A limiting current oxygen sensor prepared by a co-pressing and co-sintering technique

摘要

La0.8Sr0.2Ga0.8Mg0.2O3-delta (LSGM) and La0.8Sr0.2(Ga0.8Mg0.2)(1-x)CrxO3-delta (LSGMC, 0.1 = x = 0.9) were synthesized by a solid-state reaction and characterized by X-ray powder diffraction (XRD), thermal expansion, and DC fourprobe method. A limiting current oxygen sensor using LSGM solid electrolyte and LSGMC (x = 0.7) dense diffusion barrier was prepared by a co-pressing and co-sintering technique and the sensing performances were evaluated. XRD shows the presence of a crystal structure in the series belonging to Pm-3m (No. 221) for x = 0-0.9. Electrical conductivity and thermal expansion coefficients first decrease and then increase with increasing x. LSGMC (x = 0.7) is the most suitable ceramic material and is selected as dense diffusion barrier. There is a directly proportional relationship between limiting current and oxygen concentration, and the equation i(L) (mA) = 3.65CO(2) (%) is established from the measured data by simple regression analysis. The Arrhenius model for limiting current is log iL (mA) = 3.11 - 2.16 T (K), and the activation energy for oxygen diffusion is 0.43 eV.