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)(20/19)Nb-(PO4)(3) solid electrolyte with an aluminum thin film as a reference electrode. A rare-earth ammonium sulfate double salt of R-2(SO4)(3)center dot(NH4)(2)SO4 (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 R-2(SO4)(3)center dot (NH4)(2)SO4 or La2O2SO4-NH4H2PO4 auxiliary sensing electrodes exhibited a quantitative and theoretical NH3 sensing performance at 230-300 or 170-190 degrees C, respectively; therefore, sensors based on the (Al0.2Zr0.8)(20/19)Nb(PO4)(3) solid electrolyte are expected to be promising candidates as NH3 detectors that can operate in a wide temperature range of 170-300 degrees C by changing the auxiliary sensing electrode component.