In this work, we have prepared a novel yttria-stabilized zirconia fiber (YSZ f )-reinforced (La 1/5 Nd 1/5 Sm 1/5 Gd 1/5 Yb 1/5 ) 2 Zr 2 O 7 porous ceramics (YSZ f /(5RE 1/5 ) 2 Zr 2 O 7 PCs) through a foam-gelcasting-freeze drying process. The microstructure, phase composition, density, porosity, thermal conductivity, and compressive strength of the as-prepared YSZ f /(5RE 1/5 ) 2 Zr 2 O 7 PCs were systematically investigated. In addition, the high-temperature thermal cycle stability and thermally insulating property of the samples were also tested. The results indicated that the as-synthesized YSZ f /(5RE 1/5 ) 2 Zr 2 O 7 PCs (with 25 wt% YSZ fibers) exhibited high porosity, high compressive strength, low thermal conductivity as well as low thermal cycling shrinkage. This work demonstrated that the added YSZ fiber can remarkably improve the strength of (5RE 1/5 ) 2 Zr 2 O 7 PCs with the high porosity, and as-developed YSZ f /(5RE 1/5 ) 2 Zr 2 O 7 PCs would be an excellent candidate for high-temperature thermal insulator materials.
The high-entropy rare earth zirconate (La 1/5 Nd 1/5 Sm 1/5 Gd 1/5 Yb 1/5 ) 2 Zr 2 O 7 porous ceramics ((5RE 1/5 ) 2 Zr 2 O 7 PCs) were prepared using a foam-gel casting-freeze drying method combined with segmented calcination process. The results of SEM, TEM , and XRD analyses of the (5RE 1/5 ) 2 Zr 2 O 7 PCs indicated the formation of a defective fluorite crystal structure, with the rare earth elements homogeneously distributed. Meanwhile, the as-prepared (5RE 1/5 ) 2 Zr 2 O 7 PCs exhibited high porosity, low bulk density, low thermal conductivity , and relatively high compressive strength . Moreover, the high-temperature thermal conductivity of the samples was evaluated, and the results showed that the (5RE 1/5 ) 2 Zr 2 O 7 PCs maintain a thermal conductivity of 0.150 ± 0.002 W m −1 K −1 even at 1000 °C. The strategy used in this paper can be extended to the synthesis of other high-entropy porous ceramics with high porosity and low thermal conductivity, which is suitable for applications as thermal insulation materials.
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