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Zirconia‐Based Electrochemical NO x Sensors with Semiconducting Oxide Electrodes
Author(s) -
Bartolomeo Elisabetta,
Grilli Maria Luisa,
Yoon Jong Won,
Traversa Enrico
Publication year - 2004
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.2004.tb06335.x
Subject(s) - materials science , electrode , dielectric spectroscopy , oxygen sensor , semiconductor , oxide , electrolyte , analytical chemistry (journal) , electrochemistry , electromotive force , nernst equation , linear sweep voltammetry , resistive touchscreen , optoelectronics , cyclic voltammetry , oxygen , chemistry , electrical engineering , organic chemistry , chromatography , metallurgy , engineering
Electrochemical devices based on coupling an oxygen ionic conductor (Y 2 O 3 ‐stabilized ZrO 2 : YSZ) with semiconducting oxides as sensing electrodes were investigated. LaFeO 3 , a p‐type semiconductor, and WO 3 , an n‐type semiconductor, were chosen because of their known good NO 2 ‐sensing properties as resistive‐type sensors. The entire sensors were wholly exposed to the same atmosphere. The electromotive force (EMF) was measured for different NO 2 concentrations and at fixed temperature. The EMF values of both sensors increased in NO 2 atmosphere with a fast response time. The best performance was observed around 450°C for LaFeO 3 ‐based and 650°C for WO 3 ‐based sensors. Moreover, the response of the LaFeO 3 ‐based sensors was found to be strongly affected by the grain size of the powder used for the preparation of the sensing electrode. The polarization curves of all sensors showed a nonlinearity; nevertheless an opposite behavior in the presence of NO 2 gas was observed for the p‐ and n‐ type‐based oxide sensors. The nonlinearity was attributed to the potential drop for LaFeO 3 or increase for WO 3 at the electrode interface. Amperometric measurements, performed at a fixed potential of 1 V, were found in accordance with polarization curves. The electrochemical impedance spectroscopy (EIS) analysis showed that the resistance and reactance at the electrolyte/electrode interface decreased (for LaFeO 3 )/increased (for WO 3 ) on introduction of NO 2 gas, because of the lowering/increasing of the electrode overvoltage.