Effect of Cobalt doping on the microstructure, electrical and ethanol-sensing properties of SmFe1−xCoxO3

SmFe1−xCoxO3(x = 0–1.0) samples were prepared by a sol–gel citrate method. The influence of Co content upon microstructure, electrical and ethanol-sensing properties for SmFe1−xCoxO3 was investigated in detail. The samples show a single-phase orthogonal perovskite structure. The lattice constant, unit cell volume and average grain size decrease with an increase in the Co content due to forming oxygen vacancies in the sample SmFe1−xCoxO3. The sensor response to ethanol increases with increasing the Co2+-doping amount till x = 0.3, where it reaches the highest value, then falls off to a minimum value at x = 0.5, and finally gradually increases. The results indicate that SmFe0.7Co0.3O3 has the maximum response (S = 80.78) to 300 ppm ethanol at 215 °C. The sensitivity factor for formaldehyde, gasoline, methanol and acetone is 12.16, 11.03, 9.53 and 8.29, respectively. The sensor has good selectivity to ethanol vapor and shows good linearity properties in ethanol concentration. What's more, the influence mechanism of Co content upon microstructure, conductivity and response to ethanol were studied in detail.