A new approach to the obtaining of Y₂O₃ optical ceramics with submicron grain size

DOI: 10.62564/M4-DC1234

Dariia Chernomorets^1,2, Vojtěch Nečina³, Andreana Pinacastelli², Pietro Galizia², Jan Hostaša<sup>2

1</sup>Institute for Single Crystals of NAS of Ukraine, Ukraine
²CNR-ISSMC, 64 Via Granarolo, 48018 Faenza (RA), Italy
³Department of Glass and Ceramics, University of Chemistry and Technology, Czech Republic


Y₂O₃ ceramics can be used as IR-transparent material due to its excellent properties. The transparency of ceramics is ensured by the absence of defects, and the necessary mechanical properties can be achieved by limiting the grain size [1]. Traditional approaches to the obtaining of such materials, i.e. hot pressing and vacuum sintering, lead to the grains' growth up to hundreds of microns [2]. Sintering aids, such as ZrO₂, reduce the grain size by an order of magnitude, which is not enough for some applications [3]. Solving the problem is possible with the simultaneous application of spark plasma sintering, as well as ZrO₂. The conditions for the formation of Y₂O₃ optical ceramics with an average grain size of less than 200 nm have been determined for the first time. Initial Y₂O₃ nanopowders doped with 0-15 mol.% ZrO₂ were obtained by high-energy milling, optical ceramics were synthesized by spark plasma sintering at 1500 °C for 10 min at 80 MPa. It is shown that the addition of ZrO₂ as a sintering aid leads to the formation of a homogeneous, almost non-porous microstructure. A significant decrease in the ceramic grain size is observed from 7.4 μm for pure Y₂O₃ to <200 nm for doped ceramics. According to XRD data, no secondary phases were detected, which is consistent with SEM results and indicates the formation of a solid solution of composition (Y₁₋ₓZrₓ)₂O₃. An increase in the concentration of zirconium oxide leads to a decrease in lattice parameters due to the replacement of Y³⁺ ions by Zr⁴⁺ ions, which have a smaller ionic radius. It was found that the Vickers microhardness increases from 7.1 for undoped yttrium oxide ceramics to 11.2 GPa for Y₂O₃ with 15 mol.% ZrO₂. The conditions for the formation of transparent Y₂O₃ ceramics, characterized by an average grain size of <200 nm and a transmittance of 82% at a wavelength of 5 μm (3 mol.% ZrO₂, T=1500 °С, t=10 min), were determined.

Keywords
Transparent ceramics; spark plasma sintering; yttrium oxide.

Acknowledgments
Not provided

References
[1] D. Chernomorets, et al., Effect of Milling Parameters on the Morphology and Sinterability of the Yttrium Oxide Powders for Transparent Ceramics, Open Ceram., 2023. V.15, 100391. [2] L. Wen, et al., Synthesis of Yttria Nanopowders for Transparent Yttria Ceramics, Opt. Mater., 2006. V.29, P.239-245. [3] X. Hou, et al., Study on the Effect and Mechanism of Zirconia on the Sinterability of Yttria Transparent Ceramic, J. Eur. Ceram. Soc., 2010. V.30, P.3125-3129.