Formation and dissociation of excitons in La3+-doped BaSnO3 and improvement of ethanol sensitivity: Heating, nano-CdSnO3 decoration and UV illumination

Crystalline (Ba1-xLax)SnO3 micron sheets and amorphous CdSnO3 nanospheres were prepared by dehydrating their precursors. The doping of La3+ results in the formation of localized excitons, which are composed of positively charged La•Ba (La+) and negatively charged oxygen vacancies (V′). These excitons cause the blue shift of UV absorption and the improvement of ethanol sensitivity for pure BaSnO3. CdSnO3 sample exhibits a broad UV absorption and its decoration can make (Ba1-xLax)SnO3 sample red shift. The (Ba0.93La0.07)SnO3 sample is more sensitive to ethanol at 500 ppm than other samples, with a maximum gas response (Rmax) of 205.0 at 240 °C. CdSnO3 decoration can reduce the operating temperature of (Ba0.93La0.07)SnO3 sensor under 385 nm UV light, achieving a Rmax of 132.1 at 160 °C for the same gas concentration. The improvement of ethanol sensitivity is owing to the thermal and UV dissociation of localized excitons, which are discussed detailedly in this paper.