| Summary: | High strength transparent Y<sub>2</sub>O<sub>3</sub> 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 Y<sub>2</sub>O<sub>3</sub> ceramics. Grain growth was limited accordingly with increasing the heating rate. The ball milling process of the commercial Y<sub>2</sub>O<sub>3</sub> powders is likely to further enhance the sinterability during the SPS processing. The dense Y<sub>2</sub>O<sub>3</sub> 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 <i>H<sub>v</sub></i> 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 <i>K<sub>IC</sub></i>, 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 Y<sub>2</sub>O<sub>3</sub> ceramics with the excellent optical and mechanical properties.
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