Fabrication of Transparent Yttria Ceramics by Spark Plasma Sintering

Rapid densification of yttria (Y₂O₃) ceramics without sintering aids via spark plasma sintering at relatively low temperature of 1300°C for 40 minutes at two-step pressure profile, followed by post-annealing at 1050°C for 6 hours in air was attempted. Effect of preload pressure on microstructure, Vickers hardness, fracture toughness and optical in-line transmittance was investigated. Densification during spark plasma sintering did not involve any phase transformation and all phases have shown cubic structure according to X-ray analysis. The highest hardness and fracture toughness value was recorded to be 7.60±0.18 GPa and 1.16±0.07 MPa m^{1/2} with 10 MPa preload and 100 MPa final load. In addition to this, the highest transmittance with a value of 76.7% at a wavelength of 2000 nm was obtained when studied with 10 MPa preload and 100 MPa final load.