**Abstract**

The evaluation of plasma resistance and the characteristics of yttria ceramics fabricated by calcination yttria as a starting material without dopants under an oxidation atmosphere were investigated. Regardless of the starting materials, as-received and calcined yttria powder, XRD patterns showed that all samples have Y2O3 phase. The three cycling processes inhibited a large grain, which occurs frequently during the yttria sintering, and a high-density ceramic with a homogeneous grain size was obtained. The smaller the grain size, the larger were the Young's modulus and KIC. Compared to Al2O3 and ZrO2 ceramics, yttria ceramics showed 3 times larger plasma resistance and 1.4–2.2 times lower weight loss during the plasma etching test, respectively. The characteristics of pure hot-pressed yttria ceramics tempered in an oxidation atmosphere are also investigated. Even though the color variation of the hot-pressed Y2O3 ceramics was due to the sintering temperatures, the oxidation process turned the color of the Y2O3 ceramics into white. In addition, oxygen defects also affected the weight change and microstructure of the Y2O3 ceramics. The Y2O3 ceramic sintered at 1600°C had obtained a full density. As the sintering temperature increased, small homogeneous grains grew to large grains which affected the Vickers hardness.

**Keywords:** as-received yttria, calcined yttria, three-repeated cycle sintering, homogeneous grain, plasma resistance, hot-pressed yttria ceramics, oxidation, homogeneous grain, full density
