The effect of Fe doping on the electrical conductivities of CaZrO3 and its sensing performance in limiting current oxygen sensor

CaZr1-xFexO3 (x = 0, 0.1, 0.2 and 0.3) solid solutions were synthesized by solid state reaction method. Crystalline structure, microstructure, density, thermal analysis, electronic conductivity and total conductivity were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Archimedes method, thermogravimetric analysis (TG), Hebb-Wagner and DC van der Pauw method, respectively, and the effect of Fe content on the above properties was investigated. Sensing characteristics of a limiting current oxygen sensor with CaZr0.7Fe0.3O3 dense diffusion barrier and YSZ solid electrolyte including recovery time, long-term stability and the influence of water vapor pressure on the limiting current were measured and discussed. CaZr1-xFexO3 series belong to an orthorhombic perovskite structure. The Fe doped CaZrO3 samples have fine density and grains size decreases with increasing Fe content x. Electronic conductivity increases with increasing x and the CaZr0.7Fe0.3O3 sample has the highest electronic conductivity. Total conductivity increases to a maximum for the CaZr0.8Fe0.2O3 sample and then decreases as the increase of x. The recovery time of the sensor is about 100 s and water vapor pressure does not affect the limiting current.