High-entropy (YxEr1-x)2(Ti0.2Zr0.2Hf0.2Ge0.2Sn0.2)2O7 oxide: A promising thermal barrier coating material with potential fluorescent Nondestructive Function

Abstract

In this study, high-entropy (Y_xEr_1-x)₂(Ti_0.2Zr_0.2Hf_0.2Ge_0.2Sn_0.2)₂O₇ (where x = 0.01–0.05, 0.1) oxide (YEHEO) with a single-phase fluorite structure has been synthesized via a simple solid-state reaction method and investigated as a promising thermal barrier coating (TBC) material with potential applications in optical pressure sensing. The samples exhibit excellent thermal stability at 1500 °C for 5 h, with a Vickers hardness of 9–10 GPa, comparable to that of traditional yttria-stabilized zirconia (YSZ). Due to the high-entropy effect, the thermal expansion coefficient of these samples is higher than that of YSZ and single-component zirconates, ranging from 12.4879 to 13.0633 × 10⁻⁶ K⁻¹. Under 405 nm laser excitation, the YEHEO samples emit bright green light, which is attributed to the ⁴S_3/2 → ⁴I_15/2 transition of doped Er³⁺. Among all samples, the YEHEO sample with x = 0.03 demonstrates the highest fluorescence intensity, low thermal conductivity (1.38–1.56 W·m⁻¹·K⁻¹), and moderate fracture toughness (2.6 MPa·m^1/2). The luminescence peak center (⁴S_3/2 → ⁴I_15/2) of this sample exhibits a linear redshift with increasing pressure, with a pressure coefficient of 0.0826 nm/GPa. This research provides valuable guidance for the development of novel high-entropy oxide TBC materials with high performance and potential optical stress sensing applications.