Abstract
Precursor powders of 15 mol% calcia-stabilized zirconia solid electrolytes synthesized by a freeze-drying method, and a sol-gel method, were used to prepare oxygen sensors. Sensor elements were fabricated via uniaxial pressing of the calcined powders and subsequently sintered at 1650 {degree sign}C. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques were used to analyze the microstructure, including the interfaces, grain boundary phases and impurity distribution, etc. The electrical response of the gas sensors to oxygen and the complex impedance in air were investigated at various operating temperatures. The correlations between grain microstructure and the impedance spectra characteristics of the sensors as well as oxygen sensing characteristics are discussed.