Many studies have been carried out concerning the development of SO2 sensors to detect and avoid its
health prejudicial effects. However, there is still a lack of reliable, high-speed-response sensors that work
at room temperature. In this work, the segregation of Ni in the SnO2−NiO system is used to obtain a
rapid SO2 sensor response. Segregation and its structure consequences were studied by electron dispersive
spectroscopy, infrared spectroscopy, and high-resolution transmission electron microscopy in nanopowders
of SnO2−NiO with different compositions prepared by a polymeric precursor method. The sensor activity
of SnO2−1 mol % Ni was studied and a linear calibration curve was formed with a maximum limit
response of 32 ppm SO2.
Ni-doped SnO 2 nanoparticles, promising for gas-sensing applications, have been synthesized by a polymer precursor method. X-ray diffraction (XRD) and transmission electron microscopy (TEM) data analyses indicate the exclusive formation of nanosized particles with rutile-type phase (tetragonal SnO 2 ) for Ni contents below 10 mol%. The mean crystallite size shows a progressive reduction with the Ni content. Room-temperature Raman spectra of Ni-doped SnO 2 nanoparticles show the presence of Raman active modes and modes activated by size effects. From the evolution of the A 1g mode with the Ni content, a solubility limit at ∼2 mol% was estimated. Below that content, Raman results are consistent with the occurrence of solid solution (ss) and surface segregation (seg.) of Ni ions. Above ∼2 mol% Ni, the redshift of A 1g mode suggests that the surface segregation of Ni ions takes place. Disorder-activated bands were determined and their integrated intensity evolution with the Ni content suggest that the solid-solution regime favors the increase of disorder; meanwhile, that disorder becomes weaker as the Ni content is increased.
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