Co:MgAl2O4 ceramics was 2.9 × 10−19 cm2, indicating that this ceramics is a promising material applied as a saturable absorber for passive laser Q‐switches in the 1.3‐1.7 μm domain. [ABSTRACT FROM AUTHOR]

In this study, transparent ZnS ceramics were hot pressed from precipitated wurtzite nanopowders. Influences of sintering temperature on wurtzite-to-sphalerite phase transition and densification behavior have been investigated. Maximum sphalerite phase content and highest densification were simultaneously obtained in the sample hot pressed at 900°C with uniaxial pressure of 250 MPa for 2 h, which accounts for the highest transmittance above 55% and 70% in the range 2-5 μm and 5-13 μm, respectively. Preferred orientation of wurtzite grains in [002] direction paralleled to the press direction was also observed, which is supposed to be benefit to transmittance by reducing birefraction and second-phase scattering. Furthermore, second-phase scattering caused by wurtzite grains has been investigated. It is found that fine grains are conducive to hot-pressed ZnS ceramics with high transmittance, especially in the short-wavelength range. [ABSTRACT FROM AUTHOR]

• Tb 2 Ti 2 O 7 transparent ceramics were fabricated from co-precipitated nano-powders by two-step sintering. • The in-line transmittance of Tb 2 Ti 2 O 7 ceramics reaches 65.5 % at 1064 nm. • The Verdet constant of Tb 2 Ti 2 O 7 ceramics (−229.0 ± 0.6 rad·T−1 m−1@633 nm) is 71 % higher than TGG crystals. • Tb 2 Ti 2 O 7 ceramics are very promising magneto-optical materials for Faraday isolators. Transparent Tb 2 Ti 2 O 7 magneto-optical ceramics were fabricated from co-precipitated nano-powders by vacuum pre-sintering with hot isostatic pressing (HIP) post-treatment. The formation of pyrochlore phase, decomposition of the precursor, and the morphology of powders calcined at different temperatures were investigated. The in-line transmittance of Tb 2 Ti 2 O 7 ceramics, which were pre-sintered at 1350 ℃ for 2 h with HIP post-treatment at 1450 ℃ for 3 h and subsequently annealed at 800 ℃ for 20 h in NH 3 atmosphere, reaches 65.5 % at 1064 nm. The Verdet constant of Tb 2 Ti 2 O 7 ceramics is −229.0 ± 0.6 rad·T−1 m−1 at the wavelength of 633 nm, which is 71 % higher than that of the commercial Tb 3 Ga 5 O 12 crystals. Tb 2 Ti 2 O 7 magneto-optical ceramics show a promising application for Faraday rotators. [ABSTRACT FROM AUTHOR]

(Tb 0.99 Ce 0.01) 3 Ga 5 O 12 powders were synthesized by calcining the co-precipitated precursor at 1150°C. The powders showed low-agglomeration and high sinterability, so that the powders compact could be sintered to be transparent by a two-step sintering method. By using the best synthesis condition of air pre-sintered at 1525°C for 3 h and hot isostatic pressed at 1500°C for 3 h under 150 MPa, (Tb 0.99 Ce 0.01) 3 Ga 5 O 12 transparent ceramics with the in-line transmittance of 81.7% at 1064 nm were successfully prepared. The Verdet constant of the (Tb 0.99 Ce 0.01) 3 Ga 5 O 12 ceramics at 633 nm was about −143.4 ± 3.2 rad T−1 m−1, which was about 7% higher than that of the Tb 3 Ga 5 O 12 crystals (−134 rad T−1 m−1). Image, graphical abstract [ABSTRACT FROM AUTHOR]

Using the 1 at.% Er:SrF 2 nano-powders synthesized by the co-precipitation method as starting powders, 1 at.% Er:SrF 2 transparent ceramics were successfully prepared by air pre-sintering at different temperatures for 2 h combined with hot isostatic pressing (HIP) post-treatment at 600 °C for 2 h under 100 MPa Ar. The influences of the pre-sintering temperature on optical quality, microstructure, phase composition and EPR spectrum of ceramics were investigated. Among all the HIP post-treated 1 at.% Er:SrF 2 ceramics in the thickness of 2.5 mm, the sample pre-sintered at 650 °C shows the best optical quality, whose transmittance at 2500 nm and 1500 nm reaches 83.4% and 73.6%, respectively. Furthermore, the spectral characteristics of this ceramic sample were systematically analyzed. The fluorescence lifetime for the 1 at.% Er:SrF 2 ceramics at 1530 nm is 49.62 ms. The strongest absorption and emission cross section for the peaks at around 1530 nm are 6.20 × 10−21 and 3.47 × 10−21 cm2, respectively. In brief, the above findings indicate that the Er:SrF 2 ceramics is a promising candidate as middle infra-red laser gain media. • Pure-phase Er:SrF 2 nano-powders were synthesized by the co-precipitation method. • 1 at.% Er:SrF 2 ceramics with fine grains were fabricate by two-step sintering. • Spectral properties for 1. at.% Er:SrF 2 ceramics were systemically explored. [ABSTRACT FROM AUTHOR]

