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

Abstract

Pyrochlore Gd₂(Zr_1−xNb _x )₂O_7+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(Zr_1−xNb _x )₂O_7+x were investigated in this work. The results show that with the introduction of Nb₂O₅, Gd₂(Zr_1−xNb _x )₂O_7+x ceramic materials present a cubic pyrochlore structure. Meanwhile, Gd₂(Zr_1−xNb _x )₂O_7+x ceramics have clear grain boundaries. The thermal expansion coefficient of Gd₂(Zr_1−xNb _x )₂O_7+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(Zr_1−xNb _x )₂O_7+x compounds may be considered as promising thermal barrier coatings materials.