Enhanced Electrode Kinetics in Electrochemical CO₂ and SO₂ Gas Sensors with Ferroelectric Dispersed Composite

The demand for reliable and economical SO ₂ and CO ₂ gas sensors with a large detection range, high sensitivity, good selectivity, rapid response and high accuracy has become evident. In addition, these gases are very difficult to detect by conventional gas sensors for the reason of its high stability at ordinary temperatures. Many kinds of compact sensors using various materials, such as solid electrolytes, mixed oxides, zeolites, and so on have been investigated so far. None of them seems to have achieved sufficient performance characteristics for practical use. Among these, solid electrolytes based sensors are of particular interest again from the viewpoint of low-cost, simple structure, high sensitivity and simplicity of above mentioned gas detection mechanism.

The electrochemical SO ₂ and CO ₂ gas sensors are made using ferroelectric materials dispersed sulphate and carbonate electrolytes, respectively. The performance of sensing electrode sensors is improved due to use of ferroelectric materials with proper proportion. Also, both the response time and the recovery time are found decreased considerably, i.e. sensors quickly respond to change in gas concentration. The ferroelectric property of second phase not only enhances the defect concentration at the grain boundary interface, leading to increase in ionic conductivity, but also promotes oxy-ion activity with improved reaction kinetics. These pronounced effects are discussed in the light of presence of ferroelectric phase in the electrolyte as well as electrodes.

Keywords:

• Electrochemical gas sensor
• gas-solid interface
• kinetics
• ionic conductivity

Acknowledgment

The authors are thankful to Department of Science and Technology, New Delhi for providing financial assistance to carry out this work.

Paper originally presented at AMF-4, Bangalore, India, December 12–15, 2003; received in final form April 10, 2005. The original Proceedings of the Fourth Asian Meeting on Ferroelectricity (AMF-4) are published in seven earlier volumes of FERROELECTRICS (Volumes 323–329, inclusive).