Low temperature-sintering and microstructure of highly transparent yttria ceramics

Highly transparent yttria ceramics were successfully fabricated by vacuum pre-sintering and post hot isostatic pressing (HIP) treatment both under very low temperatures synthesized from powders by a co-precipitated method. The morphologies and microstructures, density and thermal mechanical changes, and optical properties of ceramics under different processing stages were systematically characterized by (F)SEM, TMA, optical microscope and UV-Vis-IR spectrophotometer, respectively. The full densification of yttria ceramics could be achieved just at as low as 1450 °C for 4 h (vacuum pre-sintering) and 1400 °C for 3 h (post-HIP). The fabricated ceramics exhibited a uniform and fine microstructure and high optical performance. The average grain size was as small as 0.74 μm. The in-line transmittance reached 81.7% at 1100 nm (1 mm thickness). The transparent yttria ceramics were attractive without any sintering additives at such low pre-sintering and post-HIP temperatures.