Impact of ZrO2 alloying on thermo-mechanical properties of Gd3NbO7

Abstract

The ZrO2 alloying effect is widely used to optimize the thermo-mechanical properties of potential thermal barrier coatings. In this study, dense x mol% ZrO2-Gd3NbO7 with C2221 space group were manufactured via a solid-state reaction. The crystalline structure was determined through X-ray diffraction and Raman spectroscopy, when the surface morphology was observed by scanning electron microscopy. ZrO2-Gd3NbO7 had identical orthorhombic crystal structures, and there was no second phase. The crystalline structure of ZrO2-Gd3NbO7 shrunk with the increasing ZrO2 content as indicated by XRD and Raman results. The heat capacity and thermal diffusivity of ZrO2-Gd3NbO7 were 0.31–0.43 J g−1 K−1 (25–900 °C) and 0.25–0.70 mm2/s (25–900 °C), respectively. It was found that ZrO2-Gd3NbO7 had much lower thermal conductivity (1.21–1.82 W m−1 K−1, 25–900 °C) than YSZ (2.50–3.00 W m−1 K−1) and La2Zr2O7 (1.50–2.00 W m−1 K−1). The thermal expansion coefficients (TECs) were higher than 10.60 × 10−6 K−1 (1200 °C), which were better than that of YSZ (10.00 × 10−6 K−1) and La2Zr2O7 (9.00 × 10−6 K−1). The mechanical properties of Gd3NbO7 change little with the increasing ZrO2 content, Vickers hardness was about 10 GPa, and Young's modulus was about 190 GPa, which was lower than YSZ (240 GPa). Compared with previous work about alloying effects, much lower thermal conductivity was obtained. Due to the high melting point, high hardness, low Young's modulus, ultralow thermal conductivity and high TECs, it is believed that ZrO2-Gd3NbO7 is promising TBCs candidate.