Transparent Er2O3 ceramics fabricated by high-pressure spark plasma sintering

Fabrication of transparent Er₂O₃ ceramics was carried out by high-pressure spark plasma sintering (HP-SPS). The color and in-line transmittance of these ceramics was highly sensitive to the sintering parameters. Samples exhibited a strong pink or wine color after sintering at 1150 °C under 600 MPa or 1250 °C under 250 MPa, respectively. This was confirmed to be a result of oxygen vacancies created during the sintering process and high sensitivity of Er₂O₃ to the strong reducing atmosphere in the SPS apparatus. Post-sintering annealing in an air furnace led to elimination of oxygen vacancies and increased transparency. Additionally, the photoluminescence intensity and phosphorescence lifetime of annealed (pink) samples was higher and shorter, respectively, compared to that of the reduced (wine-colored) samples.