Effect of Nb Dopant on the Oxidation Behavior of Zr2[Al(Si)]4C5 at 1000–1300°C

Nb-doped Zr2[Al(Si)]4C5 solid solutions were prepared by in situ hot pressing method and their high-temperature oxidation behavior at 1000°–1300°C were investigated. The oxidation resistance of [Zr0.9(Nb0.1)]2[Al(Si)]4C5 solid solutions is improved remarkably compared with Zr2[Al(Si)]4C5 without dopant. The improved oxidation resistance is due to the formation of a more protective oxide scale consisting of (Zr,Nb)O2, Nb2Zr6O17, Al2O3, and mullite, in which (Zr,Nb)O2 solid solution is more effective than ZrO2 in depressing the inward diffusion of oxygen. In addition, the decrease of cracks in the oxide scale above 1100°C in Nb-doped sample is also beneficial to the improved oxidation resistance.