Transparent ytterbium doped calcium-fluoride (Yb:CaF 2) ceramics were successfully fabricated by air pre-sintering and hot isostatic pressing (HIP) post-treatment from the powders synthesized by the co-precipitation method. The influence of pre-sintering temperature on the densification, microstructures and optical quality of 5 at.% Yb:CaF 2 ceramics was systematically investigated. The ceramic sample pre-sintered at 650 °C for 2 h and HIP post-treated at 650 °C for 1 h shows the best transparency with the in-line transmittance of 90% at 1200 nm. The upper level lifetime of the Yb3+ in Yb:CaF 2 ceramics was evaluated to be 1.95 ms by the pinhole method. In addition, the laser emission from an optimized 5 at.% Yb:CaF 2 ceramic sample yields in the maximum output power of 0.81 W with a maximum slope efficiency of 22.6% at 1028.5 nm under quasi-CW pumping. • Yb:CaF 2 nano-powders were synthesized by the co-precipitation method. • Yb:CaF 2 ceramics with the in-line transmittance of 90% were obtained by air pre-sintering and HIP post-treatment. • Yb:CaF 2 ceramic laser with the slope efficiency of 22.6% and the output power of 0.81 W was obtained at 1028.5 nm. [ABSTRACT FROM AUTHOR]

Red cerium doped 8 mol% yttria stabilized zirconia (Ce-doped 8YSZ) transparent ceramics were prepared by the two-step sintering method using commercial powders as raw materials. The ceramics after pre-sintering at 1300 °C for 2 h and hot isostatic pressing (HIP) post-treatment at 1700 °C for 3 h showed a high in-line transmittance and a large redness due to the 4f-5d transition absorption of Ce3+ at about 390–550 nm , and the values were 70.7% (@ 700 nm) and 57.1, respectively. The influences of air annealing temperature on the color and optical quality of the red Ce-doped 8YSZ transparent ceramics were studied. With the increase of annealing temperature, the color of the ceramics shifted from red to orange-red and then to nearly colorless, while the redness value decreased from 57.1 to 0.8 due to the oxidation of Ce3+ to Ce4+. The in-line transmittance of the ceramics decreased from 70.7% to 46.5% at 700 nm due to the expansion of the compressed residual pores, and the cut-off wavelength blue-shifted from 580 to 380 nm due to the disappearance of absorption peak at about 390–550 nm of Ce3+after annealing at 1200 °C. • Transparent Ce-doped yttria stabilized zirconia ceramics with bright red color were prepared by two-step sintering. • The ceramics showed a high in-line transmittance of 70.7% (@ 700 nm) and a large redness of 57.1. • With the increase of annealing temperature, ceramics color changed from red to orange-red and then to nearly colorless. [ABSTRACT FROM AUTHOR]

ZnGa 2 O 4 (ZGO) persistent luminescence (PersL) ceramics doped with different concentrations of Cr3+ were prepared by the co-precipitation method and hot isostatic pressing (HIP) post-treatment. After HIP post-treatment, the ZGO PersL ceramics was significantly improved from opaque to transparent visual appearance due to the elimination of micro-pores during HIP process. The effects of Cr3+ concentration on the morphology, transmittance and PersL properties of ZGO PersL ceramics were systematically investigated. The ZGO PersL ceramics with higher Cr3+ dopant concentrations show less micro-pores and higher transmittance, which indicates that the Cr3+ can also work as a sintering additive to increase the density and to improve the optical quality of ZGO PersL ceramics. The photoluminescence excitation (PLE) and emission (PL) intensities increase with the increase of Cr3+ concentration up to 0.25 at.%. At yet higher Cr3+ concentrations, the ZGO PersL ceramics exhibits weaker PL and PLE intensities which is probably caused by the concentration quenching effect. However, the PersL decay curves show that the PersL performance of ZGO ceramics increases with increasing Cr3+ concentrations, indicating that the doping by Cr3+ ions may cause another traps formation leading to stronger and longer PersL. The PersL decay curves of all ZGO PersL ceramics were fitted by the second-order exponential function, indicating that at least two kinds of traps with different electron release rates exist in the ZGO ceramics. The influence of Cr3+ concentration on the thermoluminescence (TL) of ZGO PersL ceramics was also studied, and the results showed that the TL curves of the pre-sintered ceramics shifted to lower temperatures, indicating that the depth of trap related to Cr3+ ions is shallower than the depth of trap caused by the intrinsic defects. • Cr3+:ZnGa 2 O 4 ceramics were prepared by co-precipitation and HIP post-treatment. • Cr3+ can work as a sintering aid to improve the optical quality of ZGO ceramics. • Concentration quenching occurs when Cr3+ concentration is more than 0.25 at-%. • Oxygen vacancy can lead to the formation of deeper trap. [ABSTRACT FROM AUTHOR]

