Effects of thickness and particle size of In2O3 electrode on performance of NH3 sensor
Nano sensing material In2O3 is prepared using self-propagation high-temperature synthesis(SHS)method for fabricating sensing electrodes of mixed potential type NH3 sensors adopting yttria-stabilized zirconia(YSZ)as solid electrolyte and Pt as reference electrode.Morphology of the sensing electrode samples are characterized using XRD,SEM and TEM.It is found through research that as the electrode thickness increasing,more NH3 molecules are absorbed onto the surface of the electrode to participate in electrochemical processes,so that the sensing performance is increased.However,the sensing performance is suppressed if the sensing electrode layer is too thick,because most NH3 molecules are consumed by the gas-solid heterogeneous catalytic reactions before they can penetrate the electrode layer and reach the three-phase boundary(TPB)region.The SEM characterization results show that the optimum thickness of the sensing electrode layer is 104.20 μm.At the same time,effect of particle size on performance is researched.It is found that at calcination temperature of 900 ℃,the sensor shows the highest sensitivity(-64.20mV/decade).The TEM characterization results show that the average particle size of the crystal particles at 900℃ is 75.92 nm.The polarization curve test verifies that the sensor response mechanism conforms to the mixed potential theory.
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