Ammonia gas sensing properties of Cr2O3 activated ZrO2 thick film resistors

ZrO2 thick films were prepared by standard screen printing technique. Pure ZrO2 films were activated with Cr3+ by dipping them into an aqueous solution (0.1 M) of chromium trioxide CrO3 for different interval of time 5, 10, 20, 30 minutes and fired at 550 degrees C for 30 min. The CrO3 is known to be unstable above 197 degrees C and transform into Cr2O3 upon firing above 197 degrees C. The grain of Cr2O3 would disperse around the grains of ZrO2 base material. The films were characterized by XRD, SEM, EDAS, UV techniques. The gas sensing performance of different target gases was tested and the chromium activated films dipped in 10 Min. was observed to be sensitive. And highly selective 1000ppm of NH3 gas at operating temperature 300 degrees C. The elemental composition were discussed and effect of Cr3+ concentration on sensitivity, selectivity, response and recovery time of the sensor in the presence of different gases were studied. Reaction mechanism were discussed with better performance could attributed to an optimum number of surface misfrits in terms of Cr2O3 on the ZrO2 films. It was first time observed that crominated surface modified film have reduction in bandwidth and observed activation energy were reported.