Alkaline-Earth Metals-Doped Pyrochlore Gd(2)Zr(2)O(7) as Oxygen Conductors for Improved NO(2) 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.