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Yttria-stablized zirconia (YSZ)-based mixed-potential type NH 3 sensors using Mg 2 Cu x Fe 1 O 3.5+ x mixed metal oxides ( x =0, 0.25, 0.50, 1) as sensing electrode material were fabricated for ammonia (NH 3 ) detection at different working temperatures ( T =350 °C, 400 °C, 450 °C, 500 °C). The Mg 2 Cu x Fe 1 O 3.5+ x electrodes were characterized by X-Ray Diffraction (XRD), Environmental Scanning Electron Microscope (ESEM), Energy Dispersive Spectrometer (EDS) and the Brunauer–Emmett–Teller (BET) method. The effects of Cu-content on phase composition, microstructures, NH 3 response performances and electrochemically catalytic-activity of Mg 2 Cu x Fe 1 O 3.5+ x electrodes were discussed. Magnesium copper oxide (Mg 0.78 Cu 0.22 O) may be a functional phase that improved NH 3 sensitivity of Mg 2 Cu x Fe 1 O 3.5+ x electrodes, but magnesium dicopper oxide (Cu 2 MgO 3 ) played an opposite role as a suppressive phase. The Mg 2 Cu 0.25 Fe 1 O 3.75 electrode exhibits the biggest response (about 267 mV for 200 ppm of NH 3 ), the highest NH 3 sensitivity (220 mV/decade NH 3 ) and the highest electrochemically catalytic-activity may be attributed to its suitable Cu-content for functional phase (Mg 0.78 Cu 0.22 O) with higher NH 3 adsorptivity, which can absorb more NH 3 to the triple-phase boundary (TPB) for the electrochemically reaction. [ABSTRACT FROM AUTHOR]

Mg 2 Cu 0.25 Fe 1 O 3.75 mixed metal oxides have been synthesized by a co-precipitation method for fabricating NH 3 sensors electrodes. The sensor electrodes were sintered at 1000 °C, 1100 °C, 1200 °C, and 1300 °C to obtain different electrode microstructures. The electrodes were characterized by X-ray diffraction (XRD), the Brunauer–Emmett–Teller (BET) method and Environmental Scanning Electron Microscope (ESEM). NH 3 response performances of the NH 3 sensors to different concentrations of test gases (20–400 ppm NH 3 ) were evaluated at 400 °C. The influences of sintering temperature on the microstructures, NH 3 sensing performances, and electrochemically catalytic activity of Mg 2 Cu 0.25 Fe 1 O 3.75 electrodes were investigated. The electrode sintered at 1200 °C exhibited the biggest response (about 110 mV for 400 ppm NH 3 ) and the highest NH 3 sensitivity (72 mV/decade NH 3 ) of all the electrodes. Moreover, the response time and recovery time were within 8–4 s and 8–14 s, respectively. The enhanced NH 3 sensing performances of the Mg 2 Cu 0.25 Fe 1 O 3.75 electrodes may be attributed to electrodes׳ larger electrochemically catalytic activity and more quantity of triple-phase boundary (TPB) of the sintered three-dimensional network electrode structure. [ABSTRACT FROM AUTHOR]