YTaO<sub>4</sub>/Y₂Zr₂O₇ Dual-Phase Ceramics with Enhanced Vickers Hardness, Fracture Toughness and High Thermal Expansion Properties for Thermal Barrier Coating Applications
Rare-earth tantalates (RETaO<sub>4</sub>) are considered as a type of emerging thermal barrier coating materials applied to the hot components of gas turbines and aerospace engines due to their excellent thermal stability, high-temperature fracture toughness, corrosion resistance and ext...
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| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-03-01
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| Series: | Metals |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2075-4701/15/3/307 |
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| Summary: | Rare-earth tantalates (RETaO<sub>4</sub>) are considered as a type of emerging thermal barrier coating materials applied to the hot components of gas turbines and aerospace engines due to their excellent thermal stability, high-temperature fracture toughness, corrosion resistance and extremely low thermal conductivity. However, the relatively low hardness and thermal expansion coefficients may limit their service lifetime in a harsh engine environment. To address the current limitation of rare-earth tantalates and further optimize the mechanical and thermal properties, the defective fluorite-structured Y₂Zr₂O₇ (YZ) was introduced as a second phase into the YTaO<sub>4</sub> (YT) matrix to form YT<sub>1−x</sub>–YZ<sub>x</sub> (x = 0, 0.25, 0.5, 0.75, 1) composite ceramics in this work. The mechanical and thermal properties of YT<sub>1−x</sub>–YZ<sub>x</sub> composite ceramics are significantly improved compared to pure-phase YTaO<sub>4</sub> ceramics. The Vickers hardness of YT<sub>1−x</sub>–YZ<sub>x</sub> (x = 0.25, 0.5, 0.75) composite ceramics is 9.1~11.3 GPa, which are 2~2.5 times higher than that of YTaO<sub>4</sub> (4.5 GPa). Among them, YT<sub>0.75</sub>–YZ<sub>0.25</sub> exhibits a maximum fracture toughness (3.7 ± 0.5 MPa·m<sup>1/2</sup>), achieving a 23% improvement compared to YTaO<sub>4</sub> (3.0 ± 0.23 MPa·m<sup>1/2</sup>) and a 118% improvement compared to Y<sub>2</sub>Zr<sub>2</sub>O<sub>7</sub> (1.73 ± 0.28 MPa·m<sup>1/2</sup>). The enhancement is attributed to the combined effect of the intrinsic strengthening of the second phase, as well as the residual stress and grain refinement caused by the introduction of a second phase. Additionally, the thermal expansion coefficients of YT<sub>1−x</sub>–YZ<sub>x</sub> composite ceramics at 1673 K range from 10.3 × 10⁻⁶ K⁻<sup>1</sup> to 11.0 × 10⁻⁶ K⁻<sup>1</sup>, which is also higher than that of YTaO<sub>4</sub> (10.0 × 10<sup>−6</sup> K<sup>−1</sup>). Consequently, the superior mechanical and thermal properties indicate that YT–YZ composite ceramics possess promising application prospects for thermal barrier coatings. |
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| ISSN: | 2075-4701 |