Thermal performance regulation of high‐entropy rare‐earth disilicate for thermal environmental barrier coating materials

Abstract

We prepared the novel high‐entropy (xRE1/x)2Si2O7 (RE = Y, Yb, Er, Sc, Gd and Eu, x = 2–6) ceramics by a two‐step method for the application of thermal environmental barrier coatings (TEBCs), and the effect of configuration entropy and lattice distortion on microstructures and thermal properties at high temperature were investigated. The results showed that the configuration entropy resulted from mass disorder can only contribute to the stability of thermal properties and microstructure. Lattice distortion should be responsible for reduction in thermal properties, which may be due to the enhancement of atomic nonharmonic vibration, resulting in intensified phonon scattering and hindering atomic amplitude oscillation. As‐prepared high‐entropy (Y1/6Yb1/6Er1/6Sc1/6Gd1/6Eu1/6)2Si2O7 ceramic exhibited the relatively low thermal diffusivity, thermal conductivity and coefficient of thermal expansion, which were 0.89–0.50 mm2 s–1, 1.99–2.50 W m–1 K–1 and (3.01–3.78) × 10–6 K–1 in the temperature range of 293–1373 K, respectively. This work provides a solid guarantee for the application of TEBC materials.

Design rules for the thermal and elastic properties of rare-earth disilicates

“…[Tb] along with CTE data extracted from the literature from dilatometry and high-temperature XRD techniques for RE 2 Si 2 O 7 [54,60,65,66], listed in Tables II and III, and plotted against the average RE cation radius in Figure 3.…”

Significantly improved corrosion resistance of high‐entropy rare‐earth silicate multiphase ceramics against molten CMAS

“…High‐entropy RE silicates, referring to a multiprincipal solid solution consisting of four or more RE components, have attracted wide attention due to its outstanding molten CMAS corrosion resistance and lower thermal conductivity 15,16 . Wang et al 17 .…”

“…13,14 High-entropy RE silicates, referring to a multiprincipal solid solution consisting of four or more RE components, have attracted wide attention due to its outstanding molten CMAS corrosion resistance and lower thermal conductivity. 15,16 Wang et al 17 prepared a high-entropy RE disilicate (5RE 0.2 ) 2 Si 2 O 7 (RE = Yb, Y, Lu, Sc, and Gd) and found that the high-entropy RE disilicate exhibited a good molten CMAS corrosion resistance, and the thickness of the apatite reaction layer was only 25 μm after corrosion at 1400 • C for 20 h. Wang et al 13 also reported the molten CMAS corrosion resistance of a high-entropy (4RE 0.25 ) 2 Si 2 O 7 (RE = Er, Tm, Yb, and Lu) at high temperature. The results showed that the thickness of reaction layer was approximately 300 μm after corrosion at 1500 • C for 50 h. Tian et al 18 only measured the ability of highentropy RE monosilicate ((xRE 1/x ) 2 SiO 5 (RE = Ho, Lu, Yb, and Eu)) to resist molten CMAS corrosion at low temperature, and its thickness of reaction layer was up to 125 μm after corrosion at 1300 • C for 20 h. Therefore, we conclude that although the high-entropy RE silicates showed a significant improvement in the corrosion resistance of molten CMAS compared to single-component RE silicates, the thickness of the reaction layer was still very high during long-term corrosion at high temperature, which will be catastrophic for EBCs with the thickness of only tens to hundreds of microns.…”

Microstructure and property evolution of high‐entropy rare‐earth silicate T/EBCs during thermal aging

“…In recent years, high‐entropy rare‐earth zirconates and silicates had been extensively investigated 23–25 . Ren et al.…”

“…In recent years, high-entropy rare-earth zirconates and silicates had been extensively investigated. [23][24][25] Ren et al found that the (Y 1/4 Ho 1/4 Er 1/4 Yb 1/4 ) 2 SiO 5 bulk material displayed improved properties, such as Young's modulus, thermal conductivity, and thermal expansion, indicating that it might be a T/EBC candidate. 23 Liao et al prepared (Y 1/3 Dy 1/3 Er 1/3 ) 2 SiO 5 , (Y 1/3 Dy 1/3 Lu 1/3 ) 2 SiO 5 , (Y 1/4 Dy 1/4 Ho 1/4 Er 1/4 ) 2 SiO 5 , and (Yb 1/4 Dy 1/4 Ho 1/4 Er 1/4 ) 2 SiO 5 bulk materials, which possessed lower CTE and thermal conductivity than that of the single-component RE 2 SiO 5 .…”