Limiting current oxygen sensors with La0.8Sr0.2Ga0.8Mg0.2O3-δ electrolyte and La0.8Sr0.2(Ga0.8Mg0.2)1-xCoxO3-δ dense diffusion barrier

A conventional solid-state reaction was used to synthesize La0.8Sr0.2(Ga0.8Mg0.2)xCo1-xO3-δ (LSGMC, x = 0.1, 0.3, 0.5, 0.7, and 0.9) and La0.8Sr0.2Ga0.8Mg0.2O3-δ (LSGM), of which the structure, conductivity, and thermal expansion behavior were investigated by XRD, four-terminal method, and dilatometry. A limiting current oxygen sensor was prepared with LSGM solid electrolyte and La0.8Sr0.2(Ga0.8Mg0.2)0.1Co0.9O3-δ (LSGMC9) dense diffusion barrier. The effects of temperature, oxygen concentration, and thickness of dense diffusion barrier (L) on sensing properties were investigated. XRD results show that cubic and monoclinic phases are identified for LSGM and LSGMC, respectively. Electrical conductivity increases with x. A change of electrical conductivity from semiconductive to metallic conduction is observed for x = 0.5–0.9 with the temperature rise. Thermal expansion coefficients (TECs) increase to a maximum firstly and then decrease with increasing x at temperature from 300 to 1000 °C. I-V curves of oxygen sensor display a good limiting current plateau. The relationship between limiting current and oxygen concentration is linear. The limiting current decreases with increasing L.