Perovskite Electrodes for Zirconia Electrolytic Cells

固体氧化物电解质提供了在高温和反应环境下进行电化学的前景；目前的一个应用是监测燃烧废气流中的氧水平。现有的系统使用多孔金属薄膜沉积在固体电解质上；虽然功能齐全，但这种系统的效率很低，显然是因为只有三相（金属、电解质、气体）边界是活跃的。这项研究试图通过使用对电子和氧离子都具有导电性的金属氧化物来克服这个问题。具体来说，研究了气相与钙钛矿结构的一类电解质镧掺杂锰酸钙（LaxCa1-xMn03）之间的氧交换动力学。电子和离子性质可以通过改变掺杂水平而改变。将这些材料制成有用形式的技术将得到完善。电化学动力学是用稳态和瞬态电化学技术测量的；电导率用交流阻抗法测量；表面化学用程序升温解吸和俄歇选择光谱进行探测。这项研究可能会产生非常广泛的影响。最直接的影响将是使用氧气传感器的系统，包括用于汽车化油器和废气控制以及焚烧的控制系统。这项工作将缩小这些传感器的尺寸，扩大其使用温度范围，并提高其灵敏度。类似的电极也可用于燃料电池、电解槽和其他电化学装置。这项工作也适用于其他高性能陶瓷，特别是密切相关的“缺陷钙钛矿超导体”。

Solid-oixide electrolytes offer the prospect of conducting electrochemistry at high temperatures and in reactive environments; one present application is for monitoring oxygen levels in combustion exhaust streams. Existing systems use porous metallic films deposited on solid electrolytes; while functional, such systems have low effeciency, apparently because only the three-phase (metal, electrolyte, gas) boundary is active. This study seeks to overcome this problem by use of metal oxides that exhibit conductivity for both electrons and oxygen ions. Specifically, the kinetics of oxygen exchange between the gas phase and a family of electrolytes with the perovskite structure, lanthanum-doped calcium manganate (LaxCa1-xMn03), is investigated. Electronic and ionic properties can be varied by changing the doping level. Techniques for preparing these materials in useful forms will be perfected. Electrochemical kinetics are measured using steady-state and transient electrochemical techniques; conductivities are measured using AC impedance methods; and surface chemistry is probed using temperature-programmed desorption and Auger election spectroscopy. This study could have very wide impact. The most immediate impact will be in systems using oxygen sensors including control systems for automotive carburetion and exhaust control, and for incineration. This work should reduce the size, extend the useful temperature range, and improve the sensitivity of these sensors. Similar electrodes should be useful in fuel cells, electrolyzers, and other electrochemical devices. The work is also applicable to other high-performance ceramics, notably the closely related "defect perovskite superconductors."