Sensing characterization of Sn/In/Ti nanocomplex oxides for CO, CH4 and NO2

Abstract

The nanocomplex oxides of Sn-In and Sn-In-Ti were prepared by controlled co-precipitation method as sensing materials of semiconductor gas sensors for detection of CO, CH 4 and NO 2 . Through manipulating the Sn/In cation ratio, metal salt total concentration, precipitation pH value and aging time, the nanocrystalline powders were successfully derived with chemical homogeneity and superior thermal stability, compared with the single component oxides. The particle size and morphology, surface area, and thermal and phase stabilities were characterized using TEM, TG-DTA, BET and XRD. The sensing tests showed that the Sn-In composites exhibit high sensitivity and selectivity for CO and NO 2 . The introduction of TiO 2 enhanced CH 4 sensitivity and selectivity, particularly, additives of Pd and Al 2 O 3 as a dopant and surface modification greatly enhanced the sensing properties. The sensitivity depended on the composition of composites, calcination temperature and operating temperature. The optimal values were (25%In 2 O 3 -75%SnO 2 )-20%TiO 2 for ternary composite, 600 and 300℃, respectively. Temperature-programmed desorption (TPD) studies were employed to explain the gas adsorption behavior displayed by the surface of nanocomposites and X-ray photoelectron spectroscopic (XPS) analysis was used to confirm the electronic interactions existing between oxide components. The sensing mechanism of the nanocomposites was attributed to chemical and electronic synergistic effects.