Study on La2(Zr0.2Y0.2Yb0.2Nb0.2Ti0.2)2O7@YSZ core-shell structural composite oxide for thermal barrier coating

High-entropy oxides are promising thermal barrier coating (TBC) materials owing to their low thermal conductivity. However, they have poor fracture toughness. To overcome this limitation, this study designed a core–shell structural composite oxide. By combining low-toughness La 2 (Zr 0.2 Y 0.2 Yb 0.2 Nb 0.2 Ti 0.2 ) 2 O 7 (L(ZYYNT)O) high-entropy oxide and high-toughness yttria-stabilized zirconia (YSZ), a new La 2 (Zr 0.2 Y 0.2 Yb 0.2 Nb 0.2 Ti 0.2 ) 2 O 7 @YSZ composite was designed and chemically synthesized. Subsequently, the properties of the composite oxide were evaluated. Results show that the thermal conductivity and coefficient of thermal expansion of the L(ZYYNT)O@YSZ composite-structure ceramic are approximately 1.103 W·m − 1 ·K − 1 at room temperature, after correcting for porosity, and approximately 9.5356 × 10 − 6 K − 1 at 1000 °C, respectively. Moreover, its fracture toughness is approximately 3.45 MPa·m 1/2 , which is 43% higher than that of the L(ZYYNT)O high-entropy oxide. However, the interface formed between L(ZYYNT)O and YSZ was incoherent. The interfacial binding energy between the L(ZYYNT)O high-entropy oxide and the YSZ was determined using a Materials Studio simulation and is approximately 3.315 J/m 2 . Thus, the study demonstrates that the L(ZYYNT)O@YSZ composite-structure oxide exhibits potential as a TBC material.