| Summary: | Using the co-precipitation method to synthesize (CeO<sub>2</sub>)<sub>0.95</sub>(Y<sub>2</sub>O<sub>3</sub>)<sub>0.05</sub> (YDC) and solid reaction method to synthesize (CeO<sub>2</sub>)<sub>0.75</sub>(ZrO<sub>2</sub>)<sub>0.25</sub> (ZDC), and the crystal structure, micro-structure, total conductivity and electronic conductivity of the two materials was measured with X-ray diffraction (XRD), scanning electron microscope (SEM), DC van der Pauw and Hebb-Wagner methods. A limiting current oxygen sensor was prepared with YDC solid electrolyte and a ZDC dense diffusion barrier layer by employing platinum pasting bonding. Sensing characteristics of the sensor were obtained at different conditions, including temperature (<i>T</i>), oxygen concentration (<i>x</i>(O<sub>2</sub>)) and water vapor pressure (<i>p</i>(H<sub>2</sub>O)), and the influence of various conditions on sensing performance was studied. The long-term stability of the sensor was measured in an oxygen concentration of 1.2% and at a temperature of 800 °C for 120 h. XRD results show that the phase structure of both YDC and ZDC belongs to the cubic phase. SEM results show that both YDC and ZDC layers are dense layers, which are then qualified to be the composition materials of the sensor. The limiting current (<i>I</i><sub>L</sub>) of the sensor is obtained and the sensor exhibits good sensing characteristics to satisfy the Knudsen model. Log(<i>I</i><sub>L</sub>·<i>T</i>) depends linearly on 1000/<i>T</i> with a squared correlation coefficient (<i>R</i><sup>2</sup>) of 0.9904; <i>I</i><sub>L</sub> depends linearly on <i>x</i>(O<sub>2</sub>) with an <i>R</i><sup>2</sup> of 0.9726; and sensing characteristics are not affected by <i>p</i>(H<sub>2</sub>O). It was found that the oxygen sensor has good long-term stability.
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