A new application of CexZr1-xO2 as dense diffusion barrier in limiting current oxygen sensor

CexZr1-xO2 (x = 0.25, 0.5 and 0.75) was synthesized by solid phase chemical reaction synthesis and characterized by X-ray diffraction (XRD), thermal expansion, Hebb-Wagner method and DC van der Pauw method. ZrO2 has a high melting point and CeO2 has a variable valence state, which can make the CexZr1-xO2 material have mixed ionic-electronic conductivity and stability. The synthesis method has the advantages of having a lower synthesis temperature and no waste liquid discharge, which is beneficial to energy conservation and environmental protection. A limiting current oxygen sensor was prepared with Ce0.75Zr0.25O2 dense diffusion barrier and ZrO2 stabilized by 9 mol% Y2O3 (9YSZ) solid electrolyte by Pt sintered-paste method. Limiting current plateau of the oxygen sensor was obtained and the effects of operate temperature (T), oxygen concentration (x(O-2)) and water vapor pressure (p(H2O)) on the limiting current was studied, respectively. The results show that the Ce0.75Zr0.25O2 material has maximum electronic and total conductivity at 800 degrees C and is the most suitable ceramic material to be a dense diffusion barrier of limiting current oxygen sensor. The oxygen sensor exhibits good sensing characteristics under different research conditions, including different T, x(O-2) and p(H2O). The limiting current is related to various research factors, for example, log(I-L.T) depends linearly on 1000/T, I-L depends linearly on x(O-2) and I-L is not influenced obviously by p(H2O). The experiment supplements the application of mixed conductor material CexZr1-xO2 (x = 0.25, 0.5 and 0.75) as a dense diffusion barrier in limiting current oxygen sensor.