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

Abstract

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(O2)) 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 ºC 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(O2) and p(H2O). The limiting current is related to various research factors, for example, log(IL·T) depends linearly on 1000/T, IL depends linearly on x(O2) and IL 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.