Synergistic effects of high-entropy engineering and particulate toughening on the properties of rare-earth aluminate-based ceramic composites

Rare-earth aluminates (REAlO;) are potential thermal barrier coating (TBC) materials, but the

relatively high thermal conductivity (k,, ~13.6 Wm'K') and low fracture toughness (Kic, ~1.9

MPa·m') limit their application. This work proposed a strategy to improve their properties

through the synergistic effects ofhigh-entropy engineering and particulate toughening.

High-entropy (LaoNd,,Smo,Euo2Gd2)A10; (HEAO)-based particulate composites with different

contents ofhigh-entropy (Lao,Ndo,Smo.Euo,Gd,2),Zr0,(HEZ0) were designed and

successfully prepared by solid-state sintering. The high-entropy feature of both the matrix and

secondary phases causes the strong phonon scattering and the incorporation of the HEZO

secondary phase, remarkedly inhibiting the grain growth of the HEAO phase. As a result.

HEAO-XHEZ0 (x=0,5%,10%,25%, and 50% in volume) ceramic composites show low thermal

conductivity and high firacture toughness. Compared to the most commonly applied TBC material

yttria stabilized-zirconia (YSZ), the HEAO-25%HEZO particulate composite has a lower

thermal conductivity of0.96 ~1.17Wm'K'(298 ~ 1273 K), enhanced fracture toughness of

3.94 + 0.35 MPa-m'”, and comparable linear coefficient of thermal expansion (CTE) of 10.5 x

10-6 K 1. It is believed that the proposed strategy should be revelatory for the design of new

coating materials including TBCs and environmental barrier coatings (EBCs)