Conductivity and mixed conductivity of a novel dense diffusion barrier and the sensing properties of limiting current oxygen sensors

Abstract

First-principles calculations were used to explore the effect of various Y-doping levels on the electrical conductivity of SrTiO₃. Herein, we prepared ((Y_0.07Sr_0.93Ti_0.6Fe_0.4−xO_3−δ)/x/3Co₃O₄ (x = 0.1, 0.2, 0.3)) composites using a solid state reaction method. The properties of these sensing materials and the fabricated sensors including crystal phase composition, microstructures, oxygen ionic conductivity, total conductivity and sensor performance were investigated in detail. XRD demonstrates the formation of a highly cubic perovskite structure. The introduction of Co₃O₄ promotes remarkably the electronic conductivity of the Y_0.07Sr_0.93Ti_0.6Fe_0.4−xO_3−δ/x/3Co₃O₄ composites due to the formation of n-type CoO and p-type Co₂O₃. A limiting current oxygen sensor based on (Y_0.07Sr_0.93Ti_0.6Fe_0.4−xO_3−δ)/x/3Co₃O₄ as a dense diffusion barrier shows excellent sensing performance. The recovery time is less than the response time, indicating that Co₂O₃ promotes the gas desorption reaction which results in a shorter recovery time. The obtained results demonstrate a direct relationship between limiting current (I_L) and oxygen content.