Xuewei Luo,Shuo Huang,Ruiqi Huang,Chunhui Xu,Shuen Hou,Hongyun Jin
Single-phase high-entropy rare-earth zirconate (Dy 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Yb 0.2 ) 2 Zr 2 O 7 with excellent high-temperature phase stability at 1600 °C was designed and synthesized. After being heated at 1600 °C for 1 ∼ 50 h, the average grain size of the sample increases only from 0.74 μm to 2.22 μm, indicating a high anti-sintering ability. The fracture toughness is 2.07 ± 0.03 MPa m 1/2 (25 °C), which is 50% higher than lanthanum zirconate. The local lattice distortions induced by the atomic interactions and atomic-size mismatch are considered to be responsible for the strong anti-sintering ability and improved fracture toughness. In addition, the thermal expansion coefficient and thermal conductivity of (Dy 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Yb 0.2 ) 2 Zr 2 O 7 are 10.59 × 10 -6 K -1 (25 ∼ 1500 °C) and 1.14 ± 0.09 W·m -1 ·K -1 (1500 °C), respectively. The outstanding combination of anti-sintering ability, mechanical behavior , and thermophysical properties of (Dy 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Yb 0.2 ) 2 Zr 2 O 7 highlights its great potential for next-generation thermal barrier coating applications.
The microstructure of plasma-sprayed nanostructured yttria-stabilized zirconia (YSZ) coatings may change during high-temperature exposure, which would influence the coating performance and service lifetime. In this study, the phase structure and the microstructural evolution of 3YSZ (zirconia-3 mol% yttria) and 5YSZ (zirconia-5 mol% yttria) nanostructured coatings were investigated by means of sintering at 1400 °C for 50–100 h. The microhardness, elastic moduli, and thermal shock cycles of the 3YSZ and 5YSZ nanostructured coatings were also investigated. The results showed that the redistribution of yttrium ions at 1400 °C caused the continuous increase of monoclinic-phase zirconia, but no obvious inter-splat cracking formed at the cross-sections, even after 100 h. Large voids appeared around the nanoporous zone because of the sintering of nanoscale granules upon high-temperature exposure. The microhardness and elastic moduli of the nanostructured coatings first increased and then decreased with increasing sintering times. The growth rate of the nanograins in the 3YSZ coating was lower than that in 5YSZ, which slowed the changes in 3YSZ coating porosity during sintering. Although the 3YSZ coating was prone to monoclinic phase transition, the experimental results showed that the thermal shock resistance of the 3YSZ coating was better than that of the 5YSZ coating.
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