Effect of Al<sub>2</sub>O<sub>3</sub>in Porous Zirconia Electrolytes for NO Sensing

Kharashi, Khawlah; Murray, Erica Perry

doi:10.1149/2.0761613jes

Cited by 8 publications

(12 citation statements)

References 23 publications

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“…Accumulation of various molecules at the electrode/electrolyte interface can also enable undesirable reactions to proceed leading to cross-sensitivity. The impact of water cross-sensitivity has been ambiguous as it can cause the NO x sensing response to increase or decrease [4][5][6]. Some studies suggest that the different behavior observed is related to the sensor materials, fabrication methods, and operating conditions.…”

Section: Introductionmentioning

confidence: 99%

Managing H2O Cross‐Sensitivity Using Composite Electrolyte NOx Sensors

Murray¹,

Kharashi²,

Adedeji³

2017

Electrochemical Sensors Technology

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NO x sensors composed of partially stabilized zirconia (PSZ), fully stabilized zirconia (FSZ), and PSZ-FSZ composite electrolytes were investigated using impedance spectroscopy under dry and humidified gas conditions. The impedance data were used to interpret the electrochemical behavior of the various sensors as the water concentration in the gas stream varied. The sensors were operated in the presence of 0-100 ppm NO with 1-18% O 2 and 3-10% H 2 O with N 2 as the balance gas. The operating temperature of the sensors ranged from 600 to 700 C. The impedance response for sensors containing ≥ 50 vol% PSZ slightly decreased under humidified gas conditions, in comparison to dry gas conditions; whereas, a significant increase in impedance occurred for sensor largely containing FSZ. This indicated water cross-sensitivity was substantial at FSZbased sensors. The microstructural properties, NO x sensitivity, oxygen partial pressure and temperature dependence, as well as the response time of the sensors composed of the various electrolytes were characterized in order to interpret the electrochemical response with respect to water cross-sensitivity. Analysis of the data indicated that sensors composed of a PSZ-FSZ composite electrolyte with 50 vol% PSZ were more suitable for detecting NO x while limiting water cross-sensitivity.

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Section: Introductionmentioning

confidence: 99%

Managing H2O Cross‐Sensitivity Using Composite Electrolyte NOx Sensors

Murray¹,

Kharashi²,

Adedeji³

2017

Electrochemical Sensors Technology

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“…The impedance describing the high-frequency data, Z HF , in the equivalent circuit model of FSZ composite electrolyte is described by the following complex equation [ 22 , 24 , 32 , 61 ]:

where j = √−1, ω = 2πf, and f is the sensor operating frequency. The non-ideality factor, n, determines the fit of Q HF and represents the depressed semicircle nature of the arc in the porous electrolyte.…”

Section: Resultsmentioning

confidence: 99%

“…Among the limited studies relevant to sensing NO x, it has been reported that adding low amounts (i.e., 0.5–2 wt%) of Al 2 O 3 to YSZ removes SiO 2 impurities from grain boundaries, thereby facilitating ionic conductivity along the grain boundaries [ 20 , 21 ]. Porous composite electrolyte supported NO x sensors evaluated by Kharashi et al found that adding 2 wt% Al 2 O 3 to the partially stabilized zirconia (PSZ) electrolyte promoted greater NO x sensitivity compared to the non-composite PSZ supported sensors [ 22 ]. Increasing the Al 2 O 3 concentration beyond 2 wt% adversely impacted sensor sensitivity to NO as the insulating properties of Al 2 O 3 became apparent [ 23 ].…”

Section: Introductionmentioning

confidence: 99%

“…The composite NO x sensors included a porous composite electrolyte composed of fully stabilized and partially stabilized ZrO 2 (i.e., FSZ and PSZ) along with Al 2 O 3 . The authors selected these materials, as prior studies suggested that composite electrolytes contributed to greater NO x sensing capabilities, along with reduced water cross-sensitivity [ 22 , 24 ]. To the authors’ knowledge, other studies have not evaluated the behavior of NO x sensors entirely composed of composite materials.…”

Section: Introductionmentioning

confidence: 99%

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Investigation of an Impedimetric LaSrMnO3-Au/Y2O3-ZrO2-Al2O3 Composite NOx Sensor

et al. 2022

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Composite NOx sensors were fabricated by combining partially and fully stabilized yttria-doped zirconia with alumina forming a composite electrolyte, Y2O3-ZrO2-Al2O3, and strontium-doped lanthanum manganese oxide mixed with gold to form the composite sensing electrode, La0.8 Sr0.2MnO3-Au. A surface chemistry analysis of the composite sensor was conducted to interpret defects and the structural phases present at the Y2O3-ZrO2-Al2O3 electrolyte, as well as the charge conduction mechanism at the LaSrMnO3-Au electrode surface. Based on the surface chemistry analysis, ionic and electronic transport properties, and microstructural features of sensor components, the working principle was described for NOx sensing at the composite sensor. The role of the composite materials on the NOx sensing response, cross-sensitivity to O2, H2O, CO, CO2, and CH4, and the response/recovery rates relative to sensor accuracy were characterized by operating the composite NOx sensors via the impedimetric method. The composite sensors were operated at temperatures ranging from 575 to 675 °C in dry and humidified gas environments with NO and NO2 concentrations varying from 0 to 100 ppm, where the balance gas was N2. It was found that the microstructure of the composite NOx sensor electrolyte and sensing electrode had a significant effect on interfacial reactions at the triple phase boundary, as well as the density of active sites for oxygen reactions. Overall, the composite NOx sensor microstructure enabled a high NOx sensing response, along with low cross-sensitivity to O2, CO, CO2, and CH4, and promoted NO detection down to 2 ppm.

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“…Analysis of the elec-trochemical responses of the 50PSZ-50FSZ-based sensors indicated PSZ contributed to lower water cross-sensitivity, while FSZ promoted NO x sensitivity. Finally, sensors composed of the 50PSZ-50FSZ composite electrolyte demonstrated signiicant sensitivity to NO and low crosssensitivity to water with negligible temperature dependence [32][33][34][35].…”

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confidence: 98%