Structure and Gas-sensitive Properties of ZnO-Bi_2O_3 Mixed Thick Films

Needle-shaped ZnO and ellipsoid-shaped Bi2O3 nanoparticles, as raw materials of thick films, were prepared by metallic vapour oxidation, and the obtained Bi2O3 is a mixture of δ and β phases. The phase structure and surface morphology of the thick films based on ZnO, Bi2O3 and ZnO-Bi2O3 mixture were investigated by XRD and SEM, then the resistance and gas sensitivity of the thick films were measured. The results indicate that Bi2O3 films show P-type conductivity and have sensitivity to alcohol and acetone more or less. Compared with ZnO, the sensitivity of ZnO-Bi2O3 to benzene, toluene and xylene is lower, which is relative with the increase of granular sizes and barrier height located at grain boundaries of the thick films. But Bi2O3, maybe as a very low activity catalyst, improves the gas sensitivity of the thick films to alcohol and acetone.