Abstract
Nanocrystalline perovskite-type BaSnO3 was obtained via microwave-assisted hydrothermal route followed by annealing at variable temperature. The samples composition and microstructure were characterized. Particle size of 18–23 nm was unaffected by heat treatment at 275–700 °C. Materials DC-conduction was measured at variable temperature and oxygen concentration. Barium stannate exhibited n-type semiconductor behavior at 150–450 °C with activation energy being dependent on the materials annealing temperature. Predominant ionosorbed oxygen species types were estimated. They were shown to change from molecular to atomic species on increasing temperature. Comparative test of sensor response to various inorganic target gases was performed using nanocrystalline SnO2-based sensors as reference ones. Despite one order of magnitude smaller surface area, BaSnO3 displayed higher sensitivity to SO2 in comparison with SnO2. DRIFT spectroscopy revealed distinct interaction routes of the oxides surfaces with SO2. Barium-promoted sulfate formation favoring target molecules oxidation was found responsible for the increased BaSnO3 sensitivity to ppm-range concentrations of SO2 in air.
Highlights
Semiconductor metal oxide (SMOx ) based gas sensors suffer from the lack of selectivity to target gases
The powder yielded from hydrothermal treatment of barium-tin hydroxide consisted of BaSn(OH)6 phase with crystallite size dXRD = 21–27 nm (Figure 1a)
Cubic perovskite-type barium stannate was synthesized via aqueous coprecipitation with microwave-assisted hydrothermal treatment
Summary
Semiconductor metal oxide (SMOx ) based gas sensors suffer from the lack of selectivity to target gases. Its fundamental reason might be that typically utilized n-type wide band gap binary oxides, such as ZnO, WO3 , In2 O3 and most often SnO2 [1], possess a confined variety of active sites on the surface These include lattice cations and anions, oxygen vacancies, adsorbed oxygen and hydroxyl species [2]. With the development of wet-chemistry synthetic routes under mild conditions, e.g., hydrothermal [25,26,27,28] and lyothermal [29], ion exchange [30], coprecipitation [31] or polymerized complex methods [11,32], BaSnO3 was found advantageous for other applications The latter include infrared luminescence [18], photovoltaics [27], thermoelectric materials [11], humidity detection [17,33] and resistive gas sensors. An increased SO2 sensitivity of BaSnO3 that exceeded that of tin dioxide was observed for the first time and its origin was studied by in situ diffuse reflectance infrared spectroscopy
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