Effect of the heating rate on the spark-plasma-sintering (Sps) of transparent y₂ o₃ ceramics: Microstructural evolution, mechanical and optical properties

High strength transparent Y₂ O₃ ceramics were fabricated from commercial powders using spark plasma sintering (SPS) technique by optimizing the heating rate. The heating rate significantly influenced the microstructures and the optical/mechanical properties of the Y₂ O₃ ceramics. Grain growth was limited accordingly with increasing the heating rate. The ball milling process of the commercial Y₂ O₃ powders is likely to further enhance the sinterability during the SPS processing. The dense Y₂ O₃ ceramics, which were sintered by SPS with 100^◦ C/min, showed good transmittance range from visible to near infrared (IR). For a high heating rate of 100^◦ C/min, the in-line transmittance at a visible wavelength of 700 nm was 66%, whereas for a slow heating rate of 10^◦ C/min, it reduced to 46%. The hardness H_v tends to increase with increasing the heating rate and rigorously followed the Hall–Petch relationship; that is, it is enhanced with a reduction of the grain size. The toughness K_IC, on the other hand, is less sensitive to both the heating rate and the grain size, and takes a similar value. This research highlighted that the high heating rate SPS processing can fabricate fully dense fine-grained Y₂ O₃ ceramics with the excellent optical and mechanical properties.