Pyrochlore Pr2Zr1.95In0.05O7+δ oxygen conductors: Defect-induced electron transport and enhanced NO2 sensing performances

Abstract

Abstract The work proposed a distinct arrangement to construct the amperometric-type NO2 sensor using pyrochlore-phase Pr2Zr2O7 as oxygen-defect conductor. An effective co-doping strategy at A and B sites was explored to prepare the defective Pr2-xMxZr1.95In0.05O7+δ (PMZI, M\u202f=\u202fCa, Sr, Ba) oxygen conductors. DFT results show that the band structure of solid electrolyte are dependent of the doping elements at A and B sites. A-site doping theoretically causes 48f and 8b oxygen defects, yet only 48f oxygen defect for B-site doping. Oxygen defect energy shows that Ca2+ doping at A site can be inclined to 8b oxygen defects, as opposed to Sr2+ and Ba2+ incorporation that can cause migratable 48f oxygen defects. DFT simulation indicates that the thermally excited electrons for the Ca2+ doping are uneasier to enter the conduction band through two deeper impurity levels, compared to Sr2+ and Ba2+ doping, as the dark current is lower for the PCZI sensors. The oxygen-defect induces both the electron transport and enhanced NO2 sensing performances. The result of amperometric response obviously exhibits that the ΔI value of the optimized PCZI (0.02) sensor with high sensitivity (224\u202fnA/ppm) is 15.11 and 12.26 times as high as the pure Pr2Zr2O7 and commercial YSZ sensors, respectively, exhibiting the potential industrial application prospect.