Lu4Hf3O12 ceramics as potential top-coat materials for thermal/environmental barrier coatings

Abstract

The mismatch of thermal expansion coefficient (CTE) between thermal barrier coatings (TBCs) and environmental barrier coatings (EBCs) is the key factor that affects the durability of T/EBCs in aero-engine environments. To alleviate the CTE mismatch, the novel TBC materials with relatively low CTE are needed. In this study, Lu4Hf3O12 with δ-phase rhombohedral structure was synthesized by solid-state reaction using Lu2O3 and HfO2 as the raw materials. Lu4Hf3O12 ceramics exhibited outstanding phase stability up to 1600 °C and comparable mechanical properties to 8 wt% Y2O3 stabilized ZrO2 (8YSZ) as well as great resistance against water-vapour/oxygen corrosion. Additionally, it possessed the thermal conductivity of 1.20 W/m·K at 1000 °C, about 43% lower compared to traditional 8YSZ material (2.1–2.22 W/m·K), and coefficient of thermal expansion (CTE) of 8.46 × 10−6 K−1 (10.38 × 10−6 K−1 for 8YSZ). These results preliminarily reveal that Lu4Hf3O12 could be considered as a potential material for thermal insulation top-coat in the field of T/EBCs.