The Fabrication And Study Of Ammonia Sensors Based On Solid Electrolyte

Ammonia is widely used in the industrial and daily life. However, ammonia is a toxic gas. Even a very low concentrations, it still be a threat for human. Therefore, it is a hotspot to research and development ammonia gas sensors, which can monitor the ammonia concentration in real time. Furthemore, it should have the performance of high sensitivity,good selectivity, stable performance and low cost. The mixed-potential NH₃ sensors, based on the solid electrolyte, are used widely due to their advantages of simple structure, no need of reference gas, good stability and selectivity. In this paper, in order to improve the sensor performance, three kinds of mixed-potential NH₃ sensors were fabricated and studied from two aspects of solid electrolyte and sensitive electrode materials.Firstly, a mixed-potential NH₃ sensor based on a Ce0.8Gd0.2O1.9 plate and a WO₃ electrode ?8YSZ-WO₃ sensor? was fabricated and studied. The effects of electrode calcination temperature on the performance of the sensor were studied from the microstructure and properties of the devices obtained at 600 ?, 650 ?, 700 ?and 750 ?.It was found that the sensor had the best performance when the calcination temperature was 700 ?,and the response value of the sensor to 250 ppm NH₃ was -59.35 mV at 550 ?and the sensitivity was 52.65 mV/decade.And then, the influence of the structure of the sensitive electrode material on the sensor performance was studied by using the mesoporous WO₃ instead of the conventional WO₃.The analysis shows that the sensor good test performance between 250-650 ?, the temperature range is wide. It exhibits best performance at 500 ??aboutl64.52 mV for 250 ppm NH₃, and the sensitivity is 118.8 mV/decade?. Due to the unique mesoporous structure,the sensor exhibits a higher NH₃ sensitivity compared to sensors with conventional WO₃ as sensitive electrodes. In addition, it also has good repeatability, stability and selectivity.Finally,a new NH₃ sensor was fabricated using Ce0.8Gd0.2O1.9 instead of 8YSZ solid electrolyte ?GDC-WO₃ sensor?. It is found that GDC-WO₃ sensor has higher NH₃ sensitivity than 8YSZ-WO₃ sensor. Furthemore, it has good selectivity, repeatability and stability.Which indicat that GDC is suitable for use as the electrolyte of mixed potential NH₃ sensors.Electrochemical impedance measurements show that the high oxygen ion conductivity of GDC reduces the charge transfer resistance of TPB, increases the current density, and improves the performance of the gas sensor. In addition, the working mechanism of the sensor is also explored.