Preparation of yttria nanopowders for use in transparent ceramics by dry ball-milling technique

To evaluate the effectiveness of dry ball-milling, yttria powders were ball-milled, and the optimal sample was spark plasma sintered to fabricated transparent yttria ceramics. The characterization of the powders and pellets were analyzed using XRD, FESEM, UV/VIS/NIR and FTIR spectrometer throughout the whole experimental process. The results indicated that ball-milling can significantly decrease yttria particle size and enhance the specifice surface area. The best duration is 20 h ball-milling with average particle size and specifice surface area of 64 nm and 20.4 m2/g, respectively. Transparent yttria ceramic was made up of grains in the size range of approximately 0.67 μm and the relative density was 99.8%. The in-line transmittance of the SPS-sintered yttria ceramic (2.5 mm thick) reached 83% in the infrared region, which is very close to the theoretical value of yttria.