Thermal and mechanical properties of metal oxide-doped Gd2Zr2O7 ceramics
摘要
The ongoing pursuit of higher efficiency in gas turbines necessitates thermal barrier coatings (TBCs) that can perform reliably beyond the conventional 1200 °C operational limit of yttria-stabilized zirconia. This study focuses on enhancing the properties of gadolinium zirconate (GZ) ceramics, a prominent candidate for next-generation TBCs, through the strategic incorporation of iron (Fe) and titanium (Ti) as single and co-dopants. The aim was to optimize the ceramic’s thermophysical characteristics and mechanical resilience for aggressive high-temperature environments. All ceramic samples were prepared via a solid-state reaction route involving planetary ball milling and subsequent consolidation by sintering at 1500 °C. The sintered materials were subjected to comprehensive analysis, including X-ray diffraction (XRD) and Field emission scanning electron microscopy (FESEM) for structural and microstructural details, alongside systematic measurements of thermal conductivity, thermal expansion coefficient, hardness, elastic modulus, and fracture toughness. The results demonstrate that all synthesized doped compositions stabilize in the highly ordered pyrochlore structure, marking a clear phase transition from the defect fluorite structure found in the undoped GZ baseline. Point defects introduced by the dopants significantly suppress phonon-mediated heat transfer, culminating in a minimum thermal conductivity of 0.92 W m−1 K−1 recorded at 900 °C for the iron-doped GZ (GFZ) specimen. While the elastic modulus showed general improvement across the doped series, the GFZ composition distinctly exhibited the highest fracture toughness (1.64 MPa m1/2) and a favorable reduction in the brittleness index. These findings confirm that Fe-doped GZ successfully achieves a superior balance between low thermal conductivity and enhanced damage tolerance, positioning it as a highly promising material for advanced TBC systems.