Highly water vapor-durable solid electrolyte type ammonia gas sensor with ammonium rare earth niobate as an auxiliary sensing electrode

Abstract

A solid electrolyte-type ammonia (NH₃) gas sensor with high durability for water vapor was devised by combining a trivalent Al³⁺ ion-conducting solid electrolyte and ammonium lanthanum niobate (NH₄LaNb₂O₇). The present sensor, using NH₄LaNb₂O₇ as the auxiliary sensing electrode, detected NH₃ gas concentration by obeying the theoretical Nernst relationship even at 180 °C. The present sensor exhibited a quantitative response to NH₃ gas concentration change without the influence of water vapor even in a highly humid atmosphere containing 4.2 vol % H₂O for over 3 months, indicating that the sensor with the NH₄LaNb₂O₇ auxiliary sensing electrode was revealed to possess an extraordinarily high water vapor durability.