Humidity Influence on the CO2Response of Potentiometric Sensors Based on NASICON Pellets with New Compositions, Na3Zr2−(x/4)Si2−xP1+xO12(x= 1.333)
Humidity Influence on the CO2Response of Potentiometric Sensors Based on NASICON Pellets with New Compositions, Na3Zr2−(x/4)Si2−xP1+xO12(x= 1.333)
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DOI：
10.1111/j.1151-2916.2002.tb00136.x
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发表时间：
2004-12
影响因子：
3.9
通讯作者：
H. Aono;Y. Sadaoka;L. Montanaro;E. Bartolomeo;E. Traversa
中科院分区：
文献类型：
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作者：
H. Aono;Y. Sadaoka;L. Montanaro;E. Bartolomeo;E. Traversa
CO2 气体传感器是使用 Na3Zr2−(x/4)Si2−xP1+xO12 系统中新成分的 NASICON 型致密陶瓷制造的。块状陶瓷是由溶胶-凝胶处理的粉末制备的。对于x=0.667和x=1.333的组合物获得致密电解质。相对于具有常规成分的 NASICON，观察到可烧结性得到改善，这归因于液相烧结。使用这些致密样品的二氧化碳气体传感器在干燥大气中表现出稳定的电动势 (emf) 响应，类似于双电子电化学反应的理论能斯特值。对于成分 x= 1.333 的 NASICON 样品也观察到了这一点，其显示出的电导率远低于具有常规成分的 NASICON 的电导率。电动势随着二氧化碳气体浓度的变化而快速变化，并观察到稳态值。 CO2 吸附和解吸的响应时间非常快，特别是在高 CO2 浓度下。研究了湿度对 CO2 传感性能的影响。在潮湿的 CO2 气体中，特别是在低 CO2 浓度下，灵敏度较低，响应较慢。在不同气体流速下进行二氧化碳传感测量，以评估测量电极处发生的反应。观察到测量电极上发生副反应，即形成氧化钠。在干燥气体中，反应在低CO2浓度和小流量下发生，而在潮湿环境中反应强烈增强，并且在整个CO2浓度范围内发生。然而，从潮湿气体切换到干燥气体后，传感器性能恢复。这表明，由于电极处 Na2Ox 的形成，湿度会影响电动势，因此，固体电解质本身不会因湿度而降解。
CO2-gas sensors were fabricated using NASICON-type dense ceramics with new compositions in the Na3Zr2−(x/4)Si2−xP1+xO12system. The bulk ceramics were prepared from sol-gel-processed powders. Dense electrolytes were obtained for compositions with x= 0.667 and x= 1.333. An improved sinterability was observed with respect to NASICON with conventional composition, which was attributed to liquid-phase sintering. The CO2-gas sensors using these dense samples showed a stable electromotive force (emf) response in dry atmosphere that was similar to the theoretical Nernstian value for a two-electron electrochemical reaction. This was observed also for the NASICON sample with composition x= 1.333 that showed a conductivity far lower than that of the NASICON with conventional composition. The emf changed quickly with changes of the CO2-gas concentration, and steady-state values were observed. The response time, in adsorption and desorption of CO2, was very fast, especially at high CO2concentrations. The influence of humidity on the CO2-sensing performance was investigated. A lower sensitivity and slower response were obtained in humid CO2gas, especially at low CO2concentrations. CO2-sensing measurements at various gas-flow rates were performed to evaluate the reactions occurring at the measuring electrode. The occurrence of a side reaction on the measuring electrode was observed, i.e., the formation of sodium oxides. In dry gas, the reaction took place at low CO2concentrations and small flow rates, whereas the reaction was strongly enhanced in humid environments and occurred over the entire CO2concentration range. However, the sensor performance recovered after switching from humid gas to dry gas. This demonstrated that the humidity affects the emf because of the Na2Oxformation at the electrode, and, thus, the solid electrolyte itself was not degraded by humidity.