Solid electrolyte type ammonia gas sensor based on trivalent aluminum ion conducting solids

Ammonia gas sensors were fabricated by using trivalent aluminum ion conducting (Al0.2Zr0.8)20/19Nb(PO4)3 solid electrolyte with aluminum metal film as a reference electrode. As the auxiliary sensing electrode material, praseodymium ammonium double sulfate Pr2(SO4)3·(NH4)2SO4 or (NH4)2HPO4 doped La2O2SO4 solid solution, 0.7La2O2SO4–0.3(NH4)2HPO4, was applied from the view points of thermal stability or water durability. The former sensor with Pr2(SO4)3·(NH4)2SO4 showed a rapid response and the latter one with 0.7La2O2SO4–0.3(NH4)2HPO4 exhibited a theoretical response even in a humid atmosphere. Since the present sensors applying Al3+ ion conductor showed such a high sensing performance of rapid response or high durability for water, it is greatly expected to be practical NH3 gas sensors.