A new B-site doped mid-entropy ceramic Gd2(Ti1/3Zr1/3Sn1/3)2O7 for high-temperature thermal barrier coatings applications: preparation process, thermophysical properties, and mechanical properties

Abstract

Thermal barrier coatings (TBCs) are essential for improving the efficiency and service life of advanced aero-engines by providing thermal insulation under extreme operating conditions. As modern aero-engines continue to demand higher inlet temperatures, there is an urgent need to develop new TBC ceramics with superior thermophysical and mechanical properties to extend service life and operational limits. In this work, a mid-entropy pyrochlore ceramic, Gd₂(Ti_1/3Zr_1/3Sn_1/3)₂O₇ (GTZS), was designed by multi-component B-site doping to simultaneously achieve ultra-low thermal conductivity, excellent sintering resistance and enhanced mechanical reliability. Comprehensive characterization including XRD, high-resolution TEM and long-term annealing up to 100 h at 1600 ℃ confirmed that GTZS maintains a stable single-phase pyrochlore structure with an exceptionally low grain growth rate (8.8 nm/h), indicating superior sintering resistance. Additionally, GTZS possessed an ultra-low thermal conductivity (0.92-0.85 W⋅m^-1⋅K^-1, 25-1100 ℃) due to intense phonon scattering induced by structural disorder and excess oxygen vacancies, while the coefficient of thermal expansion (10.5 × 10⁻⁶ K⁻¹, 1200 ℃) is well-matched to that of Al₂O₃ thermally grown oxide (TGO) layers. Mechanical tests revealed a high fracture toughness (2.63 MPa·m^1/2) and a relatively low Young’s modulus (192 GPa), which contribute to improved strain tolerance and resistance to crack propagation. These combined thermophysical and mechanical properties demonstrate the promise of mid-entropy pyrochlore GTZS for next-generation TBC applications.