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

Solid electrolyte type ammonia (NH3) gas sensors were fabricated using Al3+ion conducting (Al0.2Zr0.8)20/19Nb(PO4)3solid 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)2SO4or La2O2SO4–NH4H2PO4auxiliary sensing electrodes exhibited a quantitative and theoretical NH3sensing performance at 230–300 or 170–190 °C, respectively; therefore, sensors based on the (Al0.2Zr0.8)20/19Nb(PO4)3solid electrolyte are expected to be promising candidates as NH3detectors that can operate in a wide temperature range of 170–300 °C by changing the auxiliary sensing electrode component.