Enhanced studies on the mechanism of gas selectivity and electronic interactions of SnO₂/Na⁺-ionic conductors

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• 关键词：Tin oxide ; Gas sensor ; NASICON ; Ionic conductor ; Solid electrolyte ; Composites ; Electronic impedance ; EIS ; Catalytic conversion ; FTIR ; Sol– ; gel ; Thick film ; Selectivity ; VOC
• 刊名：Sensors and Actuators B ; Chemical
• 出版年：2007
• 期刊代码：161_09254005
• 类别：et
• 出版时间：10 January 2007
• 卷：120
• 期：2
• 页码：378-385
• 文件大小：805 K

摘要

The selectivity of metal oxide gas sensors (MOG) can be improved significantly by forming composites with solid ionic conductor additives. First investigations were done using model composites of SnO₂/Natrium Super Ionic Conductor (NASICON) with the result of a huge sensitivity enhancement to substances ending with R–OH, R–HO or R–COOH groups and a reduction of sensitivity to other gas components. This selectivity of the new composite to those functional groups could be confirmed by catalytic conversion measurements with FTIR-spectroscopy at three gas components, respectively. The specific conductivity of the NASICON containing composites is significantly lower than that of pure SnO₂. Advanced studies show that the activation energy of the bulk-conductivity increases by approximately 30%in the presence of NASICON. In spite of high volume parts of NASICON (20%), no polarization effects were found (a complete Ohmic current–voltage behavior) and mainly the resistive part of the electrical impedance is influenced.