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Yttrium (Y 2 O 3) nanopowders were synthesized via the precipitation method using ammonium hydrogen carbonate (AHC) as the precipitant. The influences of calcination temperature on the composition and morphology of the powders were investigated. Fine Y 2 O 3 powders with low-agglomeration were obtained by calcining the precursor at 1100 °C for 4 h. The primary crystallites were calculated to be ∼47 nm in size and weakly agglomerated to particles with size of ∼79 nm. Using the synthesized powders as the starting materials, Y 2 O 3 ceramics were fabricated by vacuum sintering at different temperatures combined with HIP post-treatment. The densification and micro-structure evolution of the Y 2 O 3 ceramics were systematically investigated. The ceramic sample vacuum sintered at 1500 °C for 2 h and post-HIPed at 1550 °C for 3 h exhibited a uniform and fine microstructure with the average grain of about 1.0 μm. The in-line transmittance of the ceramic sample reached 80.1% at 1100 nm. • Y 2 O 3 transparent ceramics were prepared by two-step sintering from the precipitated nano-powders. • Y 2 O 3 ceramics with the average grain size of 1.0 μm and in-line transmittance of 80.1% at 1100 nm were obtained. • The prepared Y 2 O 3 transparent ceramics are attractive for host materials without any sintering additives. [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]

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]

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]

The 1 at.% Er:CaF 2 transparent ceramics were prepared by the air pre-sintering and hot isostatic pressing (HIP) using nano-powders synthesized by the co-precipitation method. The influence of pre-sintering temperature and HIP post-treatment on the density, microstructures, optical and photoluminescence properties of Er:CaF 2 ceramics were investigated. After HIP post-treatment (650 °C × 2 h, 100 MPa Ar), the pores in the pre-sintering ceramics were gradually eliminated and high transparency was achieved. The maximum in-line transmittance of the HIPed 1 at.% Er:CaF 2 reaches 90.5% at 1600 nm (2.8 mm thickness) when the pre-sintered temperature is 625 °C.The absorption cross section was calculated. The strong absorption peak at 1530 nm reveals an unfavorable infrared emission. The main emission peak at 1530 nm, which is derived from the 4I 13/2 → 4I 15/2 transition of Er3+, can be observed under excitation of 980 nm. Owing to the long lifetime of 4I 13/2 (32.3 ms) and large emission cross section, the 1 at.% Er:CaF 2 transparent ceramics have great potential to achieve a good NIR laser performance in the 1.5 μm region. • Er:CaF 2 transparent ceramics were prepared by air pre-sintering and HIP post-treatment. • Fine-grain Er:CaF 2 transparent ceramics with uniform distribution were obtained. • Er:CaF 2 transparent ceramics showed high in-line transmittance of 90.5% at 1600 nm. [ABSTRACT FROM AUTHOR]