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°C for 30 min. The CrO₃ is known to be unstable above 197°C and transform into Cr₂O₃ upon firing above 197°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°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.