CO2 gas sensors based on Yb1-xCaxFeO3 nanocrystalline powders

In this study, the Yb1-xCaxFeO3 (0 <= x0.3) nanocrystalline powders were prepared by sol-gel method. We used the method of quantitative analysis to research the gas-sensitive properties for Yb1-xCaxFeO3 to CO2. Also, we investigated the effects of various factors on gas sensing properties by simple variable method. The doping of Ca could not only decrease the resistance of YbFeO3, but also enhance its sensitivity to CO2. When the Ca content x=0.2, Yb1-xCaxFeO3 showed the best response to CO2. The response R-g/R-a to 5000 ppm CO2 for Yb0.8Ca0.2FeO3 at its optimal temperature of 260 degrees C with the room temperature humidity of 28%RH was 1.85. The response and recovery time decreased with an increase of the operating temperature for Yb0.8Ca0.2FeO3 sensor to 5000 ppm CO2. Furthermore, with an increase of CO2 concentration from 1000 to 50000 ppm, the response time of Yb0.8Ca0.2FeO3 became shorter, and meanwhile the recovery time was longer. CO2-sensing response for Yb0.8Ca0.2FeO3 increased with the increase of relative humidity. The response for Yb0.8Ca0.2FeO3 in the background of air (with the room temperature humidity of 39%RH) at 260 degrees C could reach 2.012 to 5000 ppm CO2, which was larger than the corresponding value (1.16) in dry air.