A mixed-potential type gas sensor using stabilized zirconia (YSZ) and a sensing electrode (SE) that consists of the new type composite oxide Ni₃V₂O₈was developed for ammonia (NH₃) detection at elevated temperature, such as 650℃. The Ni₃V₂O₈materials were synthesized from Ni(NO₃)₂center dot 6H₂O and NH₄VO₃through the sol-gel method. Ni₃V₂O₈sintered at different temperatures was also characterized using X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM). The present study mainly focused on the effect of sintering temperature of SE materials (800 degrees C, 1000℃, 1200℃on NH₃sensing characteristics. Results showed that the Ni₃V₂O₈calcined at 1000℃exhibited the largest sensitivity in an NH₃concentration range of 50-500 ppm at 650℃. The response for the sensor attached with a Ni₃V₂O₈-SE sintered at 1000℃to 100 ppm of NH₃was approximately -62 mV. Moreover, Delta V almost varied linearly with the logarithm of NH₃concentration in the range of 50-500 ppm, which the slope was -96 mV/decade. Furthermore, the present sensor also displayed small drifts over 30 days and cross-sensitivities in the presence of various interfering gases. The high-sensing characteristics of the sensor attached with a Ni₃V₂O₈-SE sintered at 1000℃to NH₃are explained in terms of the micro-structure of the SE and the high electrocatalytic activities induced by the beneficial effect of the interaction between the Ni and V two metal oxides.