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

This work proposed a novel strategy to fabricate highly-stable NO₂ sensor based on a pyrochlore-phase Gd₂Zr₂O₇ oxygen conductor. The incorporation of alkaline-earth metals distinctly enhances the sensing performance of the Gd₂Zr₂O₇ based sensors. The excellent sensor based on Gd_1.95Ca_0.05Zr₂O_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 NO₂ at 500 °C, which is better than that of commercial YSZ under the same condition. The ΔI value towards NO₂ is much higher than those towards other gases (CH₄, C₃H₆, C₃H₈, CO, NO, SO₂, C₂H₄, CO₂ and C₂H₆), exhibiting excellent selectivity for detecting NO₂. 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-xM_xZr₂O_7+δ are expected to a promising application in automotive vehicles.