An ammonia gas sensor is disclosed that includes a reference electrode, an ammonia selective sensing electrode and an electrolyte disposed therebetween. The ammonia sensing electrode comprises an oxide material characterized by the formula CewAxLyVOz wherein L is lanthanum or another lanthanide element other than cerium, A is one or more other metals, and w, x, y and z are numbers indicative of atomic proportion with w ranging from about 0.001 to about 4 x ranging from 0 to about 0.8, y ranging from about 0.001 to about 4, and z with a range to balance the existence of Cew, Ax, Ly and V.