The Properties And Fabrication Of Resistance/Potential-type Gas Sensors Based On LaFeO₃/ZnO

With the development of science and technology, our life has become much convenient. But at the same time, it has also caused great environment pollutions. Especially in recent years, because of the mass emission of industrial waste gas and automobile exhausts, the atmospheric is polluted unavoidably. Otherwise, with the internet of things put forward and smart home appeared, people are care for the inner air pollution more than before. So, the researchers pay a great attention to fabricate high performance and low power consumption gas sensor. In this paper, the ZnO nanoparticles and LaFeO₃ particles have been prepared as the resistor type gas sensor to research their gas sensing properties. Later, the YSZ nanofibers are prepared as solid electrolyte material, and the ZnO nanoparticles and LaFeO₃ particles prepared before are taken as the sensitive electrode and reference electrode respectively. Then the ZnO|YSZ|LaFeO₃ mixed potential gas sensor is fabricated and the gas sensing properties of which were also studied. The main results are summarized as follows.1. ZnO nanoparticles are synthesized by chemical vapor deposition ?CVD? method and characterized by X-ray diffraction ?XRD?, field-emission scanning electron microscopy ?FE-SEM? and transmission electron microscopy ?TEM?. The specific surface and the pore size of ZnO nanoparticles are measured by specific surface and pore size analysis instrument. The ethanol sensing properties of the gas sensor based on ZnO nanoparticles are investigated by exposing them to different concentrations of gaseous ethanol at various temperatures. At an operating temperature of 150?, the gas sensor has good performance. The response value to 100 ppm gaseous ethanol at optimum operating temperature is 21.6, and corresponding response and recovery times are about 4 and 32 s, respectively. The results indicate that ZnO nanoparticles synthesized by CVD have potential applications for fabricating high performance and low power consumption ethanol sensors.2. LaFeO₃ ?LFO? particles were synthesized by citrate sol-gel method, and characterized by XRD, FE-SEM, TEM, X-ray photoelectron spectroscopy ?XPS? and specific surface & pore size analysis instrument. To investigate the formaldehyde ?HCHO? sensing properties, the side-heating gas sensor based on LFO particles was fabricated. The LFO particles-based gas sensor presented high response and good selectivity to HCHO at an operating temperature of 100?. At the range of 1-50 ppm HCHO, the LFO particles-based gas sensor exhibits a nearly linear response, and the linear correlation coefficient is 0.99. The response time and recovery time are about 33 and 27 s, respectively. The results indicate that LFO particles synthesized by citrate sol-gel method have potential applications for fabricating high performance and low power consumption HCHO gas sensor.3. Yttria-stabilized zirconia ?YSZ? nanofiber were synthesized by electro spinning technique, and characterized by XRD and FE-SEM. The ZnO|YSZ| LaFeO₃ side heating mixed potential gas sensors was fabricated by using the manufacturing technology of gas sensor. The gas sensing properties was investigated by using semiconductor device testing system under different operating voltages and ethanol concentrations. At different operating voltages, the gas sensor presented good linear responses. Specially, when operating voltage was 8 V, the response time and recovery time of the gas sensor to 500 ppm ethanol were 15 s and 10 s respectively, and the sensor shows good repeatability and stability. The results indicate that the ZnO|YSZ|LaFeO₃ mixed potential gas sensors has good gas sensing properties.Through the above three parts of the work, we systematically studied the gas-sensing properties of based on ZnO/LaFeO₃ resistive and mixed potential type gas sensors, such as sensitivity, selectivity. Our work can provide experimental and theoretical guidance for subsequent researchers studying metal oxide gas sensor deeply. Meanwhile, this study may offer a powerful reference for the manufacturing high performance low power consumption gas sensor.