Novel design and preliminary results of YSZ electrolyte-based amperometric oxygen sensors

The increasing necessity of reducing harming emissions in exhaust gases has spurred on the development of robust and long living gas sensors capable to work in very aggressive environments (Duk-Dong Lee and Dai-Sik Lee, 2001). In this respect, oxygen sensors take a very important role in the control of the oxygen-to-fuel ratio in the mixture of combusting engines (Tifee et al., 2001). High temperature electrochemical sensors based on solid electrolytes have been the subject of much research in the last 20 years, leading to very successful industrial applications. Nevertheless, many improvements are still required in matter of roughness, long term stability, detection range and response speed. In the present work, a novel design and fabrication method of an amperometric oxygen sensor have been developed. Its main originality entails the use of an yttria stabilized zirconia (YSZ) porous layer which acts both as an oxygen conductor (electrolyte) and as a gas diffusion barrier. The electrodes were deposited using a commercial platinum paste. The entire device has been fabricated by means of an optimized screen printing method. The exclusive use of this innovative technique has permitted the implementation of a very compact planar device in an easy, fast and highly economical way. The sensor has been structurally characterized using SEM, revealing a very uniform-shaped micro-stack. Electrical measurements show a behavior typical of that expected from amperometric oxygen sensors (Garzon, 1998). The device developed with a linear output and a good selectivity in a wide range of oxygen partial pressures. Moreover, the response to changes in the atmosphere composition was almost immediate. Those promising results, joined to the ease of fabrication and scalability, demonstrates the viability of the proposed amperometric oxygen sensor design.