Search

Abstract A spinel-type metal oxide NiFe 2 O 4 prepared by solid state synthesis was utilized as sensing electrode on a YSZ (yttria stabilization zirconia) based mixed potential NO 2 sensor. NO 2 sensing performances were evaluated at an operating temperature range of 350–500 °C. The sensor exhibited maximum response (81.3 mV to 100 ppm NO 2) at 400 °C and optimal sensitivity of 82.8 mV/decade at 450 °C. Both cycling response and cross-sensitivity were evaluated, indicating good stability and selectivity. Furthermore, the EIS (electrochemical impedance spectrum) was also investigated to claim its sensing mechanism. [ABSTRACT FROM AUTHOR]

Na 0.5 Bi 0.5 TiO 3 (NBT) based oxide-ion conductor ceramics have great potential applications in intermediate-temperature solid oxide fuel cells (SOFCs) and oxygen sensors. Na 0.5 Bi 0.49 Ti 1−x Mg x O 3−δ ceramics with x=0, 0.01, 0.02, 0.03, 0.05 and 0.08 were prepared by conventional solid-state reaction. XRD measurement and SEM analysis revealed the formation of pure perovskite structures without secondary phase. MgO doping greatly decreased the sintering temperature and inhibited grain growth. AC impedance spectroscopy measurement was adopted to measure the total conductivity, which was found to increase with MgO doping content ranging from 0 to 3 mol% and subsequently to decrease. High oxygen ionic conductivity σ t =0.00629 S/cm was achieved for sample doped with 3 mol% MgO at 600 °C in air atmosphere. [ABSTRACT FROM AUTHOR]

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]

In this work, a (La0.8Sr0.2)2FeNiO6−δ (LSFN) powder semiconductor oxide with a double-perovskite structure was synthesized by a polymeric precursor method to fabricate a sensitive electrode (SE) for a NO x sensors based on yttria-stabilized zirconia (YSZ). The LSFN powder and the LSFN-SEs sintered at different temperatures (1000, 1100 and 1200°C) were characterized by X-ray diffraction (XRD). The morphologies of LSFN-SEs were observed by environmental scanning electron microscopy (ESEM). The sensors with LSFN-SEs were tested over a temperature range of 550–800°C. Electrochemical impedance spectroscopy (EIS) was also performed to investigate the electrochemical processes that are affected by the NO2 concentration. The results demonstrated that the double-perovskite type electrode material possessed good thermal stability. The NO2 sensitivity of the sensor was found to be modulated by the morphology of LSFN–SE. The sensor showed a higher sensitivity and a better selectivity to NO2 than that to NO. The impedance changed when the NO2 concentration was varied, which was attributed to the interaction of the NO2 with the SE. [ABSTRACT FROM AUTHOR]

Abstract: Poly(ethylene glycol)(400)dimethacrylate (PEG(400)DMA) was used as main binder and cross-linker to gelcast 3YSZ, while acrylamid (AM) as minor monomer. Influences of PEG(400)DMA and dispersant content on rheological property (including zeta potential and viscosity) of the slurry as well as on the flexural strength of green body were discussed. Effect of PEG(400)DMA on surface exfoliation of green body gelcast in air was also investigated. Zeta potential of the slurry was significantly affected by PEGDMA after substituting PEGDMA for AM. Improved rheological property and flexural strength of green body were obtained by adding 1.35wt% dispersant to slurry. Flexural strength of green body prepared by 45vol% solid loading slurry reached 18.7MPa at 6.5wt% monomer concentration. Surface exfoliation of green body was eliminated when slurry was solidified in air at 70°C with 3.5wt% PEG(400)DMA/AM in slurry. [Copyright &y& Elsevier]