CO sensitive nanocrystalline LaCoO3 perovskite sensor prepared by high energy ball milling

This paper reports high energy ball milling as a promising nanostructured perovskite synthesis route to develop high sensitive and low cost nano-perovskite gas sensors. CO gas sensing properties of thick film LaCoO3 perovskite prepared by (a) high energy ball milling, (b) sol–gel and (c) solid state reaction have been comparatively studied under 100 ppm CO in dry air at different operating temperatures. Crystallite size, structural morphology, specific surface area, and oxygen desorption properties were investigated by XRD, N2 adsorption–desorption measurements (BET), SEM and TPD-O2, respectively. Compared to the other methods, high energy ball milling resulted in the lowest crystallite size of 11 nm, the highest amount of grain boundary, and the best CO gas sensing properties while the specific surface area of all samples was similar. Mean crystallite size and grain boundary volume were found to affect the gas sensing properties. The results of TPD-O2 and gas sensing experiments confirmed that the response ratio of samples is well correlated with the total amount of desorbed oxygen. The specific surface area (SSA) of BM material was increased via a second milling process. SSA was increased from 4 m2/g to an optimum value of 66 m2/g by performing a 60 min additional milling step. TPD-O2 profiles of modified BM materials support the effect of SSA on oxygen adsorption properties. Improved BM material showed the highest response ratio of up to 75% for 100 ppm CO in dry air at 125 °C, which is four and ten times better than those obtained by sol–gel and solid state reaction methods, respectively.