Response to humidity of TiO2 : WO3 sensors doped with V2O5: Influence of fabrication route

Nowadays, semiconducting metal oxides humidity sensors are applied in many areas: regarding Relative Humidity ( RH) measurement, the electronic/ionic charge transfer reactions that take place at the semiconductor surface and inside the pores, for which the overall conduction mechanisms are highly influenced by the sensing material physical/chemical properties. In a previous paper, the influence of different contents of V2O5, 3, 5 and 7% in weight in sensors based on the TiO2: WO3 pair sintered at 700 degrees C was investigated. Since V2O5 as a low melting point (similar to 690 degrees C), authors decided to alter the fabrication procedure: mechanical alloying was applied to the as received starting powders, allowing the reduction of the sintering temperature to 500 degrees C, and sensors based on the TiO2: WO3 pair, with 3, 5 and 7% in weight content of V2O5, were prepared. The present paper describes the influence that the change of fabrication steps had on the new sensors response to moisture: some of the sensors present a conduction type transition, and were investigated concerning microstructural characterization and their electrical response was measured in the range 400 Hz-40 MHz, at the operating temperature of 20 degrees C and on the relative humidity (RH) range between 10 and 100%. Besides, a model of the sensors electrical behaviour is depicted, which permits to better comprehend the phenomena's present in our sensors that contribute to the overall electrical response. (C) 2016 Published by Elsevier B.V.