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|Study on the impedancemetric NO sensor fabricated in thick film technology|
|Keywords: Thick film, perovskite electrode, impedancemetric NO sensor|
|Solid state reaction method was used for the synthesis of praseodymium cobaltite with the perovskite structure. The obtained ceramic powder after ball milling was utilized for preparation of thick film paste which was subsequently screen printed to form electrodes of an impedancemetric NO sensor. Round shaped yttria stabilized zirconia (YSZ) plates, about 1 mm thick, were used as solid electrolyte substrates. These substrates were fabricated from YSZ green tape, employing standard procedures such as cutting, stacking, laminating, and lastly firing. The measurement setup consisted of a vertical type gas flow apparatus and an impedance analyzer. The fabricated impedancemetric sensors were studied for the detection of NO gas in the concentration range from 10 to 200 ppm, at temperatures of 650-750°C. Impedance spectroscopy was performed by applying a small ac signal, of 50 mV, between the sensing electrodes, and then measuring the sensor response in the form of real and imaginary parts of the impedance. During impedance measurements, that took place upon exposure to specific concentration of NO, the gas flow rate and operating temperature were held constant while frequency was swept from 10 mHz to 100 kHz. The lower frequency range, approximately below 1 Hz, was found to be crucial for differentiating NO ppm levels. In the Nyquist plots, two arcs can be distinguished – a bigger one attributed to the response of perovskite electrodes and a smaller one related to the response of solid electrolyte-electrode interface. With intent to alter the frequency of interest, sensors of the same configuration but with small variations in geometry of the electrodes were additionally investigated.|
|Katarina Cvejin, Early Stage Researcher
Institute of Electron Techonology, Krakow Division