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

Abstract

La0.8Sr0.2Ga0.8Mg0.2O3–δ (LSGM) and La0.8Sr0.2(Ga0.8Mg0.2)1–xCrxO3–δ (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 four-probe 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 iL(mA)=3.65CO2(%) is established from the measured data by simple regression analysis. The Arrhenius model for limiting current is logiL(mA)=3.11−2.16/T(K), and the activation energy for oxygen diffusion is 0.43 eV.