Effect of sintering temperature on microstructural and optical properties of transparent yttria ceramics fabricated by spark plasma sintering

Yttria nanopowder was used to fabricate transparent yttria ceramics by spark plasma sintering at temperatures ranging from 1200 °C to 1600 °C for 20 min. The microstructure of fracture cross section and optical transmittance of the products were characterized by Field Emission-Scanning Electron Microscope (FE-SEM) and Fourier-transform infrared spectrophotometer (FTIR). With increasing the sintering temperature, densification occurs up to 1500 °C, whereas the mean grain size of yttria ceramics was first increased and then decreased markedly. The highest density and the lowest mean grain size of yttria ceramic reached to 99.58% and 0.53 μm at 1500 °C, respectively. The best in-line transmittance was at 1500 °C, with transmittance being about 80% in the range of 3-5 μm, which was close to the theoretical value of yttria.