An Impedancemetric NH3Sensor Based on La10Si5MgO26Electrolyte and Nano-Structured CoWO4Sensing Electrode

A new type impedancemetric NH3 sensor was fabricated using nano-structured CoWO4 sensing electrode and La10Si5MgO26 (LSMO) electrolyte. The CoWO4 particles with 100 nm in diameter were in-situ prepared in the porous LSMO layer by impregnation method. The properties of the sensor were studied using electrochemical impedance spectroscopy in the temperature range of 400–700°C. The equivalent circuits were designed, with the help of which the measured impedance spectra were fitted to extract the equivalent circuit parameters for a preliminary analysis of the electrochemical sensing mechanism. The results show that the obtained impedance spectra of the sensor under different NH3 concentrations are correlated to the CoWO4 electrode/LSMO/NH3 triple phase boundary (TPB). The response signals defined as (|Z|base-|Z|sample) /|Z|base at a fixed frequency in the low frequency region vary linearly with the NH3 concentrations from 20 to 500 ppm. The sensor also shows good response–recovery characteristics and low cross-sensitivities to the various co-existing gases.