Amperometric solid-state gas sensor using LaGaO₃ based perovskite oxide electrolyte for detecting hydrocarbon in exhaust gas - II. Improvement of inactive electrode performance

LaGaO₃ (LSGM) based solid electrolyte coupled with suitable electrodes was demonstrated to be a highly sensitive hydrocarbon (C ₃H₆) sensor in the temperature range of 523-673 K. Sensors were studied in the amperotnetric mode. Keeping Pt as the active electrode, the various inactive electrode materials were studied. It was seen that La _0.5Sr_0.5CoO₃ (LSC 55) gave the best sensitivity among the studied LaCoO₃ catalysts. Furthermore, it was found that the performance of the sensor with La_0.5Sr_0.5MnO ₃ (LSM 55) showed the highest sensitivity (≈600 μ,A/decade at 623 K) among all the investigated perovskite oxides for an inactive electrode. The sensitivity of all the sensors was fast, reversible, and the current linearly increased with increasing C₃H₆ concentration. Over a broad range of oxygen concentration, the C₃H₆ sensitivity was found unaltered. The thickness of the LaGaO₃ electrolyte played an important role for increasing the sensitivity. The measured value of the open circuit potential in the potentiometric mode was very small; but it confirmed the development of mixed potential between the two electrodes which palyed the key role for changing current in the present amperometric sensor.