Tin oxide thick film by doping rare earth for detecting traces of CO2: Operating in oxygen-free atmosphere

Abstract SnO 2 thick films doped with atomic ratios ranging from 0 up to 8 at.% La, 8 at.% Gd, 8 at.% Lu were fabricated, respectively, via hydrothermal and impregnation methods. The crystal phase, morphology, and chemical composition of the SnO 2 -based nanoparticles were characterized by XRD, FE-SEM, EDX, HRTEM and XPS. Sensing properties of La-SnO 2 , Gd-SnO 2 , Lu-SnO 2 films, as well as the pure SnO 2 film, were analyzed toward CO 2 in the absence of O 2 . It was found that the optimal doping element was La and the best doping ratio was 4 at.%. The maximum response appeared at an operating temperature of 250 °C, on which condition the 4 at.% La-SnO 2 exhibited a remarkable improvement of response from 5.12 to 29.8 when increasing CO 2 concentration from 50 to 500 ppm. Furthermore, the working mechanism underlying such enhancement in CO 2 -sensing functions by La additive in the absence of O 2 was proposed and discussed.