Effects of Nb ⁵⁺ doping on thermal properties of Gd ₂ (Zr _{1− x} Nb _x ) ₂ O _{7+ x} ceramics

Pyrochlore Gd2(Zr1−xNbx)2O7+x (x = 0, 0.05, 0.1, 0.15) ceramic materials were synthesised using a high-temperature solid-state reaction method. The phase structure, thermal expansion coefficient and thermal conductivity of Gd2(Zr1−xNbx)2O7+x were investigated in this work. The results show that with the introduction of Nb2O5, Gd2(Zr1−xNbx)2O7+x ceramic materials present a cubic pyrochlore structure. Meanwhile, Gd2(Zr1−xNbx)2O7+x ceramics have clear grain boundaries. The thermal expansion coefficient of Gd2(Zr1−xNbx)2O7+x ceramic materials reduces from 11.4576 × 10−6 to 10.7919 × 10−6 K−1 (larger than 10 × 10−6 K−1), while its thermal conductivity gradually increases with the doping of Nb5+ ions. Considering their comprehensive properties, Gd2(Zr1−xNbx)2O7+x compounds may be considered as promising thermal barrier coatings materials.