Functional Design of Semiconductor Gas Sensors for Development of Odor Sensors

本课题的研究重点是对有机气体传感器进行功能性设计，以研制具有高灵敏度和高选择性的有机气体传感器，并采用半导体金属氧化物负载贵金属和不负载贵金属的方法，研究了内电极型有机气体传感器的灵敏度随厚度的变化规律。发现在所测试的传感器中，只有In_2O_3-MgO（5mol%）负载3.0wt%Pt（3.0Pt/In_2O_3-MgO（5mol%））在300 ℃时对DMA的灵敏度高于TMA。在3.0Pt/In_2O_3-MgO（5mol%）传感器表面镀上一层TiO_2或0.5Pt/TiO_2层，可进一步提高DMA灵敏度。单层传感器的DMA灵敏度高是由于它具有较高的生成氮氧化物活性和较高的生成氮氧化物活性。TMA氧化时产生的亚胺与传感器材料上的化学吸附氧反应性较强，而NO_X是TMA的氧化产物，起干扰气体的作用，用In_2O_3-MgO（5mol%）敏感层、0.5Ir/TiO_2涂层和两层之间的电极组成双层膜传感器，可实现高的NH_3灵敏度。研究发现，选择NH_3氧化程度适中而不产生大量NO_X的传感器材料和NH_3还原NO_X为N_2的高活性涂层是研制高灵敏度NH_3传感器的首要条件。

The present project was focused on functional design of semiconductorgas sensors for development of odor sensors capable of detecting of odor components, such as trimethylamine (TMA), dimethylamine (DMA) and ammonia, with high sensitivity and selectivity.Thickness dependence of TMA gas sensistvity of sensors equipped with interior electrodes have been investigated by employing semiconductor metal oxides loades with and without different amounts of noble metals. It has revealed that optimum design of both the thickness and the catalytic activity for TMA oxidation of sensor materials is of primary importance for the development of TMA gas sensors.It was found that In_2O_3-MgO (5mol%) loaded with 3.0 wt% Pt (3.0Pt/In_2O_3-MgO (5mol%)) was the only sensor which exhibited higher sensitivity to DMA than TMA at 300ﾟC,among the sensors tested. The DMA sensitivity was further enhanced by coating the surface of 3.0Pt/In_2O_3-MgO (5mol%) sensor with a TiO_2 or 0.5Pt/TiO_2 layr. The high DMA sensitivity of the single layr sensor was found to be attributed to its high activity for producing ethylenimine and less activity for producing NO_X. Ethylenimine produced during the oxidation of TMA is more reactive with chemisorbed oxygen on the sensor material, while NO_X are oxidation products of TMA and act as interference gases.High NH_3 sensitivity could be realized with the doible layr sensor consisting of an In_2O_3-MgO (5mol%) sensing layr, a 0.5Ir/TiO_2 coating layr atop the sensing layr and electrodes between these two layrs. It was found that selection of both the sensor materials having moderate NH_3 oxidation without producing large amounts of NO_X and the coating layr exhibiting high activity for reduction of NO_X into N_2 by NH_3 is of primary importance for developing an NH_3 sensor having high sensitivity.