Lithium ion-conducting solid electrolytes Li3AlN2 and Li2SiN2 were investigated as possible electrolytes for nitrogen sensors. The nitride ceramics were synthesized and characterized by SEM, X-ray diffraction a nd a.c. impedance. Thermodynamic measurements were carried out by measuring cell electromotive forces (e.m.f.s) consisting of solid electrolyte tubes sandwiched between Cr/Cr2N and CrN/Cr2N references. The results corresponded to the values given in the literature for this system.