Development of Ammonia Gas Sensors Based on Trivalent Al3+ Cation Conducting Solid Electrolyte

Abstract

Abstract Solid electrolyte type ammonia (NH3) gas sensors were fabricated using Al3+ ion conducting (Al0.2Zr0.8)20/19Nb(PO4)3 solid electrolyte with an aluminum thin film as a reference electrode. A rare-earth ammonium sulfate double salt of R2(SO4)3·(NH4)2SO4 (R = rare earth) or a lanthanum oxysulfate La2O2SO4-based solid solution was selected as the auxiliary sensing electrode on the basis of thermal stability or water durability. Both sensors with R2(SO4)3·(NH4)2SO4 or La2O2SO4–NH4H2PO4 auxiliary sensing electrodes exhibited a quantitative and theoretical NH3 sensing performance at 230–300 or 170–190 °C, respectively; therefore, sensors based on the (Al0.2Zr0.8)20/19Nb(PO4)3 solid electrolyte are expected to be promising candidates as NH3 detectors that can operate in a wide temperature range of 170–300 °C by changing the auxiliary sensing electrode component.