Y-doped CaZrO₃/Co₃O₄ as novel dense diffusion barrier materials for a limiting current oxygen sensor

Herein, we illustrate a feasible strategy to strengthen the gas sensing of Y-doped CaZrO₃ (Y_xCa_1-xZr_0.7O_3-δ (x = 0.05, 0.06, and 0.07))/0.1Co₃O₄ used as sensing materials. This compound was prepared via a solid-state reaction technique. The structural, morphological, electrical, and sensing features such as phase identification, microstructure, ionic conductivity, total conductivity and sensitivity of the fabricated sensors were evaluated via X-ray diffraction, scanning electron microscopy, electron-blocking method, electrochemical impedance spectroscopy and cyclic voltammetry. In addition, the influence of the Y-dopant on the properties of Y_xCa_1-xZr_0.7O_3-δ/Co₃O₄ was thoroughly studied. XRD results revealed the formation of the orthorhombic perovskite phase of Y_xCa_1-xZr_0.7O_3-δ. Moreover, the obtained results from the electrical properties elucidated high electronic and low ionic conductivities, and small polaron conduction of Y_xCa_1-xZr_0.7O_3-δ/Co₃O₄. Furthermore, the results confirmed an excellent limiting current plateau for the fabricated oxygen sensor based on Y_xCa_1-xZr_0.7O_3-δ/Co₃O₄. In particular, experimental observation indicates that Y-doping at the Ca site and/or Zr site might be difficult.