Impedance characteristics of thin films humidity sensing elements based on Bi - doped TiO 2

The paper proposes results from the investigations of humidity sensing elements based on Bi-doped TiO 2 thin films, prepared by a sol-gel method. Titanium n-butoxide was used as a starting material for the preparation of the experimental samples, and bismuth acetate as doping compound. The samples were sintered at 400°C. Afterwards, the samples were placed into a calibrated humidity chamber and their electrical properties were investigated by a precision impedance analyzer in the frequency range of 20Hz – 5 MHz. The impedance characteristics, impedance spectra and equivalent electrical circuit of the investigated samples were obtained. The influence of Bi-dopant on the impedance characteristics of the samples has been compared with the respective characteristics of the referent samples based on pure TiO 2 , prepared by the same method. The relation between the impedance spectra and the humidity sensing properties of the samples was also explained.