SnO2 nano powders were prepared by solution reduction method using tin chloride(SnCl2·2H2O), hydrazine(N2H4) and NaOH. The SnO2 thick films for gas sensors were fabricated by screen printing method on alumina substrates and annealed at 300℃ in air, respectively. XRD patterns of the SnO2 nano powders showed the tetragonal structure with (110) dominant orientation. The particle size of SnO2 nano powders at the ratio of SnCl2:N2H4+NaOH= 1:6 was about 60 nm. The sensing characteristics were investigated by measuring the electrical resistance of each sensor in a test box. Sensitivity of SnO2 gas sensor to 5 ppm CH4 gas and 5 ppm CH3CH2CH3 gas was investigated for various SnCl2:N2H4+NaOH proportion. The highest sensitivity to CH4 gas and CH3CH2CH3 gas of SnO2 sensors was observed at the SnCl2:N2H4+NaOH= 1:8 and SnCl2:N2H4+NaOH= 1:6, respectively. Response and recovery times of SnO2 gas sensors prepared by SnCl2:N2H4+NaOH= 1:6 was about 40 s and 30 s, respectively.
