Synthesis, Processing, and Properties of Submicrometer‐Grained Highly Transparent Yttria Ceramics

In this article, we report on the fabrication of 0.3‐μm average grain‐sized transparent yttria ceramics using a modified two‐step sintering approach. This process yielded full densification of the yttria ceramics with a drastically reduced grain growth. These transparent yttria ceramics exhibited a transparency equivalent to that of single crystals in the near‐infrared spectral region. The microhardness and fracture toughness of the 0.3‐μm average grain‐sized transparent yttria ceramics fabricated by a modified two‐step sintering were found to exceed those of ∼300‐μm average grain‐sized transparent yttria ceramics fabricated by conventional sintering by 25 and 70%, respectively.