Ytterbium-doped yttrium oxide (5 at.%Yb:Y 2 O 3) nanopowders were synthesized by the co-precipitation method in this work. The influence of the molar ratio of ammonium hydrogen carbonate to metal ions (NH 4 HCO 3 /M3+, defined as R) on the properties of the precursors and powders was studied. The powders calcined at 1100 °C from the precursors with different R showed the same phase as the pure cubic Y 2 O 3. However, the agglomerations of the calcined powders were influenced by the R evidently and the 5 at.%Yb:Y 2 O 3 powders with R = 4.0 showed better dispersivity. Using the obtained powders as starting materials, 5 at.%Yb:Y 2 O 3 transparent ceramics were fabricated by vacuum sintering and hot isostatic pressing (HIP) post-treating. The 5 at.%Yb:Y 2 O 3 ceramics with R = 4.0 possessed the best optical quality with the in-line transmittance of 81.2% at 1100 nm with fine grains. In addition, the microstructures of the 5 at.%Yb:Y 2 O 3 transparent ceramics with different R values were also studied and the HIP post-treated ceramics exhibited homogeneous microstructures. Meanwhile, the absorption and emission cross-sections of the 5 at.%Yb:Y 2 O 3 ceramics were calculated to be 0.99 × 10−20 cm2 at 976 nm and 0.97 × 10−20 cm2 at 1031 nm, respectively. The gain spectra also were obtained from the absorption and emission spectra. • Yb:Y 2 O 3 nano-powders with the average particle size of 59 nm were obtained by the co-precipitation method. • Fine-grained 5 at%Yb:Y 2 O 3 transparent ceramics were prepared by vacuum sintering and hot isostatic pressing. • In-line transmittance of 5 at%Yb:Y 2 O 3 ceramics from the optimal nano-powders reaches 81.2% at 1100 nm. [ABSTRACT FROM AUTHOR]

Transparent Tb 2.45 Hf 2 O 7.68 ceramics were fabricated successfully by reactive sintering at 1700 °C for 3 h with hot isostatic pressing (HIP) post-treatment at 1700 °C for 3 h. In-line transmittance of the Tb 2.45 Hf 2 O 7.68 ceramic specimen with the thickness of 2.0 mm reached 79.4% at 1064 nm. X-ray diffraction was used to verify the existence of pyrochlore phase and the occupation sites of Tb3+ were discussed. Elemental mapping showed no secondary phase in Tb 2.45 Hf 2 O 7.68 ceramics. Verdet constant of the Tb 2.45 Hf 2 O 7.68 ceramics at 633 nm is -165.6 rad•T−1•m−1, which is 23.6% higher than that of commercial Tb 3 Ga 5 O 12 crystal (-134 rad•T−1•m−1) and 8.4% higher than that of Tb 2 Hf 2 O 7 (-152.8 rad•T−1•m−1). Tb 2.45 Hf 2 O 7.68 ceramics with high Verdet constant are promising to be used in compact Faraday rotators. [Display omitted] [ABSTRACT FROM AUTHOR]

Yb,La:CaF 2 nano-powders doped with different Yb3+ concentrations as 1, 2, 3, 5 at.% were synthesized by the co-precipitation method. The Yb,La:CaF 2 powders which were in pure cubic CaF 2 phase. The Yb,La:CaF 2 transparent ceramics were prepared by the air pre-sintering at different temperatures for 2 h with hot isostatic pressing (HIP) post-treatment at 650 °C for 2 h under 62 MPa Ar. The influences of the Yb3+ doping concentration and pre-sintering temperature on optical quality and microstructures of ceramics were investigated. Among all the fabricated ceramics, the 3 at.%La,5 at.%Yb:CaF 2 transparent ceramics pre-sintered at 650 °C showed the best optical quality. For the 1 mm thickness sample, its in-line transmittance reached 92.6% at 1200 nm. Furthermore, the absorption and the emission cross sections of the ceramics were calculated. The strongest absorption and emission peaks are around 977 nm. The lifetime for the Yb,La:CaF 2 transparent ceramics at 1028 nm increased first and then decreased with further increasing the Yb3+ doping concentrations. • Yb,La:CaF 2 transparent ceramics were prepared by the air pre-sintering and HIP post-treatment. • The role of the pre-sintering temperature and Yb concentration on the Yb,La:CaF 2 ceramics were studied. • In-line transmittance of the fabricated 5 at.%Yb,3 at.%La:CaF2 ceramics is 92.6% at 1200 nm. [ABSTRACT FROM AUTHOR]

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. • TAG transparent ceramics were prepared by solid-state reactive sintering and HIP post-treatment. • Influences of TEOS amount on microstructure and optical quality of TAG ceramics were investigated. • Prolonging the pre-sintering time can improve the in-line transmittance of TAG transparent ceramics. [ABSTRACT FROM AUTHOR]