No abstract

No abstract

No abstract

The study presents CeO 2 particles synthesized by the microwave-assisted hydrothermal method using different synthesis times for the analysis of sensitivity to carbon monoxide gas, aiming at its application as a sensor material to prevent poisoning caused by this highly toxic gas. Structural, morphological and spectroscopic and electrical behaviors were analyzed by X-ray diffraction, Rietveld refinement, transmission electronic microscopy, Raman scattering spectroscopy, optoelectronic characterization chamber and FT-IR. The samples presented fluorite-type cubic structures, increase in crystallinity and particle size with the variation synthesis time from 5 to 8 minutes. From the micrographs it was observed that the nanoparticles initially were spherical with a surface domain (200), and the synthesis time made them cubic/polyhedral with a surface (111), showing differences in defects and influencing in its properties. The sample synthesized at 8 minutes showed the best result with response and recovery time of 16 and 2 seconds, respectively, at 390 °C, therefore promising for the fabrication of CO gas selective sensing device.

Low resistive electrodes based on Co and Mo co-doped SnO2 were prepared by the conventional solid-state reaction and sintered at 1250?C for 2 h. Concentration of Co2O3 precursor was unchanged (1mol%), while MoO3 was varied (0.25, 0.50 to 0.75mol%) to promote conductivity. The structural and microstructural characterization revealed that the samples have a rutile-type structure without secondary phases and large rutile grains with low porosity. Electrical measurements on DC mode have shown a semiconductor behaviour of the SnO2 samples doped with 0.25 and 0.75 at.% of Mo at temperatures below 50K, indicating their suitability for low-temperature electronic applications. Impedance measurements indicate reduced energy barriers of less than 1meV formed between highly conductive crystallites for the SnO2 samples doped with 0.25 and 0.75 at.% of Mo. The sample with Mo content of 0.50 at.% presented a higher energy barrier at a few hundredths of eV, with space charges at the crystallite boundaries.