Síntese e caracterização de óxido de cério puro e dopado com manganês para aplicação em sensores de gases

Abstract

In this study, syntheses of cerium oxide (CeO2) nanoparticles with different concentrations of manganese were carried out using the microwave-assisted hydrothermal synthesis technique. In order to obtain different compositions, the nanoparticles were modified following the stoichiometric formulas: Ce1-(3/4x)MnxO2, where x varied in the values of 0.0, 4.0, 8.0, 12.0 in mol. The system was then subjected to a thermal treatment at 100 °C for 8 minutes in a conventional microwave oven, with a constant heating rate of 10 °C/min. The resulting powders were subjected to various characterization techniques to evaluate their properties. These techniques included X-ray diffraction (XRD), Raman scattering spectroscopy, ultraviolet-visible (UV-Vis) absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), field emission scanning electron microscopy (FESEM), positron annihilation lifetime spectroscopy (PALS), thermogravimetry (TG), differential thermal analysis (DTA), and electrical characterization. Both pure CeO2 system and manganese-doped system demonstrated high stability, showing similar diffraction patterns. From the analyses performed, it was possible to establish the response times of the sensors when exposed to CO, where a significant improvement was observed for the system doped with different concentrations of Mn compared to the pure system. The modification with higher Mn content (12%) did not show significant changes in terms of sensor response compared to the lower Mn content (4%), indicating that the lower doping of 4% Mn becomes promising for the application of sensors for carbon monoxide detection.