Li Zheng,Zhang Le,Zhou Tianyuan,Wang Lixi,Wong Ching Ping,Yang Hao,Zhang Qitu
A novel spray co-precipitation method was adopted to synthesize well dispersed nanocrystalline Y 2 O 3 powders for transparent ceramics. Several analytic techniques such as XRD, SEM, BET and UV–Vis–NIR spectrophotometer were used to determine the properties of coprecipitated powders, and the microstructure and optical properties of as-fabricated ceramics. The influences of the aging time on powders and ceramics were systematically investigated. Precursors were completely reached to yield the Y 2 O 3 phase after being calcined at 1250 °C in air. The calcined Y 2 O 3 powders exhibited an approximately spherical morphology with narrow size distribution and weak agglomeration, with mean particle size of ~140 nm. The co-precipitated nanopowders with an aging time of 12 h exhibited the best sintering activity due to the low agglomeration, and the in-line transmittance of Y 2 O 3 ceramic sintered at 1800 °C for 8 h in vacuum reached to 77.2% at 1064 nm (1 mm thickness).
A modified vibrating screen method was employed to prepare granulated Y2O3 powders, which were used to fabricate transparent ceramics. The granulation process was carried out with yttrium-stabilized zirconia balls (5 mm in diameter) in a 200-mesh screen, which was vibrated by a Heidolph shaker. After passage through the vibrating screen, the sub-micron Y2O3 particles were converted into large granules and collected in the bottom chamber of the sieve. Compared with the original powders, the granulated powders had a smaller repose angle of 34.09° and larger apparent and tap densities with sharp rises of 50.54 and 32.07%, respectively, indicating a good flowability and filling properties. A high transmittance of 82% at 2500 nm was achieved for ceramics prepared using the granulated powders by vacuum sintering and hot isostatic pressing (HIP).
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