Alkaline-Earth Metals-Doped Pyrochlore Gd2Zr2O7 as Oxygen Conductors for Improved NO2 Sensing Performance

This work proposed a novel strategy to fabricate highly-stable NO 2 sensor based on a pyrochlore-phase Gd 2 Zr 2 O 7 oxygen conductor. The incorporation of alkaline-earth metals distinctly enhances the sensing performance of the Gd 2 Zr 2 O 7 based sensors. The excellent sensor based on Gd 1.95 Ca 0.05 Zr 2 O 7+δ exhibits rapid response-recovery characteristics with the maximum response current value (ΔI = 6.4 μA), extremely short 90% responce (3 s) and 90% recovery (35 s) time towards 500 ppm NO 2 at 500 °C, which is better than that of commercial YSZ under the same condition. The ΔI value towards NO 2 is much higher than those towards other gases (CH 4 , C 3 H 6 , C 3 H 8 , CO, NO, SO 2 , C 2 H 4 , CO 2 and C 2 H 6 ), exhibiting excellent selectivity for detecting NO 2 . The response signal basically maintains a stable value of 6.4 μA after the sensors was stored for half a month and a month. The outstanding selectivity and highly stability of the NO 2 sensors based on Gd 2−x M x Zr 2 O 7+ δ are expected to a promising application in automotive vehicles.