Y2O3(Yttrium oxide) ceramics are known to be an important optical material for mid-infrared (IR) windows and domes, owing to its high transmittance, broad transmittance range, and superior chemical stability. However, the unsatisfactory mechanical and thermal properties of Y2O3 ceramics have severely restricted their application. Therefore, those properties in extreme situations still require further improvement.
A research team led by Professor ZHANG Long from Key Laboratory of Materials for High Power Lasers, Shanghai Institute of Optics and Fine Mechanics of the Chinese Academy of Sciences, has successfully fabricated fine-grained pureY2O3 transparent ceramic with improved mechanical and thermal performance.
In their experiment, the nitrate pyrogenation method was applied to synthesize Y2O3nanopowders; to achieve high thermal conductivity of the final ceramics, no sintering additives were used. The final Y2O3ceramics were fabricated with a hybrid sintering method combining low-temperature presintering and a subsequent hot isostatic pressing (HIP).
The HIP-treated Y2O3ceramic sample presintered at 1350°C provided the optimum microstructure with an average grain size of 0.5 μm, and a high average IR transmittance of 83.0% in the 3–5 μm wavelength region was obtained. Owing to the reduced grain size, the flexure strength and Vickers hardness of the Y2O3 ceramic sample have been improved to 180 MPa and 8.4 GPa, respectively. The thermal conductivity of non-doped fine-grain Y2O3 ceramic is approximately 12.72 W·m-1 K-1 at room temperature, which is significantly higher than that of ZrO2-doped samples (7.02 W·m-1 K-1).
The significantly improved mechanical properties and thermal conductivity of Y2O3ceramic should produce higher thermal shock resistance, which will render the material suitable for high-temperature applications.
The work, entitled "Fabrication of fine-grained undoped Y2O3 transparent ceramic using nitrate pyrogenation synthesized nanopowders ", were published in Ceramics International on Dec. 1st 2018.
SEM image of HIP-treated Y2O3ceramic sample with a presintering temperature at 1350°C
In-line optical transmittance spectra of the HIP-treated ceramic samples with different presintering temperatures
High-temperature thermal conductivity of the achieved Y2O3 ceramic and the ZrO2-doped Y2O3ceramic
Mr. Cao Yong
General Administrative Office
Shanghai Institute of Optics and Fine Mechanics, CAS