In the present work transparent Y2O3 ceramics were made by slip casting and vacuum sintering of nanopowders with sodium poly-acrylic acid（PAA-Na） as dispersant.The rheological properties of Y2O3 nanopowder slurry were investigated using different amounts of dis-persant and solid contents.The microstructures and transmittance of the sintered ceramics were also studied by means of scanning electron microscopy（SEM） and ultra-violet visible spectrometry.The results showed that rheological behaviors of the Y2O3 nanopowder slurry were effectively promoted by sodium polyacrylic acid.Highly dispersive and stable slurries were obtained as the dispersant was added over 1.0 dwb% under the fixed conditions of pH 11 and 45 wt.% solid content.All the slip cast green bodies were sintered into highly dense ceramics after sintering at 1700 oC for 5 h in vacuum,wherein the sample added with 1.1% sodium polyacrylic acid exhibited the highest relative den-sity of 99.36% and transmission of 30% at 800 nm wavelength.
HUO DiZHENG YanchunSUN XudongLI xiaodongLIU Shaohong
We report the laser output of transparent Nd：YAG （Nd：Y3Al5O12） ceramics fabricated from Nd：YAG precursors through the microwave-assisted homogenous precipitation （MAHP） method. Pure phase and uniform Nd：YAG nano-powders with average sizes less than 100 nm were obtained by heating treatment of.the Nd：YAG precursor particles aged for 6 d in vessel with humidity of 30%-50% at 25℃. Transparent Nd：YAG ceramic pellets were obtained by vacuum sintering at 1730℃ for 10 h. Laser output （305 roW） with a slope efficiency of 5.1% was realized through an end-pumped configuration. Our results indicate that the MAHP method could potentially be used for the fabrication of laser ceramic products,
ZHANG Xiaolin LIU Duo WANGJiyang YU Haohai QIN Haiming SANG Yuanhua LIU Hong
Red-emission （Y0.95Eu0.05）2O3 submicron spheres and microplates were selectively obtained via hydrothermal precursor synthesis （150 °C, 12 h） followed by calcination at 1000 °C. Characterizations of the products were carried out by combined means of XRD, FT-IR, FE-SEM and PL analysis. The precursors could be modulated from basic-carbonate submicron spheres to normal carbonate microplates by increasing the molar ratio of urea to Y＋Eu from 10 to 40-100. The resultant oxides largely retain their respective precursor morphologies at 1000 °C, but morphology confined crystal growth was observed for the microplates, yielding more enhanced exposure of the （400） facets. Both the （Y0.95Eu0.05）2O3 spheres and microplates exhibit nearly identical positions of the PL bands and similar asymmetry factors of luminescence [I（5D0→7F2）/I（5D0→7F1）, ～11] under 250 nm excitation, but the microplates show a significantly strong red emission at ～613 nm （ ～1.33 times that of the spheres） owing to their larger particle size and denser packing of primary phosphor crystallites.
We reported on the successful synthesis of the Nd：YAG （Nd：Y3Al5O12） nano-powders by using urea as the precipitant with the microwave assisted homogeneous precipitation （MAHP） method. The different microstructural characteristics of the Nd：YAG nano-powders were affected by the concentrations of （Y3＋＋Nd3＋） and Al3＋ （[Y3＋＋Nd3＋]=0.06 mol/L, [Al3＋]=0.1 mol/L）, aging time （6 d） and aging condition （in vessel）. The optimum microstructural characteristics of the high quality Nd：YAG nano-powders leading to transparent Nd：YAG ceramics including the pure YAG phase, the smallest crystallite size, a uniform crystallite size distribution, less density defects, uniform micro-components and the proper molar ratio of （Y3＋＋Nd3＋） and Al3＋ （0.6148） were discussed.
