Preparation And Performance Of NO₂ Sensors Based On Perovskite Sensing Electrode

Many scholars have paid more attention to the exploration and modification of the sensing electrodes to improve the sensitivity of NO₂ sensors.The perovskite-type oxides have benn considered to be a pretty and sensitive electrode material with the certain advantages in catalytic performance,the stable crystal structure and the lower price.La_0.75Sr_0.25CrO_3-??LSC?was synthesized by the in-situ-wet impregnation technique.The impedance type NO₂ sensor was created by using the YSZ as the solid electrolyte and the LSC as sensing electrode.The sensitive performance was tested at 600 to 700?.The results showed that the LSC are uniformly distributed in the porous framework of YSZ.The best test temperature was 650°C and the optimal impregnation was 60?L.Under this condition,the sensitivity of the sensor at 0.1 Hz was greater than that at 10 Hz,but the stability is less than that at 10 Hz.The sensitivity of NO₂ sensor with non-stoichiometric LSC((La_0.75Sr_0.25)_x CrO_3-?,x=0.95,1.05)sensing electrode was studied.The results show that the non-stoichiometry improves the gas sensing performance of LSC because non-stoichiometric LSC had a stronger adsorption performance to NO₂ and a lower interfacial reaction resistance.By investigating the variation of the transient response curves of sensors with different parameters?Z',Z",|Z|,and??as response signals,it is found that|Z|or?signal change would depends mainly on Z"?interface capacitance?at higher frequencies.The effect of sensing electrode with LSC modified by Ag on sensor sensitivity was studied.The results showed that the interfacial reaction resistance of the sensor was reduced and the stability of the sensor is greatly improved after the LSC was modified by Ag.The response value and sensitivity of the sensor based on(La_0.75Sr_0.25)_0.9Ag_0.1CrO_3-??LSC-0.10Ag?were the best.The LSC-0.10Ag/YSZ/Pt sensor had an operating temperature of 400 to 550°C,and the sensor did not respond to the NO₂ at 600°C.The sensor had a good anti-interference ability to CO₂,CH₄,and NH₃ gases and a good stability.Figure40;Table5;Reference93...