Qiang Liu,Jinbang Li,Jiawei Dai,Zewang Hu,Cong Chen,Xiaopu Chen,Yagang Feng,Jiang Li
Ytterbium doped lutetium oxide (Yb:Lu 2 O 3 ) transparent ceramics were fabricated by vacuum sintering combined with hot isostatic pressing (HIP) of the powders synthesized by the co-precipitation method. The effects of calcination temperature on the composition and morphology of the powders were investigated. Fine and well dispersed 5 at% Yb:Lu 2 O 3 powders with the mean particle size of 67 nm were obtained when calcined at 1100 °C for 4 h. Using the synthesized powders as starting material, we fabricated 5 at% Yb:Lu 2 O 3 ceramics by pre-sintering at different temperatures combined with HIP post-treatment. The influence of pre-sintering temperature on the densities, microstructures and optical quality of the 5 at% Yb:Lu 2 O 3 ceramics was studied. The ceramic sample pre-sintered at 1500 °C for 2 h with HIP post-treating at 1700 °C for 8 h has the highest in-line transmittance of 78.2% at 1100 nm and the average grain size of 2.6 µm. In addition, the absorption and emission cross sections of the 5 at% Yb:Lu 2 O 3 ceramics were also calculated.
In this article, 5 at.% Yb:Lu 2 O 3 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/M 3+ , R value) on the properties of Yb:Lu 2 O 3 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 Lu 2 O 3 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%.
The Yb:Lu 2 O 3 precursor made up of spherical particles was synthesized through the co-precipitation method in the water/ethanol solvent. The 5 at% Yb:Lu 2 O 3 powder is in the cubic phase after calcination at 1100 °C for 4 h. The powder also consists of spherical nanoparticles with the average particle and grain sizes of 96 and 49 nm, respectively. The average grain size of the pre-sintered ceramic sample is 526 nm and that of the sample by hot isostatic pressing grows to 612 nm. The 1.0 mm-thick sample has an in-line transmittance of 81.6% (theoretical value of 82.2%) at 1100 nm. The largest absorption cross-section at 976 nm is 0.96×10 −20 cm 2 with the emission cross-section at 1033 nm of 0.92×10 −20 cm 2 and the gain cross sections are calculated with the smallest population inversion parameter β of 0.059. The highest slope efficiency of 68.7% with the optical efficiency of 65.1% is obtained at 1033.3 nm in quasi-continuous wave (QCW) pumping. In the case of continuous wave (CW) pumping, the highest slope efficiency is 61.0% with the optical efficiency of 54.1%. The obtained laser performance indicates that Yb:Lu 2 O 3 ceramics have excellent resistance to thermal load stresses, which shows great potential in high-power solid-state laser applications.
Highly transparent ceramics of Zr 4+ and Sc 3+ ions co-doped 5 at.%Yb: Lu 2 O 3 were prepared by using wet-chemical precipitant method combined with pressureless sintering in flowing H 2 atmosphere, where Zr 4+ was induced as the sintering aid and Sc 3+ as the band regulators to realizing spectral broadening of Yb:Lu 2 O 3 . The microstructure, broad emission band, PL spectrum and optical properties of the Zr 4+ and Sc 3+ co-doped 5 at.%Yb:Lu 2 O 3 ceramic samples were investigated by SEM, XRD, PL spectrum and other characterization methods. The results indicate that the maxim FWHM of the excitation emission spectrum of Yb:(Lu X Sc 1-X ) 2 O 3 ceramic is 15 nm when x = 0.5. Furthermore, the incorporation of Zr 4+ at a doping concentration of 2 at.% alleviated the microstructural inhomogeneity of the Yb:(Lu 0.5 Sc 0.5 ) 2 O 3 ceramics and significantly reduced the grain size, resulting in high transparency of up to 81.2 % at 1200 nm wavelength. These findings demonstrate a great potential of this ceramic for applications in ultrafast short pulse laser media.
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